Add nullability annotations to core/spring-boot-autoconfigure

See gh-46587

config/checkstyle/checkstyle-suppressions.xml

@@ -90,4 +90,5 @@
 	<suppress files="PemPrivateKeyParser\.java" checks="NoWhitespaceBefore" message="'...' is preceded with whitespace"/>
 	<suppress files="Bindable\.java" checks="NoWhitespaceBefore" message="'...' is preceded with whitespace"/>
 	<suppress files="LambdaSafe\.java" checks="NoWhitespaceBefore" message="'...' is preceded with whitespace"/>
+	<suppress files="ConditionMessage\.java" checks="NoWhitespaceBefore" message="'...' is preceded with whitespace"/>
 </suppressions>

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/AbstractDependsOnBeanFactoryPostProcessor.java

@@ -22,6 +22,8 @@ import java.util.Set;
 import java.util.function.Function;
 import java.util.stream.Collectors;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.BeanFactoryUtils;
 import org.springframework.beans.factory.FactoryBean;
@@ -50,7 +52,7 @@ public abstract class AbstractDependsOnBeanFactoryPostProcessor implements BeanF
 
 	private final Class<?> beanClass;
 
-	private final Class<? extends FactoryBean<?>> factoryBeanClass;
+	private final @Nullable Class<? extends FactoryBean<?>> factoryBeanClass;
 
 	private final Function<ListableBeanFactory, Set<String>> dependsOn;
 
@@ -61,7 +63,7 @@ public abstract class AbstractDependsOnBeanFactoryPostProcessor implements BeanF
 	 * @param dependsOn dependency names
 	 */
 	protected AbstractDependsOnBeanFactoryPostProcessor(Class<?> beanClass,
-			Class<? extends FactoryBean<?>> factoryBeanClass, String... dependsOn) {
+			@Nullable Class<? extends FactoryBean<?>> factoryBeanClass, String... dependsOn) {
 		this.beanClass = beanClass;
 		this.factoryBeanClass = factoryBeanClass;
 		this.dependsOn = (beanFactory) -> new HashSet<>(Arrays.asList(dependsOn));
@@ -75,7 +77,7 @@ public abstract class AbstractDependsOnBeanFactoryPostProcessor implements BeanF
 	 * @since 2.1.7
 	 */
 	protected AbstractDependsOnBeanFactoryPostProcessor(Class<?> beanClass,
-			Class<? extends FactoryBean<?>> factoryBeanClass, Class<?>... dependencyTypes) {
+			@Nullable Class<? extends FactoryBean<?>> factoryBeanClass, Class<?>... dependencyTypes) {
 		this.beanClass = beanClass;
 		this.factoryBeanClass = factoryBeanClass;
 		this.dependsOn = (beanFactory) -> Arrays.stream(dependencyTypes)

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/AutoConfigurationExcludeFilter.java

@@ -19,12 +19,15 @@ package org.springframework.boot.autoconfigure;
 import java.io.IOException;
 import java.util.List;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.beans.factory.BeanClassLoaderAware;
 import org.springframework.boot.context.annotation.ImportCandidates;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.core.type.classreading.MetadataReader;
 import org.springframework.core.type.classreading.MetadataReaderFactory;
 import org.springframework.core.type.filter.TypeFilter;
+import org.springframework.util.Assert;
 
 /**
  * A {@link TypeFilter} implementation that matches registered auto-configuration classes.
@@ -35,9 +38,10 @@ import org.springframework.core.type.filter.TypeFilter;
  */
 public class AutoConfigurationExcludeFilter implements TypeFilter, BeanClassLoaderAware {
 
+	@SuppressWarnings("NullAway.Init")
 	private ClassLoader beanClassLoader;
 
-	private volatile List<String> autoConfigurations;
+	private volatile @Nullable List<String> autoConfigurations;
 
 	@Override
 	public void setBeanClassLoader(ClassLoader beanClassLoader) {
@@ -66,6 +70,7 @@ public class AutoConfigurationExcludeFilter implements TypeFilter, BeanClassLoad
 			ImportCandidates importCandidates = ImportCandidates.load(AutoConfiguration.class, this.beanClassLoader);
 			this.autoConfigurations = importCandidates.getCandidates();
 		}
+		Assert.state(this.autoConfigurations != null, "'autoConfigurations' must not be null");
 		return this.autoConfigurations;
 	}
 

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/AutoConfigurationImportFilter.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.autoconfigure;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.beans.factory.BeanClassLoaderAware;
 import org.springframework.beans.factory.BeanFactoryAware;
 import org.springframework.context.EnvironmentAware;
@@ -54,6 +56,6 @@ public interface AutoConfigurationImportFilter {
 	 * {@code autoConfigurationClasses} parameter. Entries containing {@code false} will
 	 * not be imported.
 	 */
-	boolean[] match(String[] autoConfigurationClasses, AutoConfigurationMetadata autoConfigurationMetadata);
+	boolean[] match(@Nullable String[] autoConfigurationClasses, AutoConfigurationMetadata autoConfigurationMetadata);
 
 }

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/AutoConfigurationImportSelector.java

@@ -32,6 +32,7 @@ import java.util.stream.Collectors;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.Aware;
@@ -89,23 +90,27 @@ public class AutoConfigurationImportSelector implements DeferredImportSelector,
 
 	private final Class<?> autoConfigurationAnnotation;
 
+	@SuppressWarnings("NullAway.Init")
 	private ConfigurableListableBeanFactory beanFactory;
 
+	@SuppressWarnings("NullAway.Init")
 	private Environment environment;
 
+	@SuppressWarnings("NullAway.Init")
 	private ClassLoader beanClassLoader;
 
+	@SuppressWarnings("NullAway.Init")
 	private ResourceLoader resourceLoader;
 
-	private volatile ConfigurationClassFilter configurationClassFilter;
+	private volatile @Nullable ConfigurationClassFilter configurationClassFilter;
 
-	private volatile AutoConfigurationReplacements autoConfigurationReplacements;
+	private volatile @Nullable AutoConfigurationReplacements autoConfigurationReplacements;
 
 	public AutoConfigurationImportSelector() {
 		this(null);
 	}
 
-	AutoConfigurationImportSelector(Class<?> autoConfigurationAnnotation) {
+	AutoConfigurationImportSelector(@Nullable Class<?> autoConfigurationAnnotation) {
 		this.autoConfigurationAnnotation = (autoConfigurationAnnotation != null) ? autoConfigurationAnnotation
 				: AutoConfiguration.class;
 	}
@@ -168,7 +173,7 @@ public class AutoConfigurationImportSelector implements DeferredImportSelector,
 	 * @param metadata the annotation metadata
 	 * @return annotation attributes
 	 */
-	protected AnnotationAttributes getAttributes(AnnotationMetadata metadata) {
+	protected @Nullable AnnotationAttributes getAttributes(AnnotationMetadata metadata) {
 		String name = getAnnotationClass().getName();
 		AnnotationAttributes attributes = AnnotationAttributes.fromMap(metadata.getAnnotationAttributes(name, true));
 		Assert.state(attributes != null, () -> "No auto-configuration attributes found. Is " + metadata.getClassName()
@@ -192,7 +197,8 @@ public class AutoConfigurationImportSelector implements DeferredImportSelector,
 	 * attributes}
 	 * @return a list of candidate configurations
 	 */
-	protected List<String> getCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes) {
+	protected List<String> getCandidateConfigurations(AnnotationMetadata metadata,
+			@Nullable AnnotationAttributes attributes) {
 		ImportCandidates importCandidates = ImportCandidates.load(this.autoConfigurationAnnotation,
 				getBeanClassLoader());
 		List<String> configurations = importCandidates.getCandidates();
@@ -237,10 +243,12 @@ public class AutoConfigurationImportSelector implements DeferredImportSelector,
 	 * attributes}
 	 * @return exclusions or an empty set
 	 */
-	protected Set<String> getExclusions(AnnotationMetadata metadata, AnnotationAttributes attributes) {
+	protected Set<String> getExclusions(AnnotationMetadata metadata, @Nullable AnnotationAttributes attributes) {
 		Set<String> excluded = new LinkedHashSet<>();
-		excluded.addAll(asList(attributes, "exclude"));
-		excluded.addAll(asList(attributes, "excludeName"));
+		if (attributes != null) {
+			excluded.addAll(asList(attributes, "exclude"));
+			excluded.addAll(asList(attributes, "excludeName"));
+		}
 		excluded.addAll(getExcludeAutoConfigurationsProperty());
 		return getAutoConfigurationReplacements().replaceAll(excluded);
 	}
@@ -389,7 +397,7 @@ public class AutoConfigurationImportSelector implements DeferredImportSelector,
 
 		List<String> filter(List<String> configurations) {
 			long startTime = System.nanoTime();
-			String[] candidates = StringUtils.toStringArray(configurations);
+			@Nullable String[] candidates = StringUtils.toStringArray(configurations);
 			boolean skipped = false;
 			for (AutoConfigurationImportFilter filter : this.filters) {
 				boolean[] match = filter.match(candidates, this.autoConfigurationMetadata);
@@ -426,15 +434,18 @@ public class AutoConfigurationImportSelector implements DeferredImportSelector,
 
 		private final List<AutoConfigurationEntry> autoConfigurationEntries = new ArrayList<>();
 
+		@SuppressWarnings("NullAway.Init")
 		private ClassLoader beanClassLoader;
 
+		@SuppressWarnings("NullAway.Init")
 		private BeanFactory beanFactory;
 
+		@SuppressWarnings("NullAway.Init")
 		private ResourceLoader resourceLoader;
 
-		private AutoConfigurationMetadata autoConfigurationMetadata;
+		private @Nullable AutoConfigurationMetadata autoConfigurationMetadata;
 
-		private AutoConfigurationReplacements autoConfigurationReplacements;
+		private @Nullable AutoConfigurationReplacements autoConfigurationReplacements;
 
 		@Override
 		public void setBeanClassLoader(ClassLoader classLoader) {
@@ -488,10 +499,16 @@ public class AutoConfigurationImportSelector implements DeferredImportSelector,
 				.collect(Collectors.toCollection(LinkedHashSet::new));
 			processedConfigurations.removeAll(allExclusions);
 			return sortAutoConfigurations(processedConfigurations, getAutoConfigurationMetadata()).stream()
-				.map((importClassName) -> new Entry(this.entries.get(importClassName), importClassName))
+				.map(this::getEntry)
 				.toList();
 		}
 
+		private Entry getEntry(String importClassName) {
+			AnnotationMetadata metadata = this.entries.get(importClassName);
+			Assert.state(metadata != null, "'metadata' must not be null");
+			return new Entry(metadata, importClassName);
+		}
+
 		private AutoConfigurationMetadata getAutoConfigurationMetadata() {
 			if (this.autoConfigurationMetadata == null) {
 				this.autoConfigurationMetadata = AutoConfigurationMetadataLoader.loadMetadata(this.beanClassLoader);
@@ -501,6 +518,8 @@ public class AutoConfigurationImportSelector implements DeferredImportSelector,
 
 		private List<String> sortAutoConfigurations(Set<String> configurations,
 				AutoConfigurationMetadata autoConfigurationMetadata) {
+			Assert.state(this.autoConfigurationReplacements != null,
+					"'autoConfigurationReplacements' must not be null");
 			return new AutoConfigurationSorter(getMetadataReaderFactory(), autoConfigurationMetadata,
 					this.autoConfigurationReplacements::replace)
 				.getInPriorityOrder(configurations);

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/AutoConfigurationMetadata.java

@@ -18,6 +18,10 @@ package org.springframework.boot.autoconfigure;
 
 import java.util.Set;
 
+import org.jspecify.annotations.Nullable;
+
+import org.springframework.lang.Contract;
+
 /**
  * Provides access to meta-data written by the auto-configure annotation processor.
  *
@@ -40,7 +44,7 @@ public interface AutoConfigurationMetadata {
 	 * @param key the meta-data key
 	 * @return the meta-data value or {@code null}
 	 */
-	Integer getInteger(String className, String key);
+	@Nullable Integer getInteger(String className, String key);
 
 	/**
 	 * Get an {@link Integer} value from the meta-data.
@@ -49,7 +53,8 @@ public interface AutoConfigurationMetadata {
 	 * @param defaultValue the default value
 	 * @return the meta-data value or {@code defaultValue}
 	 */
-	Integer getInteger(String className, String key, Integer defaultValue);
+	@Contract("_, _, !null -> !null")
+	@Nullable Integer getInteger(String className, String key, @Nullable Integer defaultValue);
 
 	/**
 	 * Get a {@link Set} value from the meta-data.
@@ -57,7 +62,7 @@ public interface AutoConfigurationMetadata {
 	 * @param key the meta-data key
 	 * @return the meta-data value or {@code null}
 	 */
-	Set<String> getSet(String className, String key);
+	@Nullable Set<String> getSet(String className, String key);
 
 	/**
 	 * Get a {@link Set} value from the meta-data.
@@ -66,7 +71,8 @@ public interface AutoConfigurationMetadata {
 	 * @param defaultValue the default value
 	 * @return the meta-data value or {@code defaultValue}
 	 */
-	Set<String> getSet(String className, String key, Set<String> defaultValue);
+	@Contract("_, _, !null -> !null")
+	@Nullable Set<String> getSet(String className, String key, @Nullable Set<String> defaultValue);
 
 	/**
 	 * Get an {@link String} value from the meta-data.
@@ -74,7 +80,7 @@ public interface AutoConfigurationMetadata {
 	 * @param key the meta-data key
 	 * @return the meta-data value or {@code null}
 	 */
-	String get(String className, String key);
+	@Nullable String get(String className, String key);
 
 	/**
 	 * Get an {@link String} value from the meta-data.
@@ -83,6 +89,7 @@ public interface AutoConfigurationMetadata {
 	 * @param defaultValue the default value
 	 * @return the meta-data value or {@code defaultValue}
 	 */
-	String get(String className, String key, String defaultValue);
+	@Contract("_, _, !null -> !null")
+	@Nullable String get(String className, String key, @Nullable String defaultValue);
 
 }

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/AutoConfigurationMetadataLoader.java

@@ -22,6 +22,8 @@ import java.util.Enumeration;
 import java.util.Properties;
 import java.util.Set;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.core.io.UrlResource;
 import org.springframework.core.io.support.PropertiesLoaderUtils;
 import org.springframework.util.StringUtils;
@@ -42,7 +44,7 @@ final class AutoConfigurationMetadataLoader {
 		return loadMetadata(classLoader, PATH);
 	}
 
-	static AutoConfigurationMetadata loadMetadata(ClassLoader classLoader, String path) {
+	static AutoConfigurationMetadata loadMetadata(@Nullable ClassLoader classLoader, String path) {
 		try {
 			Enumeration<URL> urls = (classLoader != null) ? classLoader.getResources(path)
 					: ClassLoader.getSystemResources(path);
@@ -78,34 +80,34 @@ final class AutoConfigurationMetadataLoader {
 		}
 
 		@Override
-		public Integer getInteger(String className, String key) {
+		public @Nullable Integer getInteger(String className, String key) {
 			return getInteger(className, key, null);
 		}
 
 		@Override
-		public Integer getInteger(String className, String key, Integer defaultValue) {
+		public @Nullable Integer getInteger(String className, String key, @Nullable Integer defaultValue) {
 			String value = get(className, key);
 			return (value != null) ? Integer.valueOf(value) : defaultValue;
 		}
 
 		@Override
-		public Set<String> getSet(String className, String key) {
+		public @Nullable Set<String> getSet(String className, String key) {
 			return getSet(className, key, null);
 		}
 
 		@Override
-		public Set<String> getSet(String className, String key, Set<String> defaultValue) {
+		public @Nullable Set<String> getSet(String className, String key, @Nullable Set<String> defaultValue) {
 			String value = get(className, key);
 			return (value != null) ? StringUtils.commaDelimitedListToSet(value) : defaultValue;
 		}
 
 		@Override
-		public String get(String className, String key) {
+		public @Nullable String get(String className, String key) {
 			return get(className, key, null);
 		}
 
 		@Override
-		public String get(String className, String key, String defaultValue) {
+		public @Nullable String get(String className, String key, @Nullable String defaultValue) {
 			String value = this.properties.getProperty(className + "." + key);
 			return (value != null) ? value : defaultValue;
 		}

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/AutoConfigurationPackages.java

@@ -30,12 +30,14 @@ import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.NoSuchBeanDefinitionException;
 import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.beans.factory.config.ConstructorArgumentValues;
+import org.springframework.beans.factory.config.ConstructorArgumentValues.ValueHolder;
 import org.springframework.beans.factory.support.BeanDefinitionRegistry;
 import org.springframework.beans.factory.support.RootBeanDefinition;
 import org.springframework.boot.context.annotation.DeterminableImports;
 import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
 import org.springframework.core.annotation.AnnotationAttributes;
 import org.springframework.core.type.AnnotationMetadata;
+import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.StringUtils;
 
@@ -105,8 +107,9 @@ public abstract class AutoConfigurationPackages {
 	private static void addBasePackages(BeanDefinition beanDefinition, String[] additionalBasePackages) {
 		ConstructorArgumentValues constructorArgumentValues = beanDefinition.getConstructorArgumentValues();
 		if (constructorArgumentValues.hasIndexedArgumentValue(0)) {
-			String[] existingPackages = (String[]) constructorArgumentValues.getIndexedArgumentValue(0, String[].class)
-				.getValue();
+			ValueHolder indexedArgumentValue = constructorArgumentValues.getIndexedArgumentValue(0, String[].class);
+			Assert.state(indexedArgumentValue != null, "'indexedArgumentValue' must not be null");
+			String[] existingPackages = (String[]) indexedArgumentValue.getValue();
 			constructorArgumentValues.addIndexedArgumentValue(0,
 					Stream.concat(Stream.of(existingPackages), Stream.of(additionalBasePackages))
 						.distinct()
@@ -145,6 +148,7 @@ public abstract class AutoConfigurationPackages {
 		PackageImports(AnnotationMetadata metadata) {
 			AnnotationAttributes attributes = AnnotationAttributes
 				.fromMap(metadata.getAnnotationAttributes(AutoConfigurationPackage.class.getName(), false));
+			Assert.state(attributes != null, "'attributes' must not be null");
 			List<String> packageNames = new ArrayList<>(Arrays.asList(attributes.getStringArray("basePackages")));
 			for (Class<?> basePackageClass : attributes.getClassArray("basePackageClasses")) {
 				packageNames.add(basePackageClass.getPackage().getName());

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/AutoConfigurationReplacements.java

@@ -28,6 +28,8 @@ import java.util.Map;
 import java.util.Properties;
 import java.util.Set;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.context.annotation.ImportCandidates;
 import org.springframework.core.io.UrlResource;
 import org.springframework.util.Assert;
@@ -88,7 +90,7 @@ final class AutoConfigurationReplacements {
 	 * @param classLoader class loader to use for loading
 	 * @return list of names of annotated classes
 	 */
-	static AutoConfigurationReplacements load(Class<?> annotation, ClassLoader classLoader) {
+	static AutoConfigurationReplacements load(Class<?> annotation, @Nullable ClassLoader classLoader) {
 		Assert.notNull(annotation, "'annotation' must not be null");
 		ClassLoader classLoaderToUse = decideClassloader(classLoader);
 		String location = String.format(LOCATION, annotation.getName());
@@ -101,7 +103,7 @@ final class AutoConfigurationReplacements {
 		return new AutoConfigurationReplacements(replacements);
 	}
 
-	private static ClassLoader decideClassloader(ClassLoader classLoader) {
+	private static ClassLoader decideClassloader(@Nullable ClassLoader classLoader) {
 		if (classLoader == null) {
 			return ImportCandidates.class.getClassLoader();
 		}

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/AutoConfigurationSorter.java

@@ -30,6 +30,8 @@ import java.util.Set;
 import java.util.TreeSet;
 import java.util.function.UnaryOperator;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.core.type.AnnotationMetadata;
 import org.springframework.core.type.classreading.MetadataReader;
 import org.springframework.core.type.classreading.MetadataReaderFactory;
@@ -47,12 +49,13 @@ class AutoConfigurationSorter {
 
 	private final MetadataReaderFactory metadataReaderFactory;
 
-	private final AutoConfigurationMetadata autoConfigurationMetadata;
+	private final @Nullable AutoConfigurationMetadata autoConfigurationMetadata;
 
-	private final UnaryOperator<String> replacementMapper;
+	private final @Nullable UnaryOperator<String> replacementMapper;
 
 	AutoConfigurationSorter(MetadataReaderFactory metadataReaderFactory,
-			AutoConfigurationMetadata autoConfigurationMetadata, UnaryOperator<String> replacementMapper) {
+			@Nullable AutoConfigurationMetadata autoConfigurationMetadata,
+			@Nullable UnaryOperator<String> replacementMapper) {
 		Assert.notNull(metadataReaderFactory, "'metadataReaderFactory' must not be null");
 		this.metadataReaderFactory = metadataReaderFactory;
 		this.autoConfigurationMetadata = autoConfigurationMetadata;
@@ -91,7 +94,7 @@ class AutoConfigurationSorter {
 	}
 
 	private void doSortByAfterAnnotation(AutoConfigurationClasses classes, List<String> toSort, Set<String> sorted,
-			Set<String> processing, String current) {
+			Set<String> processing, @Nullable String current) {
 		if (current == null) {
 			current = toSort.remove(0);
 		}
@@ -118,7 +121,7 @@ class AutoConfigurationSorter {
 		private final Map<String, AutoConfigurationClass> classes = new LinkedHashMap<>();
 
 		AutoConfigurationClasses(MetadataReaderFactory metadataReaderFactory,
-				AutoConfigurationMetadata autoConfigurationMetadata, Collection<String> classNames) {
+				@Nullable AutoConfigurationMetadata autoConfigurationMetadata, Collection<String> classNames) {
 			addToClasses(metadataReaderFactory, autoConfigurationMetadata, classNames, true);
 		}
 
@@ -127,7 +130,8 @@ class AutoConfigurationSorter {
 		}
 
 		private void addToClasses(MetadataReaderFactory metadataReaderFactory,
-				AutoConfigurationMetadata autoConfigurationMetadata, Collection<String> classNames, boolean required) {
+				@Nullable AutoConfigurationMetadata autoConfigurationMetadata, Collection<String> classNames,
+				boolean required) {
 			for (String className : classNames) {
 				if (!this.classes.containsKey(className)) {
 					AutoConfigurationClass autoConfigurationClass = new AutoConfigurationClass(className,
@@ -147,7 +151,9 @@ class AutoConfigurationSorter {
 		}
 
 		AutoConfigurationClass get(String className) {
-			return this.classes.get(className);
+			AutoConfigurationClass autoConfigurationClass = this.classes.get(className);
+			Assert.state(autoConfigurationClass != null, "'autoConfigurationClass' must not be null");
+			return autoConfigurationClass;
 		}
 
 		Set<String> getClassesRequestedAfter(String className) {
@@ -168,16 +174,16 @@ class AutoConfigurationSorter {
 
 		private final MetadataReaderFactory metadataReaderFactory;
 
-		private final AutoConfigurationMetadata autoConfigurationMetadata;
+		private final @Nullable AutoConfigurationMetadata autoConfigurationMetadata;
 
-		private volatile AnnotationMetadata annotationMetadata;
+		private volatile @Nullable AnnotationMetadata annotationMetadata;
 
-		private volatile Set<String> before;
+		private volatile @Nullable Set<String> before;
 
-		private volatile Set<String> after;
+		private volatile @Nullable Set<String> after;
 
 		AutoConfigurationClass(String className, MetadataReaderFactory metadataReaderFactory,
-				AutoConfigurationMetadata autoConfigurationMetadata) {
+				@Nullable AutoConfigurationMetadata autoConfigurationMetadata) {
 			this.className = className;
 			this.metadataReaderFactory = metadataReaderFactory;
 			this.autoConfigurationMetadata = autoConfigurationMetadata;
@@ -210,12 +216,15 @@ class AutoConfigurationSorter {
 		}
 
 		private Set<String> getClassNames(String metadataKey, Class<? extends Annotation> annotation) {
-			Set<String> annotationValue = wasProcessed()
-					? this.autoConfigurationMetadata.getSet(this.className, metadataKey, Collections.emptySet())
-					: getAnnotationValue(annotation);
+			Set<String> annotationValue = wasProcessed() ? getSet(metadataKey) : getAnnotationValue(annotation);
 			return applyReplacements(annotationValue);
 		}
 
+		private Set<String> getSet(String metadataKey) {
+			Assert.state(this.autoConfigurationMetadata != null, "'autoConfigurationMetadata' must not be null");
+			return this.autoConfigurationMetadata.getSet(this.className, metadataKey, Collections.emptySet());
+		}
+
 		private Set<String> applyReplacements(Set<String> values) {
 			if (AutoConfigurationSorter.this.replacementMapper == null) {
 				return values;
@@ -229,10 +238,11 @@ class AutoConfigurationSorter {
 
 		private int getOrder() {
 			if (wasProcessed()) {
+				Assert.state(this.autoConfigurationMetadata != null, "'autoConfigurationMetadata' must not be null");
 				return this.autoConfigurationMetadata.getInteger(this.className, "AutoConfigureOrder",
 						AutoConfigureOrder.DEFAULT_ORDER);
 			}
-			Map<String, Object> attributes = getAnnotationMetadata()
+			Map<String, @Nullable Object> attributes = getAnnotationMetadata()
 				.getAnnotationAttributes(AutoConfigureOrder.class.getName());
 			return (attributes != null) ? (Integer) attributes.get("value") : AutoConfigureOrder.DEFAULT_ORDER;
 		}
@@ -243,8 +253,8 @@ class AutoConfigurationSorter {
 		}
 
 		private Set<String> getAnnotationValue(Class<?> annotation) {
-			Map<String, Object> attributes = getAnnotationMetadata().getAnnotationAttributes(annotation.getName(),
-					true);
+			Map<String, @Nullable Object> attributes = getAnnotationMetadata()
+				.getAnnotationAttributes(annotation.getName(), true);
 			if (attributes == null) {
 				return Collections.emptySet();
 			}

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/ImportAutoConfigurationImportSelector.java

@@ -28,6 +28,8 @@ import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.context.annotation.DeterminableImports;
 import org.springframework.boot.context.annotation.ImportCandidates;
 import org.springframework.core.annotation.AnnotatedElementUtils;
@@ -71,12 +73,13 @@ class ImportAutoConfigurationImportSelector extends AutoConfigurationImportSelec
 	}
 
 	@Override
-	protected AnnotationAttributes getAttributes(AnnotationMetadata metadata) {
+	protected @Nullable AnnotationAttributes getAttributes(AnnotationMetadata metadata) {
 		return null;
 	}
 
 	@Override
-	protected List<String> getCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes) {
+	protected List<String> getCandidateConfigurations(AnnotationMetadata metadata,
+			@Nullable AnnotationAttributes attributes) {
 		List<String> candidates = new ArrayList<>();
 		Map<Class<?>, List<Annotation>> annotations = getAnnotations(metadata);
 		annotations.forEach(
@@ -93,13 +96,13 @@ class ImportAutoConfigurationImportSelector extends AutoConfigurationImportSelec
 
 	private Collection<String> getConfigurationsForAnnotation(Class<?> source, Annotation annotation) {
 		String[] classes = (String[]) AnnotationUtils.getAnnotationAttributes(annotation, true).get("classes");
-		if (classes.length > 0) {
+		if (classes != null && classes.length > 0) {
 			return Arrays.asList(classes);
 		}
 		return loadFactoryNames(source).stream().map(this::mapFactoryName).filter(Objects::nonNull).toList();
 	}
 
-	private String mapFactoryName(String name) {
+	private @Nullable String mapFactoryName(String name) {
 		if (!name.startsWith(OPTIONAL_PREFIX)) {
 			return name;
 		}
@@ -117,7 +120,7 @@ class ImportAutoConfigurationImportSelector extends AutoConfigurationImportSelec
 	}
 
 	@Override
-	protected Set<String> getExclusions(AnnotationMetadata metadata, AnnotationAttributes attributes) {
+	protected Set<String> getExclusions(AnnotationMetadata metadata, @Nullable AnnotationAttributes attributes) {
 		Set<String> exclusions = new LinkedHashSet<>();
 		Class<?> source = ClassUtils.resolveClassName(metadata.getClassName(), getBeanClassLoader());
 		for (String annotationName : ANNOTATION_NAMES) {
@@ -148,7 +151,7 @@ class ImportAutoConfigurationImportSelector extends AutoConfigurationImportSelec
 		return Collections.unmodifiableMap(annotations);
 	}
 
-	private void collectAnnotations(Class<?> source, MultiValueMap<Class<?>, Annotation> annotations,
+	private void collectAnnotations(@Nullable Class<?> source, MultiValueMap<Class<?>, Annotation> annotations,
 			HashSet<Class<?>> seen) {
 		if (source != null && seen.add(source)) {
 			for (Annotation annotation : source.getDeclaredAnnotations()) {

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/SharedMetadataReaderFactoryContextInitializer.java

@@ -191,6 +191,7 @@ class SharedMetadataReaderFactoryContextInitializer implements
 			implements FactoryBean<ConcurrentReferenceCachingMetadataReaderFactory>, ResourceLoaderAware,
 			ApplicationListener<ContextRefreshedEvent> {
 
+		@SuppressWarnings("NullAway.Init")
 		private ConcurrentReferenceCachingMetadataReaderFactory metadataReaderFactory;
 
 		@Override

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/admin/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Auto-configuration for admin-related features.
  */
+@NullMarked
 package org.springframework.boot.autoconfigure.admin;
+
+import org.jspecify.annotations.NullMarked;

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/aop/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Auto-configuration for Spring AOP.
  */
+@NullMarked
 package org.springframework.boot.autoconfigure.aop;
+
+import org.jspecify.annotations.NullMarked;

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/availability/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Auto-configuration for application availability features.
  */
+@NullMarked
 package org.springframework.boot.autoconfigure.availability;
+
+import org.jspecify.annotations.NullMarked;

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/cache/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Auto-configuration base classes for Caching support.
  */
+@NullMarked
 package org.springframework.boot.autoconfigure.cache;
+
+import org.jspecify.annotations.NullMarked;

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/AbstractNestedCondition.java

@@ -22,6 +22,8 @@ import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.beans.BeanUtils;
 import org.springframework.context.annotation.Condition;
 import org.springframework.context.annotation.ConditionContext;
@@ -153,8 +155,8 @@ public abstract class AbstractNestedCondition extends SpringBootCondition implem
 
 		@SuppressWarnings("unchecked")
 		private List<String[]> getConditionClasses(AnnotatedTypeMetadata metadata) {
-			MultiValueMap<String, Object> attributes = metadata.getAllAnnotationAttributes(Conditional.class.getName(),
-					true);
+			MultiValueMap<String, @Nullable Object> attributes = metadata
+				.getAllAnnotationAttributes(Conditional.class.getName(), true);
 			Object values = (attributes != null) ? attributes.get("value") : null;
 			return (List<String[]>) ((values != null) ? values : Collections.emptyList());
 		}

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/ConditionEvaluationReport.java

@@ -30,6 +30,8 @@ import java.util.TreeMap;
 import java.util.stream.Stream;
 import java.util.stream.StreamSupport;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
 import org.springframework.context.annotation.Condition;
@@ -58,7 +60,7 @@ public final class ConditionEvaluationReport {
 
 	private boolean addedAncestorOutcomes;
 
-	private ConditionEvaluationReport parent;
+	private @Nullable ConditionEvaluationReport parent;
 
 	private final List<String> exclusions = new ArrayList<>();
 
@@ -154,7 +156,7 @@ public final class ConditionEvaluationReport {
 	 * The parent report (from a parent BeanFactory if there is one).
 	 * @return the parent report (or null if there isn't one)
 	 */
-	public ConditionEvaluationReport getParent() {
+	public @Nullable ConditionEvaluationReport getParent() {
 		return this.parent;
 	}
 
@@ -164,7 +166,7 @@ public final class ConditionEvaluationReport {
 	 * @param beanFactory the bean factory (may be {@code null})
 	 * @return the {@link ConditionEvaluationReport} or {@code null}
 	 */
-	public static ConditionEvaluationReport find(BeanFactory beanFactory) {
+	public static @Nullable ConditionEvaluationReport find(BeanFactory beanFactory) {
 		if (beanFactory instanceof ConfigurableListableBeanFactory) {
 			return ConditionEvaluationReport.get((ConfigurableListableBeanFactory) beanFactory);
 		}
@@ -191,7 +193,7 @@ public final class ConditionEvaluationReport {
 		}
 	}
 
-	private static void locateParent(BeanFactory beanFactory, ConditionEvaluationReport report) {
+	private static void locateParent(@Nullable BeanFactory beanFactory, ConditionEvaluationReport report) {
 		if (beanFactory != null && report.parent == null && beanFactory.containsBean(BEAN_NAME)) {
 			report.parent = beanFactory.getBean(BEAN_NAME, ConditionEvaluationReport.class);
 		}

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/ConditionEvaluationReportAutoConfigurationImportListener.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.autoconfigure.condition;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.BeanFactoryAware;
@@ -32,7 +34,7 @@ import org.springframework.boot.autoconfigure.AutoConfigurationImportListener;
 class ConditionEvaluationReportAutoConfigurationImportListener
 		implements AutoConfigurationImportListener, BeanFactoryAware {
 
-	private ConfigurableListableBeanFactory beanFactory;
+	private @Nullable ConfigurableListableBeanFactory beanFactory;
 
 	@Override
 	public void onAutoConfigurationImportEvent(AutoConfigurationImportEvent event) {

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/ConditionMessage.java

@@ -23,6 +23,8 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.CollectionUtils;
@@ -38,13 +40,13 @@ import org.springframework.util.StringUtils;
  */
 public final class ConditionMessage {
 
-	private final String message;
+	private final @Nullable String message;
 
 	private ConditionMessage() {
 		this(null);
 	}
 
-	private ConditionMessage(String message) {
+	private ConditionMessage(@Nullable String message) {
 		this.message = message;
 	}
 
@@ -87,7 +89,7 @@ public final class ConditionMessage {
 	 * @param message the message to append
 	 * @return a new {@link ConditionMessage} instance
 	 */
-	public ConditionMessage append(String message) {
+	public ConditionMessage append(@Nullable String message) {
 		if (!StringUtils.hasLength(message)) {
 			return this;
 		}
@@ -158,7 +160,7 @@ public final class ConditionMessage {
 	 * @param messages the source messages (may be {@code null})
 	 * @return a new {@link ConditionMessage} instance
 	 */
-	public static ConditionMessage of(Collection<? extends ConditionMessage> messages) {
+	public static ConditionMessage of(@Nullable Collection<? extends ConditionMessage> messages) {
 		ConditionMessage result = new ConditionMessage();
 		if (messages != null) {
 			for (ConditionMessage message : messages) {
@@ -296,7 +298,7 @@ public final class ConditionMessage {
 		 * @param reason the reason for the message
 		 * @return a built {@link ConditionMessage}
 		 */
-		public ConditionMessage because(String reason) {
+		public ConditionMessage because(@Nullable String reason) {
 			if (StringUtils.hasLength(reason)) {
 				return new ConditionMessage(ConditionMessage.this,
 						StringUtils.hasLength(this.condition) ? this.condition + " " + reason : reason);
@@ -343,7 +345,7 @@ public final class ConditionMessage {
 		 * @param items the items (may be {@code null})
 		 * @return a built {@link ConditionMessage}
 		 */
-		public ConditionMessage items(Object... items) {
+		public ConditionMessage items(Object @Nullable ... items) {
 			return items(Style.NORMAL, items);
 		}
 
@@ -355,7 +357,7 @@ public final class ConditionMessage {
 		 * @param items the items (may be {@code null})
 		 * @return a built {@link ConditionMessage}
 		 */
-		public ConditionMessage items(Style style, Object... items) {
+		public ConditionMessage items(Style style, Object @Nullable ... items) {
 			return items(style, (items != null) ? Arrays.asList(items) : null);
 		}
 
@@ -366,7 +368,7 @@ public final class ConditionMessage {
 		 * @param items the source of the items (may be {@code null})
 		 * @return a built {@link ConditionMessage}
 		 */
-		public ConditionMessage items(Collection<?> items) {
+		public ConditionMessage items(@Nullable Collection<?> items) {
 			return items(Style.NORMAL, items);
 		}
 
@@ -378,7 +380,7 @@ public final class ConditionMessage {
 		 * @param items the source of the items (may be {@code null})
 		 * @return a built {@link ConditionMessage}
 		 */
-		public ConditionMessage items(Style style, Collection<?> items) {
+		public ConditionMessage items(Style style, @Nullable Collection<?> items) {
 			Assert.notNull(style, "'style' must not be null");
 			StringBuilder message = new StringBuilder(this.reason);
 			items = style.applyTo(items);
@@ -408,7 +410,7 @@ public final class ConditionMessage {
 		NORMAL {
 
 			@Override
-			protected Object applyToItem(Object item) {
+			protected @Nullable Object applyToItem(@Nullable Object item) {
 				return item;
 			}
 
@@ -420,24 +422,27 @@ public final class ConditionMessage {
 		QUOTE {
 
 			@Override
-			protected String applyToItem(Object item) {
+			protected @Nullable String applyToItem(@Nullable Object item) {
 				return (item != null) ? "'" + item + "'" : null;
 			}
 
 		};
 
-		public Collection<?> applyTo(Collection<?> items) {
+		public @Nullable Collection<?> applyTo(@Nullable Collection<?> items) {
 			if (items == null) {
 				return null;
 			}
 			List<Object> result = new ArrayList<>(items.size());
 			for (Object item : items) {
-				result.add(applyToItem(item));
+				Object applied = applyToItem(item);
+				if (applied != null) {
+					result.add(applied);
+				}
 			}
 			return result;
 		}
 
-		protected abstract Object applyToItem(Object item);
+		protected abstract @Nullable Object applyToItem(@Nullable Object item);
 
 	}
 

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/ConditionOutcome.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.autoconfigure.condition;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 
@@ -111,13 +113,13 @@ public class ConditionOutcome {
 	 * Return an outcome message or {@code null}.
 	 * @return the message or {@code null}
 	 */
-	public String getMessage() {
+	public @Nullable String getMessage() {
 		return this.message.isEmpty() ? null : this.message.toString();
 	}
 
 	/**
-	 * Return an outcome message or {@code null}.
-	 * @return the message or {@code null}
+	 * Return an outcome message.
+	 * @return the message
 	 */
 	public ConditionMessage getConditionMessage() {
 		return this.message;

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/FilteringSpringBootCondition.java

@@ -21,12 +21,15 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.BeanClassLoaderAware;
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.BeanFactoryAware;
 import org.springframework.boot.autoconfigure.AutoConfigurationImportFilter;
 import org.springframework.boot.autoconfigure.AutoConfigurationMetadata;
+import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.CollectionUtils;
 
@@ -39,28 +42,33 @@ import org.springframework.util.CollectionUtils;
 abstract class FilteringSpringBootCondition extends SpringBootCondition
 		implements AutoConfigurationImportFilter, BeanFactoryAware, BeanClassLoaderAware {
 
+	@SuppressWarnings("NullAway.Init")
 	private BeanFactory beanFactory;
 
+	@SuppressWarnings("NullAway.Init")
 	private ClassLoader beanClassLoader;
 
 	@Override
-	public boolean[] match(String[] autoConfigurationClasses, AutoConfigurationMetadata autoConfigurationMetadata) {
+	public boolean[] match(@Nullable String[] autoConfigurationClasses,
+			AutoConfigurationMetadata autoConfigurationMetadata) {
 		ConditionEvaluationReport report = ConditionEvaluationReport.find(this.beanFactory);
-		ConditionOutcome[] outcomes = getOutcomes(autoConfigurationClasses, autoConfigurationMetadata);
+		@Nullable ConditionOutcome[] outcomes = getOutcomes(autoConfigurationClasses, autoConfigurationMetadata);
 		boolean[] match = new boolean[outcomes.length];
 		for (int i = 0; i < outcomes.length; i++) {
 			match[i] = (outcomes[i] == null || outcomes[i].isMatch());
 			if (!match[i] && outcomes[i] != null) {
-				logOutcome(autoConfigurationClasses[i], outcomes[i]);
+				String autoConfigurationClass = autoConfigurationClasses[i];
+				Assert.state(autoConfigurationClass != null, "'autoConfigurationClass' must not be null");
+				logOutcome(autoConfigurationClass, outcomes[i]);
 				if (report != null) {
-					report.recordConditionEvaluation(autoConfigurationClasses[i], this, outcomes[i]);
+					report.recordConditionEvaluation(autoConfigurationClass, this, outcomes[i]);
 				}
 			}
 		}
 		return match;
 	}
 
-	protected abstract ConditionOutcome[] getOutcomes(String[] autoConfigurationClasses,
+	protected abstract @Nullable ConditionOutcome[] getOutcomes(@Nullable String[] autoConfigurationClasses,
 			AutoConfigurationMetadata autoConfigurationMetadata);
 
 	@Override
@@ -81,8 +89,8 @@ abstract class FilteringSpringBootCondition extends SpringBootCondition
 		this.beanClassLoader = classLoader;
 	}
 
-	protected final List<String> filter(Collection<String> classNames, ClassNameFilter classNameFilter,
-			ClassLoader classLoader) {
+	protected final List<String> filter(@Nullable Collection<String> classNames, ClassNameFilter classNameFilter,
+			@Nullable ClassLoader classLoader) {
 		if (CollectionUtils.isEmpty(classNames)) {
 			return Collections.emptyList();
 		}
@@ -103,7 +111,8 @@ abstract class FilteringSpringBootCondition extends SpringBootCondition
 	 * @return a resolved class
 	 * @throws ClassNotFoundException if the class cannot be found
 	 */
-	protected static Class<?> resolve(String className, ClassLoader classLoader) throws ClassNotFoundException {
+	protected static Class<?> resolve(String className, @Nullable ClassLoader classLoader)
+			throws ClassNotFoundException {
 		if (classLoader != null) {
 			return Class.forName(className, false, classLoader);
 		}
@@ -115,7 +124,7 @@ abstract class FilteringSpringBootCondition extends SpringBootCondition
 		PRESENT {
 
 			@Override
-			public boolean matches(String className, ClassLoader classLoader) {
+			public boolean matches(String className, @Nullable ClassLoader classLoader) {
 				return isPresent(className, classLoader);
 			}
 
@@ -124,15 +133,15 @@ abstract class FilteringSpringBootCondition extends SpringBootCondition
 		MISSING {
 
 			@Override
-			public boolean matches(String className, ClassLoader classLoader) {
+			public boolean matches(String className, @Nullable ClassLoader classLoader) {
 				return !isPresent(className, classLoader);
 			}
 
 		};
 
-		abstract boolean matches(String className, ClassLoader classLoader);
+		abstract boolean matches(String className, @Nullable ClassLoader classLoader);
 
-		private static boolean isPresent(String className, ClassLoader classLoader) {
+		private static boolean isPresent(String className, @Nullable ClassLoader classLoader) {
 			if (classLoader == null) {
 				classLoader = ClassUtils.getDefaultClassLoader();
 			}

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/OnBeanCondition.java

@@ -34,6 +34,8 @@ import java.util.Set;
 import java.util.function.BiPredicate;
 import java.util.function.Predicate;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.aop.scope.ScopedProxyUtils;
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.BeanFactoryUtils;
@@ -60,6 +62,7 @@ import org.springframework.core.annotation.MergedAnnotations;
 import org.springframework.core.annotation.Order;
 import org.springframework.core.type.AnnotatedTypeMetadata;
 import org.springframework.core.type.MethodMetadata;
+import org.springframework.lang.Contract;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.CollectionUtils;
@@ -90,9 +93,9 @@ class OnBeanCondition extends FilteringSpringBootCondition implements Configurat
 	}
 
 	@Override
-	protected final ConditionOutcome[] getOutcomes(String[] autoConfigurationClasses,
+	protected final @Nullable ConditionOutcome[] getOutcomes(@Nullable String[] autoConfigurationClasses,
 			AutoConfigurationMetadata autoConfigurationMetadata) {
-		ConditionOutcome[] outcomes = new ConditionOutcome[autoConfigurationClasses.length];
+		@Nullable ConditionOutcome[] outcomes = new ConditionOutcome[autoConfigurationClasses.length];
 		for (int i = 0; i < outcomes.length; i++) {
 			String autoConfigurationClass = autoConfigurationClasses[i];
 			if (autoConfigurationClass != null) {
@@ -108,7 +111,8 @@ class OnBeanCondition extends FilteringSpringBootCondition implements Configurat
 		return outcomes;
 	}
 
-	private ConditionOutcome getOutcome(Set<String> requiredBeanTypes, Class<? extends Annotation> annotation) {
+	private @Nullable ConditionOutcome getOutcome(@Nullable Set<String> requiredBeanTypes,
+			Class<? extends Annotation> annotation) {
 		List<String> missing = filter(requiredBeanTypes, ClassNameFilter.MISSING, getBeanClassLoader());
 		if (!missing.isEmpty()) {
 			ConditionMessage message = ConditionMessage.forCondition(annotation)
@@ -171,7 +175,9 @@ class OnBeanCondition extends FilteringSpringBootCondition implements Configurat
 			return ConditionOutcome
 				.match(spec.message(matchMessage).found("a single bean").items(Style.QUOTE, allBeans));
 		}
-		Map<String, BeanDefinition> beanDefinitions = getBeanDefinitions(spec.context.getBeanFactory(), allBeans,
+		ConfigurableListableBeanFactory beanFactory = spec.context.getBeanFactory();
+		Assert.state(beanFactory != null, "'beanFactory' must not be null");
+		Map<String, BeanDefinition> beanDefinitions = getBeanDefinitions(beanFactory, allBeans,
 				spec.getStrategy() == SearchStrategy.ALL);
 		List<String> primaryBeans = getPrimaryBeans(beanDefinitions);
 		if (primaryBeans.size() == 1) {
@@ -249,6 +255,7 @@ class OnBeanCondition extends FilteringSpringBootCondition implements Configurat
 
 	private ConfigurableListableBeanFactory getSearchBeanFactory(Spec<?> spec) {
 		ConfigurableListableBeanFactory beanFactory = spec.getContext().getBeanFactory();
+		Assert.state(beanFactory != null, "'beanFactory' must not be null'");
 		if (spec.getStrategy() == SearchStrategy.ANCESTORS) {
 			BeanFactory parent = beanFactory.getParentBeanFactory();
 			Assert.state(parent instanceof ConfigurableListableBeanFactory,
@@ -269,8 +276,8 @@ class OnBeanCondition extends FilteringSpringBootCondition implements Configurat
 		return matchedNames;
 	}
 
-	private boolean isCandidate(ConfigurableListableBeanFactory beanFactory, String name, BeanDefinition definition,
-			Set<String> ignoredBeans) {
+	private boolean isCandidate(ConfigurableListableBeanFactory beanFactory, String name,
+			@Nullable BeanDefinition definition, Set<String> ignoredBeans) {
 		return (!ignoredBeans.contains(name)) && (definition == null
 				|| isAutowireCandidate(beanFactory, name, definition) && isDefaultCandidate(definition));
 	}
@@ -316,12 +323,14 @@ class OnBeanCondition extends FilteringSpringBootCondition implements Configurat
 		return (result != null) ? result : Collections.emptyMap();
 	}
 
-	private Map<String, BeanDefinition> collectBeanDefinitionsForType(ListableBeanFactory beanFactory,
+	private @Nullable Map<String, BeanDefinition> collectBeanDefinitionsForType(ListableBeanFactory beanFactory,
 			boolean considerHierarchy, ResolvableType type, Set<ResolvableType> parameterizedContainers,
-			Map<String, BeanDefinition> result) {
+			@Nullable Map<String, BeanDefinition> result) {
 		result = putAll(result, beanFactory.getBeanNamesForType(type, true, false), beanFactory);
 		for (ResolvableType parameterizedContainer : parameterizedContainers) {
-			ResolvableType generic = ResolvableType.forClassWithGenerics(parameterizedContainer.resolve(), type);
+			Class<?> resolved = parameterizedContainer.resolve();
+			Assert.state(resolved != null, "'resolved' must not be null");
+			ResolvableType generic = ResolvableType.forClassWithGenerics(resolved, type);
 			result = putAll(result, beanFactory.getBeanNamesForType(generic, true, false), beanFactory);
 		}
 		if (considerHierarchy && beanFactory instanceof HierarchicalBeanFactory hierarchicalBeanFactory) {
@@ -334,7 +343,7 @@ class OnBeanCondition extends FilteringSpringBootCondition implements Configurat
 		return result;
 	}
 
-	private Map<String, BeanDefinition> getBeanDefinitionsForAnnotation(ClassLoader classLoader,
+	private Map<String, BeanDefinition> getBeanDefinitionsForAnnotation(@Nullable ClassLoader classLoader,
 			ConfigurableListableBeanFactory beanFactory, String type, boolean considerHierarchy) throws LinkageError {
 		Map<String, BeanDefinition> result = null;
 		try {
@@ -348,13 +357,14 @@ class OnBeanCondition extends FilteringSpringBootCondition implements Configurat
 	}
 
 	@SuppressWarnings("unchecked")
-	private Class<? extends Annotation> resolveAnnotationType(ClassLoader classLoader, String type)
+	private Class<? extends Annotation> resolveAnnotationType(@Nullable ClassLoader classLoader, String type)
 			throws ClassNotFoundException {
 		return (Class<? extends Annotation>) resolve(type, classLoader);
 	}
 
-	private Map<String, BeanDefinition> collectBeanDefinitionsForAnnotation(ListableBeanFactory beanFactory,
-			Class<? extends Annotation> annotationType, boolean considerHierarchy, Map<String, BeanDefinition> result) {
+	private @Nullable Map<String, BeanDefinition> collectBeanDefinitionsForAnnotation(ListableBeanFactory beanFactory,
+			Class<? extends Annotation> annotationType, boolean considerHierarchy,
+			@Nullable Map<String, BeanDefinition> result) {
 		result = putAll(result, getBeanNamesForAnnotation(beanFactory, annotationType), beanFactory);
 		if (considerHierarchy) {
 			BeanFactory parent = ((HierarchicalBeanFactory) beanFactory).getParentBeanFactory();
@@ -477,7 +487,7 @@ class OnBeanCondition extends FilteringSpringBootCondition implements Configurat
 		return matches;
 	}
 
-	private BeanDefinition findBeanDefinition(ConfigurableListableBeanFactory beanFactory, String beanName,
+	private @Nullable BeanDefinition findBeanDefinition(ConfigurableListableBeanFactory beanFactory, String beanName,
 			boolean considerHierarchy) {
 		if (beanFactory.containsBeanDefinition(beanName)) {
 			return beanFactory.getBeanDefinition(beanName);
@@ -489,7 +499,7 @@ class OnBeanCondition extends FilteringSpringBootCondition implements Configurat
 		return null;
 	}
 
-	private static Set<String> addAll(Set<String> result, Collection<String> additional) {
+	private static @Nullable Set<String> addAll(@Nullable Set<String> result, @Nullable Collection<String> additional) {
 		if (CollectionUtils.isEmpty(additional)) {
 			return result;
 		}
@@ -498,8 +508,8 @@ class OnBeanCondition extends FilteringSpringBootCondition implements Configurat
 		return result;
 	}
 
-	private static Map<String, BeanDefinition> putAll(Map<String, BeanDefinition> result, String[] beanNames,
-			ListableBeanFactory beanFactory) {
+	private static @Nullable Map<String, BeanDefinition> putAll(@Nullable Map<String, BeanDefinition> result,
+			String[] beanNames, ListableBeanFactory beanFactory) {
 		if (ObjectUtils.isEmpty(beanNames)) {
 			return result;
 		}
@@ -517,7 +527,8 @@ class OnBeanCondition extends FilteringSpringBootCondition implements Configurat
 		return result;
 	}
 
-	private static BeanDefinition getBeanDefinition(String beanName, ConfigurableListableBeanFactory beanFactory) {
+	private static @Nullable BeanDefinition getBeanDefinition(String beanName,
+			ConfigurableListableBeanFactory beanFactory) {
 		try {
 			return beanFactory.getBeanDefinition(beanName);
 		}
@@ -548,7 +559,7 @@ class OnBeanCondition extends FilteringSpringBootCondition implements Configurat
 
 		private final Set<ResolvableType> parameterizedContainers;
 
-		private final SearchStrategy strategy;
+		private final @Nullable SearchStrategy strategy;
 
 		Spec(ConditionContext context, AnnotatedTypeMetadata metadata, MergedAnnotations annotations,
 				Class<A> annotationType) {
@@ -621,7 +632,7 @@ class OnBeanCondition extends FilteringSpringBootCondition implements Configurat
 			return resolved;
 		}
 
-		protected void validate(BeanTypeDeductionException ex) {
+		protected void validate(@Nullable BeanTypeDeductionException ex) {
 			if (!hasAtLeastOneElement(getTypes(), getNames(), getAnnotations())) {
 				String message = getAnnotationName() + " did not specify a bean using type, name or annotation";
 				if (ex == null) {
@@ -671,13 +682,13 @@ class OnBeanCondition extends FilteringSpringBootCondition implements Configurat
 			return returnType;
 		}
 
-		private boolean isParameterizedContainer(Class<?> type) {
+		private boolean isParameterizedContainer(@Nullable Class<?> type) {
 			return (type != null) && this.parameterizedContainers.stream()
 				.map(ResolvableType::resolve)
 				.anyMatch((container) -> container != null && container.isAssignableFrom(type));
 		}
 
-		private ResolvableType getMethodReturnType(MethodMetadata metadata, ClassLoader classLoader)
+		private ResolvableType getMethodReturnType(MethodMetadata metadata, @Nullable ClassLoader classLoader)
 				throws ClassNotFoundException, LinkageError {
 			Class<?> declaringClass = resolve(metadata.getDeclaringClassName(), classLoader);
 			Method beanMethod = findBeanMethod(declaringClass, metadata.getMethodName());
@@ -698,7 +709,8 @@ class OnBeanCondition extends FilteringSpringBootCondition implements Configurat
 			throw new IllegalStateException("Unable to find bean method " + methodName);
 		}
 
-		private boolean isBeanMethod(Method method) {
+		@Contract("null -> false")
+		private boolean isBeanMethod(@Nullable Method method) {
 			return method != null && MergedAnnotations.from(method, MergedAnnotations.SearchStrategy.TYPE_HIERARCHY)
 				.isPresent(Bean.class);
 		}
@@ -761,8 +773,10 @@ class OnBeanCondition extends FilteringSpringBootCondition implements Configurat
 				string.append(StringUtils.collectionToCommaDelimitedString(this.ignoredTypes));
 				string.append("; ");
 			}
-			string.append("SearchStrategy: ");
-			string.append(this.strategy.toString().toLowerCase(Locale.ENGLISH));
+			if (this.strategy != null) {
+				string.append("SearchStrategy: ");
+				string.append(this.strategy.toString().toLowerCase(Locale.ENGLISH));
+			}
 			string.append(")");
 			return string.toString();
 		}
@@ -789,7 +803,7 @@ class OnBeanCondition extends FilteringSpringBootCondition implements Configurat
 		}
 
 		@Override
-		protected void validate(BeanTypeDeductionException ex) {
+		protected void validate(@Nullable BeanTypeDeductionException ex) {
 			Assert.isTrue(getTypes().size() == 1,
 					() -> getAnnotationName() + " annotations must specify only one type (got "
 							+ StringUtils.collectionToCommaDelimitedString(getTypes()) + ")");

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/OnClassCondition.java

@@ -20,6 +20,8 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.autoconfigure.AutoConfigurationImportFilter;
 import org.springframework.boot.autoconfigure.AutoConfigurationMetadata;
 import org.springframework.boot.autoconfigure.condition.ConditionMessage.Style;
@@ -44,7 +46,7 @@ import org.springframework.util.StringUtils;
 class OnClassCondition extends FilteringSpringBootCondition {
 
 	@Override
-	protected final ConditionOutcome[] getOutcomes(String[] autoConfigurationClasses,
+	protected final @Nullable ConditionOutcome[] getOutcomes(@Nullable String[] autoConfigurationClasses,
 			AutoConfigurationMetadata autoConfigurationMetadata) {
 		// Split the work and perform half in a background thread if more than one
 		// processor is available. Using a single additional thread seems to offer the
@@ -59,22 +61,22 @@ class OnClassCondition extends FilteringSpringBootCondition {
 		}
 	}
 
-	private ConditionOutcome[] resolveOutcomesThreaded(String[] autoConfigurationClasses,
+	private @Nullable ConditionOutcome[] resolveOutcomesThreaded(@Nullable String[] autoConfigurationClasses,
 			AutoConfigurationMetadata autoConfigurationMetadata) {
 		int split = autoConfigurationClasses.length / 2;
 		OutcomesResolver firstHalfResolver = createOutcomesResolver(autoConfigurationClasses, 0, split,
 				autoConfigurationMetadata);
 		OutcomesResolver secondHalfResolver = new StandardOutcomesResolver(autoConfigurationClasses, split,
 				autoConfigurationClasses.length, autoConfigurationMetadata, getBeanClassLoader());
-		ConditionOutcome[] secondHalf = secondHalfResolver.resolveOutcomes();
-		ConditionOutcome[] firstHalf = firstHalfResolver.resolveOutcomes();
-		ConditionOutcome[] outcomes = new ConditionOutcome[autoConfigurationClasses.length];
+		@Nullable ConditionOutcome[] secondHalf = secondHalfResolver.resolveOutcomes();
+		@Nullable ConditionOutcome[] firstHalf = firstHalfResolver.resolveOutcomes();
+		@Nullable ConditionOutcome[] outcomes = new ConditionOutcome[autoConfigurationClasses.length];
 		System.arraycopy(firstHalf, 0, outcomes, 0, firstHalf.length);
 		System.arraycopy(secondHalf, 0, outcomes, split, secondHalf.length);
 		return outcomes;
 	}
 
-	private OutcomesResolver createOutcomesResolver(String[] autoConfigurationClasses, int start, int end,
+	private OutcomesResolver createOutcomesResolver(@Nullable String[] autoConfigurationClasses, int start, int end,
 			AutoConfigurationMetadata autoConfigurationMetadata) {
 		OutcomesResolver outcomesResolver = new StandardOutcomesResolver(autoConfigurationClasses, start, end,
 				autoConfigurationMetadata, getBeanClassLoader());
@@ -112,8 +114,9 @@ class OnClassCondition extends FilteringSpringBootCondition {
 		return ConditionOutcome.match(matchMessage);
 	}
 
-	private List<String> getCandidates(AnnotatedTypeMetadata metadata, Class<?> annotationType) {
-		MultiValueMap<String, Object> attributes = metadata.getAllAnnotationAttributes(annotationType.getName(), true);
+	private @Nullable List<String> getCandidates(AnnotatedTypeMetadata metadata, Class<?> annotationType) {
+		MultiValueMap<String, @Nullable Object> attributes = metadata
+			.getAllAnnotationAttributes(annotationType.getName(), true);
 		if (attributes == null) {
 			return null;
 		}
@@ -123,7 +126,7 @@ class OnClassCondition extends FilteringSpringBootCondition {
 		return candidates;
 	}
 
-	private void addAll(List<String> list, List<Object> itemsToAdd) {
+	private void addAll(List<String> list, @Nullable List<@Nullable Object> itemsToAdd) {
 		if (itemsToAdd != null) {
 			for (Object item : itemsToAdd) {
 				Collections.addAll(list, (String[]) item);
@@ -133,7 +136,7 @@ class OnClassCondition extends FilteringSpringBootCondition {
 
 	private interface OutcomesResolver {
 
-		ConditionOutcome[] resolveOutcomes();
+		@Nullable ConditionOutcome[] resolveOutcomes();
 
 	}
 
@@ -141,9 +144,9 @@ class OnClassCondition extends FilteringSpringBootCondition {
 
 		private final Thread thread;
 
-		private volatile ConditionOutcome[] outcomes;
+		private volatile @Nullable ConditionOutcome @Nullable [] outcomes;
 
-		private volatile Throwable failure;
+		private volatile @Nullable Throwable failure;
 
 		private ThreadedOutcomesResolver(OutcomesResolver outcomesResolver) {
 			this.thread = new Thread(() -> {
@@ -158,7 +161,7 @@ class OnClassCondition extends FilteringSpringBootCondition {
 		}
 
 		@Override
-		public ConditionOutcome[] resolveOutcomes() {
+		public @Nullable ConditionOutcome[] resolveOutcomes() {
 			try {
 				this.thread.join();
 			}
@@ -169,7 +172,7 @@ class OnClassCondition extends FilteringSpringBootCondition {
 			if (failure != null) {
 				ReflectionUtils.rethrowRuntimeException(failure);
 			}
-			ConditionOutcome[] outcomes = this.outcomes;
+			@Nullable ConditionOutcome[] outcomes = this.outcomes;
 			return (outcomes != null) ? outcomes : new ConditionOutcome[0];
 		}
 
@@ -177,7 +180,7 @@ class OnClassCondition extends FilteringSpringBootCondition {
 
 	private static final class StandardOutcomesResolver implements OutcomesResolver {
 
-		private final String[] autoConfigurationClasses;
+		private final @Nullable String[] autoConfigurationClasses;
 
 		private final int start;
 
@@ -187,7 +190,7 @@ class OnClassCondition extends FilteringSpringBootCondition {
 
 		private final ClassLoader beanClassLoader;
 
-		private StandardOutcomesResolver(String[] autoConfigurationClasses, int start, int end,
+		private StandardOutcomesResolver(@Nullable String[] autoConfigurationClasses, int start, int end,
 				AutoConfigurationMetadata autoConfigurationMetadata, ClassLoader beanClassLoader) {
 			this.autoConfigurationClasses = autoConfigurationClasses;
 			this.start = start;
@@ -197,13 +200,13 @@ class OnClassCondition extends FilteringSpringBootCondition {
 		}
 
 		@Override
-		public ConditionOutcome[] resolveOutcomes() {
+		public @Nullable ConditionOutcome[] resolveOutcomes() {
 			return getOutcomes(this.autoConfigurationClasses, this.start, this.end, this.autoConfigurationMetadata);
 		}
 
-		private ConditionOutcome[] getOutcomes(String[] autoConfigurationClasses, int start, int end,
-				AutoConfigurationMetadata autoConfigurationMetadata) {
-			ConditionOutcome[] outcomes = new ConditionOutcome[end - start];
+		private @Nullable ConditionOutcome[] getOutcomes(@Nullable String[] autoConfigurationClasses, int start,
+				int end, AutoConfigurationMetadata autoConfigurationMetadata) {
+			@Nullable ConditionOutcome[] outcomes = new ConditionOutcome[end - start];
 			for (int i = start; i < end; i++) {
 				String autoConfigurationClass = autoConfigurationClasses[i];
 				if (autoConfigurationClass != null) {
@@ -216,7 +219,7 @@ class OnClassCondition extends FilteringSpringBootCondition {
 			return outcomes;
 		}
 
-		private ConditionOutcome getOutcome(String candidates) {
+		private @Nullable ConditionOutcome getOutcome(String candidates) {
 			try {
 				if (!candidates.contains(",")) {
 					return getOutcome(candidates, this.beanClassLoader);
@@ -234,7 +237,7 @@ class OnClassCondition extends FilteringSpringBootCondition {
 			return null;
 		}
 
-		private ConditionOutcome getOutcome(String className, ClassLoader classLoader) {
+		private @Nullable ConditionOutcome getOutcome(String className, ClassLoader classLoader) {
 			if (ClassNameFilter.MISSING.matches(className, classLoader)) {
 				return ConditionOutcome.noMatch(ConditionMessage.forCondition(ConditionalOnClass.class)
 					.didNotFind("required class")

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/OnCloudPlatformCondition.java

@@ -18,11 +18,14 @@ package org.springframework.boot.autoconfigure.condition;
 
 import java.util.Map;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.cloud.CloudPlatform;
 import org.springframework.context.annotation.Condition;
 import org.springframework.context.annotation.ConditionContext;
 import org.springframework.core.env.Environment;
 import org.springframework.core.type.AnnotatedTypeMetadata;
+import org.springframework.util.Assert;
 
 /**
  * {@link Condition} that checks for a required {@link CloudPlatform}.
@@ -34,8 +37,11 @@ class OnCloudPlatformCondition extends SpringBootCondition {
 
 	@Override
 	public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
-		Map<String, Object> attributes = metadata.getAnnotationAttributes(ConditionalOnCloudPlatform.class.getName());
+		Map<String, @Nullable Object> attributes = metadata
+			.getAnnotationAttributes(ConditionalOnCloudPlatform.class.getName());
+		Assert.state(attributes != null, "'attributes' must not be null");
 		CloudPlatform cloudPlatform = (CloudPlatform) attributes.get("value");
+		Assert.state(cloudPlatform != null, "'cloudPlatform' must not be null");
 		return getMatchOutcome(context.getEnvironment(), cloudPlatform);
 	}
 

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/OnExpressionCondition.java

@@ -16,6 +16,10 @@
 
 package org.springframework.boot.autoconfigure.condition;
 
+import java.util.Map;
+
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.beans.factory.config.BeanExpressionContext;
 import org.springframework.beans.factory.config.BeanExpressionResolver;
 import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
@@ -24,6 +28,7 @@ import org.springframework.context.expression.StandardBeanExpressionResolver;
 import org.springframework.core.Ordered;
 import org.springframework.core.annotation.Order;
 import org.springframework.core.type.AnnotatedTypeMetadata;
+import org.springframework.util.Assert;
 
 /**
  * A Condition that evaluates a SpEL expression.
@@ -37,8 +42,11 @@ class OnExpressionCondition extends SpringBootCondition {
 
 	@Override
 	public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
-		String expression = (String) metadata.getAnnotationAttributes(ConditionalOnExpression.class.getName())
-			.get("value");
+		Map<String, @Nullable Object> attributes = metadata
+			.getAnnotationAttributes(ConditionalOnExpression.class.getName());
+		Assert.state(attributes != null, "'attributes' must not be null");
+		String expression = (String) attributes.get("value");
+		Assert.state(expression != null, "'expression' must not be null");
 		expression = wrapIfNecessary(expression);
 		ConditionMessage.Builder messageBuilder = ConditionMessage.forCondition(ConditionalOnExpression.class,
 				"(" + expression + ")");

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/OnJavaCondition.java

@@ -18,6 +18,8 @@ package org.springframework.boot.autoconfigure.condition;
 
 import java.util.Map;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.autoconfigure.condition.ConditionalOnJava.Range;
 import org.springframework.boot.system.JavaVersion;
 import org.springframework.context.annotation.Condition;
@@ -25,6 +27,7 @@ import org.springframework.context.annotation.ConditionContext;
 import org.springframework.core.Ordered;
 import org.springframework.core.annotation.Order;
 import org.springframework.core.type.AnnotatedTypeMetadata;
+import org.springframework.util.Assert;
 
 /**
  * {@link Condition} that checks for a required version of Java.
@@ -40,9 +43,12 @@ class OnJavaCondition extends SpringBootCondition {
 
 	@Override
 	public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
-		Map<String, Object> attributes = metadata.getAnnotationAttributes(ConditionalOnJava.class.getName());
+		Map<String, @Nullable Object> attributes = metadata.getAnnotationAttributes(ConditionalOnJava.class.getName());
+		Assert.state(attributes != null, "'attributes' must not be null");
 		Range range = (Range) attributes.get("range");
+		Assert.state(range != null, "'range' must not be null");
 		JavaVersion version = (JavaVersion) attributes.get("value");
+		Assert.state(version != null, "'version' must not be null");
 		return getMatchOutcome(range, JVM_VERSION, version);
 	}
 

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/OnJndiCondition.java

@@ -18,6 +18,8 @@ package org.springframework.boot.autoconfigure.condition;
 
 import javax.naming.NamingException;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.context.annotation.Condition;
 import org.springframework.context.annotation.ConditionContext;
 import org.springframework.core.Ordered;
@@ -26,6 +28,7 @@ import org.springframework.core.annotation.Order;
 import org.springframework.core.type.AnnotatedTypeMetadata;
 import org.springframework.jndi.JndiLocatorDelegate;
 import org.springframework.jndi.JndiLocatorSupport;
+import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
 /**
@@ -39,9 +42,10 @@ class OnJndiCondition extends SpringBootCondition {
 
 	@Override
 	public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
-		AnnotationAttributes annotationAttributes = AnnotationAttributes
+		AnnotationAttributes attributes = AnnotationAttributes
 			.fromMap(metadata.getAnnotationAttributes(ConditionalOnJndi.class.getName()));
-		String[] locations = annotationAttributes.getStringArray("value");
+		Assert.state(attributes != null, "'attributes' must not be null");
+		String[] locations = attributes.getStringArray("value");
 		try {
 			return getMatchOutcome(locations);
 		}
@@ -88,7 +92,7 @@ class OnJndiCondition extends SpringBootCondition {
 			this.locations = locations;
 		}
 
-		public String lookupFirstLocation() {
+		public @Nullable String lookupFirstLocation() {
 			for (String location : this.locations) {
 				try {
 					lookup(location);

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/OnPropertyCondition.java

@@ -22,6 +22,8 @@ import java.util.Arrays;
 import java.util.List;
 import java.util.stream.Stream;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.autoconfigure.condition.ConditionMessage.Style;
 import org.springframework.context.annotation.Condition;
 import org.springframework.context.annotation.ConditionContext;
@@ -129,10 +131,16 @@ class OnPropertyCondition extends SpringBootCondition {
 			this.annotationType = annotationType;
 			this.prefix = (!annotationAttributes.containsKey("prefix")) ? "" : getPrefix(annotationAttributes);
 			this.names = getNames(annotationAttributes);
-			this.havingValue = annotationAttributes.get("havingValue").toString();
+			this.havingValue = getHavingValue(annotationAttributes);
 			this.matchIfMissing = annotationAttributes.getBoolean("matchIfMissing");
 		}
 
+		private static String getHavingValue(AnnotationAttributes annotationAttributes) {
+			Object havingValue = annotationAttributes.get("havingValue");
+			Assert.state(havingValue != null, "'havingValue' must not be null");
+			return havingValue.toString();
+		}
+
 		private String getPrefix(AnnotationAttributes annotationAttributes) {
 			String prefix = annotationAttributes.getString("prefix").trim();
 			if (StringUtils.hasText(prefix) && !prefix.endsWith(".")) {
@@ -144,6 +152,8 @@ class OnPropertyCondition extends SpringBootCondition {
 		private String[] getNames(AnnotationAttributes annotationAttributes) {
 			String[] value = (String[]) annotationAttributes.get("value");
 			String[] name = (String[]) annotationAttributes.get("name");
+			Assert.state(value != null, "'value' must not be null");
+			Assert.state(name != null, "'name' must not be null");
 			Assert.state(value.length > 0 || name.length > 0,
 					() -> "The name or value attribute of @%s must be specified"
 						.formatted(ClassUtils.getShortName(this.annotationType)));
@@ -169,7 +179,7 @@ class OnPropertyCondition extends SpringBootCondition {
 			}
 		}
 
-		private boolean isMatch(String value, String requiredValue) {
+		private boolean isMatch(@Nullable String value, String requiredValue) {
 			if (StringUtils.hasLength(requiredValue)) {
 				return requiredValue.equalsIgnoreCase(value);
 			}

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/OnResourceCondition.java

@@ -19,6 +19,8 @@ package org.springframework.boot.autoconfigure.condition;
 import java.util.ArrayList;
 import java.util.List;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.autoconfigure.condition.ConditionMessage.Style;
 import org.springframework.context.annotation.Condition;
 import org.springframework.context.annotation.ConditionContext;
@@ -40,11 +42,14 @@ class OnResourceCondition extends SpringBootCondition {
 
 	@Override
 	public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
-		MultiValueMap<String, Object> attributes = metadata
+		MultiValueMap<String, @Nullable Object> attributes = metadata
 			.getAllAnnotationAttributes(ConditionalOnResource.class.getName(), true);
+		Assert.state(attributes != null, "'attributes' must not be null");
 		ResourceLoader loader = context.getResourceLoader();
 		List<String> locations = new ArrayList<>();
-		collectValues(locations, attributes.get("resources"));
+		List<@Nullable Object> resources = attributes.get("resources");
+		Assert.state(resources != null, "'resources' must not be null");
+		collectValues(locations, resources);
 		Assert.state(!locations.isEmpty(),
 				"@ConditionalOnResource annotations must specify at least one resource location");
 		List<String> missing = new ArrayList<>();
@@ -64,10 +69,13 @@ class OnResourceCondition extends SpringBootCondition {
 			.items(locations));
 	}
 
-	private void collectValues(List<String> names, List<Object> values) {
-		for (Object value : values) {
-			for (Object item : (Object[]) value) {
-				names.add((String) item);
+	private void collectValues(List<String> names, List<@Nullable Object> resources) {
+		for (Object resource : resources) {
+			Object[] items = (Object[]) resource;
+			if (items != null) {
+				for (Object item : items) {
+					names.add((String) item);
+				}
 			}
 		}
 	}

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/OnThreadingCondition.java

@@ -18,11 +18,14 @@ package org.springframework.boot.autoconfigure.condition;
 
 import java.util.Map;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.thread.Threading;
 import org.springframework.context.annotation.Condition;
 import org.springframework.context.annotation.ConditionContext;
 import org.springframework.core.env.Environment;
 import org.springframework.core.type.AnnotatedTypeMetadata;
+import org.springframework.util.Assert;
 
 /**
  * {@link Condition} that checks for a required {@link Threading}.
@@ -34,8 +37,11 @@ class OnThreadingCondition extends SpringBootCondition {
 
 	@Override
 	public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
-		Map<String, Object> attributes = metadata.getAnnotationAttributes(ConditionalOnThreading.class.getName());
+		Map<String, @Nullable Object> attributes = metadata
+			.getAnnotationAttributes(ConditionalOnThreading.class.getName());
+		Assert.state(attributes != null, "'attributes' must not be null");
 		Threading threading = (Threading) attributes.get("value");
+		Assert.state(threading != null, "'threading' must not be null");
 		return getMatchOutcome(context.getEnvironment(), threading);
 	}
 

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/OnWebApplicationCondition.java

@@ -18,6 +18,8 @@ package org.springframework.boot.autoconfigure.condition;
 
 import java.util.Map;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.autoconfigure.AutoConfigurationMetadata;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication.Type;
 import org.springframework.boot.web.context.reactive.ConfigurableReactiveWebEnvironment;
@@ -27,6 +29,7 @@ import org.springframework.context.annotation.ConditionContext;
 import org.springframework.core.Ordered;
 import org.springframework.core.annotation.Order;
 import org.springframework.core.type.AnnotatedTypeMetadata;
+import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.ObjectUtils;
 import org.springframework.web.context.ConfigurableWebEnvironment;
@@ -49,9 +52,9 @@ class OnWebApplicationCondition extends FilteringSpringBootCondition {
 	private static final String REACTIVE_WEB_APPLICATION_CLASS = "org.springframework.web.reactive.HandlerResult";
 
 	@Override
-	protected ConditionOutcome[] getOutcomes(String[] autoConfigurationClasses,
+	protected @Nullable ConditionOutcome[] getOutcomes(@Nullable String[] autoConfigurationClasses,
 			AutoConfigurationMetadata autoConfigurationMetadata) {
-		ConditionOutcome[] outcomes = new ConditionOutcome[autoConfigurationClasses.length];
+		@Nullable ConditionOutcome[] outcomes = new ConditionOutcome[autoConfigurationClasses.length];
 		for (int i = 0; i < outcomes.length; i++) {
 			String autoConfigurationClass = autoConfigurationClasses[i];
 			if (autoConfigurationClass != null) {
@@ -62,7 +65,7 @@ class OnWebApplicationCondition extends FilteringSpringBootCondition {
 		return outcomes;
 	}
 
-	private ConditionOutcome getOutcome(String type) {
+	private @Nullable ConditionOutcome getOutcome(@Nullable String type) {
 		if (type == null) {
 			return null;
 		}
@@ -157,9 +160,12 @@ class OnWebApplicationCondition extends FilteringSpringBootCondition {
 	}
 
 	private Type deduceType(AnnotatedTypeMetadata metadata) {
-		Map<String, Object> attributes = metadata.getAnnotationAttributes(ConditionalOnWebApplication.class.getName());
+		Map<String, @Nullable Object> attributes = metadata
+			.getAnnotationAttributes(ConditionalOnWebApplication.class.getName());
 		if (attributes != null) {
-			return (Type) attributes.get("type");
+			Object type = attributes.get("type");
+			Assert.state(type != null, "'type' must not be null");
+			return (Type) type;
 		}
 		return Type.ANY;
 	}

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/package-info.java

@@ -17,4 +17,7 @@
 /**
  * {@code @Condition} annotations and supporting classes.
  */
+@NullMarked
 package org.springframework.boot.autoconfigure.condition;
+
+import org.jspecify.annotations.NullMarked;

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/container/ContainerImageMetadata.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.autoconfigure.container;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.core.AttributeAccessor;
 
@@ -29,7 +31,7 @@ import org.springframework.core.AttributeAccessor;
  * @author Phillip Webb
  * @since 3.4.0
  */
-public record ContainerImageMetadata(String imageName) {
+public record ContainerImageMetadata(@Nullable String imageName) {
 
 	static final String NAME = ContainerImageMetadata.class.getName();
 
@@ -37,7 +39,7 @@ public record ContainerImageMetadata(String imageName) {
 	 * Add this container image metadata to the given attributes.
 	 * @param attributes the attributes to add the metadata to
 	 */
-	public void addTo(AttributeAccessor attributes) {
+	public void addTo(@Nullable AttributeAccessor attributes) {
 		if (attributes != null) {
 			attributes.setAttribute(NAME, this);
 		}
@@ -49,7 +51,7 @@ public record ContainerImageMetadata(String imageName) {
 	 * @param attributes the attributes to check
 	 * @return if metadata is present
 	 */
-	public static boolean isPresent(AttributeAccessor attributes) {
+	public static boolean isPresent(@Nullable AttributeAccessor attributes) {
 		return getFrom(attributes) != null;
 	}
 
@@ -59,7 +61,7 @@ public record ContainerImageMetadata(String imageName) {
 	 * @param attributes the attributes
 	 * @return the metadata or {@code null}
 	 */
-	public static ContainerImageMetadata getFrom(AttributeAccessor attributes) {
+	public static @Nullable ContainerImageMetadata getFrom(@Nullable AttributeAccessor attributes) {
 		return (attributes != null) ? (ContainerImageMetadata) attributes.getAttribute(NAME) : null;
 	}
 

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/container/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Support classes related to auto-configuration involving containers.
  */
+@NullMarked
 package org.springframework.boot.autoconfigure.container;
+
+import org.jspecify.annotations.NullMarked;

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/context/MessageSourceAutoConfiguration.java

@@ -22,6 +22,8 @@ import java.time.Duration;
 import java.util.List;
 import java.util.Properties;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.aot.hint.RuntimeHints;
 import org.springframework.aot.hint.RuntimeHintsRegistrar;
 import org.springframework.boot.autoconfigure.AutoConfiguration;
@@ -92,7 +94,7 @@ public final class MessageSourceAutoConfiguration {
 		return messageSource;
 	}
 
-	private Properties loadCommonMessages(List<Resource> resources) {
+	private @Nullable Properties loadCommonMessages(@Nullable List<Resource> resources) {
 		if (CollectionUtils.isEmpty(resources)) {
 			return null;
 		}
@@ -135,7 +137,7 @@ public final class MessageSourceAutoConfiguration {
 			return ConditionOutcome.noMatch(message.didNotFind("bundle with basename " + basename).atAll());
 		}
 
-		private Resource[] getResources(ClassLoader classLoader, String name) {
+		private Resource[] getResources(@Nullable ClassLoader classLoader, String name) {
 			String target = name.replace('.', '/');
 			try {
 				return new PathMatchingResourcePatternResolver(classLoader)
@@ -151,7 +153,7 @@ public final class MessageSourceAutoConfiguration {
 	static class MessageSourceRuntimeHints implements RuntimeHintsRegistrar {
 
 		@Override
-		public void registerHints(RuntimeHints hints, ClassLoader classLoader) {
+		public void registerHints(RuntimeHints hints, @Nullable ClassLoader classLoader) {
 			hints.resources().registerPattern("messages.properties").registerPattern("messages_*.properties");
 		}
 

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/context/MessageSourceProperties.java

@@ -23,6 +23,8 @@ import java.time.temporal.ChronoUnit;
 import java.util.ArrayList;
 import java.util.List;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.context.properties.ConfigurationProperties;
 import org.springframework.boot.convert.DurationUnit;
 import org.springframework.core.io.Resource;
@@ -49,7 +51,7 @@ public class MessageSourceProperties {
 	/**
 	 * List of locale-independent property file resources containing common messages.
 	 */
-	private List<Resource> commonMessages;
+	private @Nullable List<Resource> commonMessages;
 
 	/**
 	 * Message bundles encoding.
@@ -61,7 +63,7 @@ public class MessageSourceProperties {
 	 * forever. If a duration suffix is not specified, seconds will be used.
 	 */
 	@DurationUnit(ChronoUnit.SECONDS)
-	private Duration cacheDuration;
+	private @Nullable Duration cacheDuration;
 
 	/**
 	 * Whether to fall back to the system Locale if no files for a specific Locale have
@@ -98,11 +100,11 @@ public class MessageSourceProperties {
 		this.encoding = encoding;
 	}
 
-	public Duration getCacheDuration() {
+	public @Nullable Duration getCacheDuration() {
 		return this.cacheDuration;
 	}
 
-	public void setCacheDuration(Duration cacheDuration) {
+	public void setCacheDuration(@Nullable Duration cacheDuration) {
 		this.cacheDuration = cacheDuration;
 	}
 
@@ -130,11 +132,11 @@ public class MessageSourceProperties {
 		this.useCodeAsDefaultMessage = useCodeAsDefaultMessage;
 	}
 
-	public List<Resource> getCommonMessages() {
+	public @Nullable List<Resource> getCommonMessages() {
 		return this.commonMessages;
 	}
 
-	public void setCommonMessages(List<Resource> commonMessages) {
+	public void setCommonMessages(@Nullable List<Resource> commonMessages) {
 		this.commonMessages = commonMessages;
 	}
 

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/context/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Auto-configuration for the Spring context.
  */
+@NullMarked
 package org.springframework.boot.autoconfigure.context;
+
+import org.jspecify.annotations.NullMarked;

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/data/AbstractRepositoryConfigurationSourceSupport.java

@@ -18,6 +18,8 @@ package org.springframework.boot.autoconfigure.data;
 
 import java.lang.annotation.Annotation;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.BeanFactoryAware;
@@ -48,15 +50,18 @@ import org.springframework.data.util.Streamable;
 public abstract class AbstractRepositoryConfigurationSourceSupport
 		implements ImportBeanDefinitionRegistrar, BeanFactoryAware, ResourceLoaderAware, EnvironmentAware {
 
+	@SuppressWarnings("NullAway.Init")
 	private ResourceLoader resourceLoader;
 
+	@SuppressWarnings("NullAway.Init")
 	private BeanFactory beanFactory;
 
+	@SuppressWarnings("NullAway.Init")
 	private Environment environment;
 
 	@Override
 	public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry,
-			BeanNameGenerator importBeanNameGenerator) {
+			@Nullable BeanNameGenerator importBeanNameGenerator) {
 		RepositoryConfigurationDelegate delegate = new RepositoryConfigurationDelegate(
 				getConfigurationSource(registry, importBeanNameGenerator), this.resourceLoader, this.environment);
 		delegate.registerRepositoriesIn(registry, getRepositoryConfigurationExtension());
@@ -68,7 +73,7 @@ public abstract class AbstractRepositoryConfigurationSourceSupport
 	}
 
 	private AnnotationRepositoryConfigurationSource getConfigurationSource(BeanDefinitionRegistry registry,
-			BeanNameGenerator importBeanNameGenerator) {
+			@Nullable BeanNameGenerator importBeanNameGenerator) {
 		AnnotationMetadata metadata = AnnotationMetadata.introspect(getConfiguration());
 		return new AutoConfiguredAnnotationRepositoryConfigurationSource(metadata, getAnnotation(), this.resourceLoader,
 				this.environment, registry, importBeanNameGenerator) {
@@ -129,7 +134,7 @@ public abstract class AbstractRepositoryConfigurationSourceSupport
 
 		AutoConfiguredAnnotationRepositoryConfigurationSource(AnnotationMetadata metadata,
 				Class<? extends Annotation> annotation, ResourceLoader resourceLoader, Environment environment,
-				BeanDefinitionRegistry registry, BeanNameGenerator generator) {
+				BeanDefinitionRegistry registry, @Nullable BeanNameGenerator generator) {
 			super(metadata, annotation, resourceLoader, environment, registry, generator);
 		}
 

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/data/OnRepositoryTypeCondition.java

@@ -19,12 +19,15 @@ package org.springframework.boot.autoconfigure.data;
 import java.util.Locale;
 import java.util.Map;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.autoconfigure.condition.ConditionMessage;
 import org.springframework.boot.autoconfigure.condition.ConditionOutcome;
 import org.springframework.boot.autoconfigure.condition.SpringBootCondition;
 import org.springframework.context.annotation.ConditionContext;
 import org.springframework.core.env.Environment;
 import org.springframework.core.type.AnnotatedTypeMetadata;
+import org.springframework.util.Assert;
 
 /**
  * {@link SpringBootCondition} for controlling what type of Spring Data repositories are
@@ -36,10 +39,14 @@ class OnRepositoryTypeCondition extends SpringBootCondition {
 
 	@Override
 	public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
-		Map<String, Object> attributes = metadata.getAnnotationAttributes(ConditionalOnRepositoryType.class.getName(),
-				true);
-		RepositoryType configuredType = getTypeProperty(context.getEnvironment(), (String) attributes.get("store"));
+		Map<String, @Nullable Object> attributes = metadata
+			.getAnnotationAttributes(ConditionalOnRepositoryType.class.getName(), true);
+		Assert.state(attributes != null, "'attributes' must not be null");
+		String store = (String) attributes.get("store");
+		Assert.state(store != null, "'store' must not be null");
+		RepositoryType configuredType = getTypeProperty(context.getEnvironment(), store);
 		RepositoryType requiredType = (RepositoryType) attributes.get("type");
+		Assert.state(requiredType != null, "'requiredType' must not be null");
 		ConditionMessage.Builder message = ConditionMessage.forCondition(ConditionalOnRepositoryType.class);
 		if (configuredType == requiredType || configuredType == RepositoryType.AUTO) {
 			return ConditionOutcome

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/data/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Auto-configuration base classes for Spring Data.
  */
+@NullMarked
 package org.springframework.boot.autoconfigure.data;
+
+import org.jspecify.annotations.NullMarked;

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/diagnostics/analyzer/NoSuchBeanDefinitionFailureAnalyzer.java

@@ -25,6 +25,8 @@ import java.util.List;
 import java.util.Map;
 import java.util.Set;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.BeanFactoryUtils;
 import org.springframework.beans.factory.InjectionPoint;
@@ -74,7 +76,8 @@ class NoSuchBeanDefinitionFailureAnalyzer extends AbstractInjectionFailureAnalyz
 	}
 
 	@Override
-	protected FailureAnalysis analyze(Throwable rootFailure, NoSuchBeanDefinitionException cause, String description) {
+	protected @Nullable FailureAnalysis analyze(Throwable rootFailure, NoSuchBeanDefinitionException cause,
+			@Nullable String description) {
 		if (cause.getNumberOfBeansFound() != 0) {
 			return null;
 		}
@@ -118,7 +121,9 @@ class NoSuchBeanDefinitionFailureAnalyzer extends AbstractInjectionFailureAnalyz
 	}
 
 	private Class<?> extractBeanType(ResolvableType resolvableType) {
-		return resolvableType.getRawClass();
+		Class<?> rawClass = resolvableType.getRawClass();
+		Assert.state(rawClass != null, "'rawClass' must not be null");
+		return rawClass;
 	}
 
 	private List<AutoConfigurationResult> getAutoConfigurationResults(NoSuchBeanDefinitionException cause) {
@@ -140,7 +145,7 @@ class NoSuchBeanDefinitionFailureAnalyzer extends AbstractInjectionFailureAnalyz
 			.toList();
 	}
 
-	private MethodMetadata getFactoryMethodMetadata(String beanName) {
+	private @Nullable MethodMetadata getFactoryMethodMetadata(String beanName) {
 		BeanDefinition beanDefinition = this.beanFactory.getBeanDefinition(beanName);
 		if (beanDefinition instanceof AnnotatedBeanDefinition annotatedBeanDefinition) {
 			return annotatedBeanDefinition.getFactoryMethodMetadata();
@@ -183,7 +188,7 @@ class NoSuchBeanDefinitionFailureAnalyzer extends AbstractInjectionFailureAnalyz
 		}
 	}
 
-	private InjectionPoint findInjectionPoint(Throwable failure) {
+	private @Nullable InjectionPoint findInjectionPoint(Throwable failure) {
 		UnsatisfiedDependencyException unsatisfiedDependencyException = findCause(failure,
 				UnsatisfiedDependencyException.class);
 		if (unsatisfiedDependencyException == null) {
@@ -196,7 +201,7 @@ class NoSuchBeanDefinitionFailureAnalyzer extends AbstractInjectionFailureAnalyz
 
 		private final String className;
 
-		private final String methodName;
+		private final @Nullable String methodName;
 
 		Source(String source) {
 			String[] tokens = source.split("#");
@@ -208,7 +213,7 @@ class NoSuchBeanDefinitionFailureAnalyzer extends AbstractInjectionFailureAnalyz
 			return this.className;
 		}
 
-		String getMethodName() {
+		@Nullable String getMethodName() {
 			return this.methodName;
 		}
 
@@ -252,7 +257,7 @@ class NoSuchBeanDefinitionFailureAnalyzer extends AbstractInjectionFailureAnalyz
 		}
 
 		private boolean hasName(MethodMetadata methodMetadata, String name) {
-			Map<String, Object> attributes = methodMetadata.getAnnotationAttributes(Bean.class.getName());
+			Map<String, @Nullable Object> attributes = methodMetadata.getAnnotationAttributes(Bean.class.getName());
 			String[] candidates = (attributes != null) ? (String[]) attributes.get("name") : null;
 			if (candidates != null) {
 				for (String candidate : candidates) {
@@ -309,11 +314,11 @@ class NoSuchBeanDefinitionFailureAnalyzer extends AbstractInjectionFailureAnalyz
 
 	private static class UserConfigurationResult {
 
-		private final MethodMetadata methodMetadata;
+		private final @Nullable MethodMetadata methodMetadata;
 
 		private final boolean nullBean;
 
-		UserConfigurationResult(MethodMetadata methodMetadata, boolean nullBean) {
+		UserConfigurationResult(@Nullable MethodMetadata methodMetadata, boolean nullBean) {
 			this.methodMetadata = methodMetadata;
 			this.nullBean = nullBean;
 		}

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/diagnostics/analyzer/package-info.java

@@ -18,4 +18,7 @@
  * Internal {@link org.springframework.boot.diagnostics.FailureAnalyzer} implementations
  * related to auto-configuration.
  */
+@NullMarked
 package org.springframework.boot.autoconfigure.diagnostics.analyzer;
+
+import org.jspecify.annotations.NullMarked;

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/domain/EntityScanPackages.java

@@ -139,6 +139,7 @@ public class EntityScanPackages {
 		private Set<String> getPackagesToScan(AnnotationMetadata metadata) {
 			AnnotationAttributes attributes = AnnotationAttributes
 				.fromMap(metadata.getAnnotationAttributes(EntityScan.class.getName()));
+			Assert.state(attributes != null, "'attributes' must not be null");
 			Set<String> packagesToScan = new LinkedHashSet<>();
 			for (String basePackage : attributes.getStringArray("basePackages")) {
 				String[] tokenized = StringUtils.tokenizeToStringArray(

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/domain/EntityScanner.java

@@ -72,7 +72,9 @@ public class EntityScanner {
 		for (String basePackage : packages) {
 			if (StringUtils.hasText(basePackage)) {
 				for (BeanDefinition candidate : scanner.findCandidateComponents(basePackage)) {
-					entitySet.add(ClassUtils.forName(candidate.getBeanClassName(), this.context.getClassLoader()));
+					String beanClassName = candidate.getBeanClassName();
+					Assert.state(beanClassName != null, "'beanClassName' must not be null");
+					entitySet.add(ClassUtils.forName(beanClassName, this.context.getClassLoader()));
 				}
 			}
 		}

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/domain/package-info.java

@@ -17,4 +17,7 @@
 /**
  * General purpose domain annotations and classes.
  */
+@NullMarked
 package org.springframework.boot.autoconfigure.domain;
+
+import org.jspecify.annotations.NullMarked;

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/info/ProjectInfoAutoConfiguration.java

@@ -20,6 +20,8 @@ import java.io.IOException;
 import java.nio.charset.Charset;
 import java.util.Properties;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.autoconfigure.AutoConfiguration;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.autoconfigure.condition.ConditionMessage;
@@ -85,7 +87,7 @@ public final class ProjectInfoAutoConfiguration {
 		return target;
 	}
 
-	private Properties loadSource(Resource location, Charset encoding) throws IOException {
+	private Properties loadSource(Resource location, @Nullable Charset encoding) throws IOException {
 		if (encoding != null) {
 			return PropertiesLoaderUtils.loadProperties(new EncodedResource(location, encoding));
 		}

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/info/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Auto-configuration for project information.
  */
+@NullMarked
 package org.springframework.boot.autoconfigure.info;
+
+import org.jspecify.annotations.NullMarked;

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jmx/JmxAutoConfiguration.java

@@ -34,6 +34,7 @@ import org.springframework.jmx.export.annotation.AnnotationJmxAttributeSource;
 import org.springframework.jmx.export.annotation.AnnotationMBeanExporter;
 import org.springframework.jmx.export.naming.ObjectNamingStrategy;
 import org.springframework.jmx.support.MBeanServerFactoryBean;
+import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
 /**
@@ -94,7 +95,9 @@ public final class JmxAutoConfiguration {
 		MBeanServerFactoryBean factory = new MBeanServerFactoryBean();
 		factory.setLocateExistingServerIfPossible(true);
 		factory.afterPropertiesSet();
-		return factory.getObject();
+		MBeanServer mBeanServer = factory.getObject();
+		Assert.state(mBeanServer != null, "'mBeanServer' must not be null");
+		return mBeanServer;
 	}
 
 }

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jmx/JmxProperties.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.autoconfigure.jmx;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.context.properties.ConfigurationProperties;
 import org.springframework.jmx.support.RegistrationPolicy;
 
@@ -46,7 +48,7 @@ public class JmxProperties {
 	/**
 	 * JMX domain name.
 	 */
-	private String defaultDomain;
+	private @Nullable String defaultDomain;
 
 	/**
 	 * JMX Registration policy.
@@ -77,11 +79,11 @@ public class JmxProperties {
 		this.server = server;
 	}
 
-	public String getDefaultDomain() {
+	public @Nullable String getDefaultDomain() {
 		return this.defaultDomain;
 	}
 
-	public void setDefaultDomain(String defaultDomain) {
+	public void setDefaultDomain(@Nullable String defaultDomain) {
 		this.defaultDomain = defaultDomain;
 	}
 

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jmx/ParentAwareNamingStrategy.java

@@ -21,6 +21,8 @@ import java.util.Hashtable;
 import javax.management.MalformedObjectNameException;
 import javax.management.ObjectName;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.beans.BeansException;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextAware;
@@ -28,6 +30,7 @@ import org.springframework.jmx.export.metadata.JmxAttributeSource;
 import org.springframework.jmx.export.naming.MetadataNamingStrategy;
 import org.springframework.jmx.support.JmxUtils;
 import org.springframework.jmx.support.ObjectNameManager;
+import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 
 /**
@@ -39,6 +42,7 @@ import org.springframework.util.ObjectUtils;
  */
 public class ParentAwareNamingStrategy extends MetadataNamingStrategy implements ApplicationContextAware {
 
+	@SuppressWarnings("NullAway.Init")
 	private ApplicationContext applicationContext;
 
 	private boolean ensureUniqueRuntimeObjectNames;
@@ -62,7 +66,7 @@ public class ParentAwareNamingStrategy extends MetadataNamingStrategy implements
 	}
 
 	@Override
-	public ObjectName getObjectName(Object managedBean, String beanKey) throws MalformedObjectNameException {
+	public ObjectName getObjectName(Object managedBean, @Nullable String beanKey) throws MalformedObjectNameException {
 		ObjectName name = super.getObjectName(managedBean, beanKey);
 		if (this.ensureUniqueRuntimeObjectNames) {
 			return JmxUtils.appendIdentityToObjectName(name, managedBean);
@@ -73,12 +77,15 @@ public class ParentAwareNamingStrategy extends MetadataNamingStrategy implements
 		return name;
 	}
 
-	private boolean parentContextContainsSameBean(ApplicationContext context, String beanKey) {
+	private boolean parentContextContainsSameBean(ApplicationContext context, @Nullable String beanKey) {
 		if (context.getParent() == null) {
 			return false;
 		}
 		try {
-			this.applicationContext.getParent().getBean(beanKey);
+			ApplicationContext parent = this.applicationContext.getParent();
+			Assert.state(parent != null, "'parent' must not be null");
+			Assert.state(beanKey != null, "'beanKey' must not be null");
+			parent.getBean(beanKey);
 			return true;
 		}
 		catch (BeansException ex) {

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jmx/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Auto-configuration for JMX.
  */
+@NullMarked
 package org.springframework.boot.autoconfigure.jmx;
+
+import org.jspecify.annotations.NullMarked;

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/logging/ConditionEvaluationReportLoggingListener.java

@@ -18,6 +18,8 @@ package org.springframework.boot.autoconfigure.logging;
 
 import java.util.function.Supplier;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.autoconfigure.condition.ConditionEvaluationReport;
 import org.springframework.boot.context.event.ApplicationFailedEvent;
 import org.springframework.boot.logging.LogLevel;
@@ -124,7 +126,7 @@ public class ConditionEvaluationReportLoggingListener
 		}
 
 		@Override
-		public boolean supportsSourceType(Class<?> sourceType) {
+		public boolean supportsSourceType(@Nullable Class<?> sourceType) {
 			return true;
 		}
 

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/logging/ConditionEvaluationReportLoggingProcessor.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.autoconfigure.logging;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.beans.factory.aot.BeanFactoryInitializationAotContribution;
 import org.springframework.beans.factory.aot.BeanFactoryInitializationAotProcessor;
 import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
@@ -31,7 +33,8 @@ import org.springframework.boot.logging.LogLevel;
 class ConditionEvaluationReportLoggingProcessor implements BeanFactoryInitializationAotProcessor {
 
 	@Override
-	public BeanFactoryInitializationAotContribution processAheadOfTime(ConfigurableListableBeanFactory beanFactory) {
+	public @Nullable BeanFactoryInitializationAotContribution processAheadOfTime(
+			ConfigurableListableBeanFactory beanFactory) {
 		logConditionEvaluationReport(beanFactory);
 		return null;
 	}

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/logging/ConditionEvaluationReportMessage.java

@@ -27,6 +27,7 @@ import java.util.Set;
 import org.springframework.boot.autoconfigure.condition.ConditionEvaluationReport;
 import org.springframework.boot.autoconfigure.condition.ConditionEvaluationReport.ConditionAndOutcome;
 import org.springframework.boot.autoconfigure.condition.ConditionEvaluationReport.ConditionAndOutcomes;
+import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
@@ -133,6 +134,7 @@ public class ConditionEvaluationReportMessage {
 		Map<String, ConditionAndOutcomes> result = new LinkedHashMap<>();
 		for (String shortName : shortNames) {
 			List<String> fullyQualifiedNames = map.get(shortName);
+			Assert.state(fullyQualifiedNames != null, "'fullyQualifiedNames' must not be null");
 			if (fullyQualifiedNames.size() > 1) {
 				fullyQualifiedNames
 					.forEach((fullyQualifiedName) -> result.put(fullyQualifiedName, outcomes.get(fullyQualifiedName)));

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/logging/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Auto-configuration for logging.
  */
+@NullMarked
 package org.springframework.boot.autoconfigure.logging;
+
+import org.jspecify.annotations.NullMarked;

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/package-info.java

@@ -19,4 +19,7 @@
  *
  * @see org.springframework.boot.autoconfigure.EnableAutoConfiguration
  */
+@NullMarked
 package org.springframework.boot.autoconfigure;
+
+import org.jspecify.annotations.NullMarked;

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/preinitialize/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Capabilities to preinitialize code in the background to improve startup performance.
  */
+@NullMarked
 package org.springframework.boot.autoconfigure.preinitialize;
+
+import org.jspecify.annotations.NullMarked;

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/service/connection/ConnectionDetailsFactories.java

@@ -26,6 +26,7 @@ import java.util.stream.Stream;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.core.ResolvableType;
 import org.springframework.core.annotation.AnnotationAwareOrderComparator;
@@ -53,7 +54,7 @@ public class ConnectionDetailsFactories {
 	 * @param classLoader the class loader used to load factories
 	 * @since 3.5.0
 	 */
-	public ConnectionDetailsFactories(ClassLoader classLoader) {
+	public ConnectionDetailsFactories(@Nullable ClassLoader classLoader) {
 		this(SpringFactoriesLoader.forDefaultResourceLocation(classLoader));
 	}
 
@@ -126,9 +127,10 @@ public class ConnectionDetailsFactories {
 			ConnectionDetailsFactory<S, D> factory) {
 
 		@SuppressWarnings("unchecked")
-		private static <S, D extends ConnectionDetails> Registration<S, D> get(ConnectionDetailsFactory<S, D> factory) {
+		private static <S, D extends ConnectionDetails> @Nullable Registration<S, D> get(
+				ConnectionDetailsFactory<S, D> factory) {
 			ResolvableType type = ResolvableType.forClass(ConnectionDetailsFactory.class, factory.getClass());
-			Class<?>[] generics = type.resolveGenerics();
+			@Nullable Class<?>[] generics = type.resolveGenerics();
 			Class<S> sourceType = (Class<S>) generics[0];
 			Class<D> connectionDetailsType = (Class<D>) generics[1];
 			return (sourceType != null && connectionDetailsType != null)

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/service/connection/ConnectionDetailsFactory.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.autoconfigure.service.connection;
 
+import org.jspecify.annotations.Nullable;
+
 /**
  * A factory to create {@link ConnectionDetails} from a given {@code source}.
  * Implementations should be registered in {@code META-INF/spring.factories}.
@@ -36,6 +38,6 @@ public interface ConnectionDetailsFactory<S, D extends ConnectionDetails> {
 	 * @param source the source
 	 * @return the connection details or {@code null}
 	 */
-	D getConnectionDetails(S source);
+	@Nullable D getConnectionDetails(S source);
 
 }

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/service/connection/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Support for service connections that affect auto-configuration.
  */
+@NullMarked
 package org.springframework.boot.autoconfigure.service.connection;
+
+import org.jspecify.annotations.NullMarked;

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/ssl/BundleContentProperty.java

@@ -18,6 +18,8 @@ package org.springframework.boot.autoconfigure.ssl;
 
 import java.nio.file.Path;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.ssl.pem.PemContent;
 import org.springframework.core.io.Resource;
 import org.springframework.core.io.ResourceLoader;
@@ -33,7 +35,7 @@ import org.springframework.util.StringUtils;
  * @author Phillip Webb
  * @author Moritz Halbritter
  */
-record BundleContentProperty(String name, String value) {
+record BundleContentProperty(String name, @Nullable String value) {
 
 	/**
 	 * Return if the property value is PEM content.
@@ -54,6 +56,7 @@ record BundleContentProperty(String name, String value) {
 	Path toWatchPath(ResourceLoader resourceLoader) {
 		try {
 			Assert.state(!isPemContent(), "Value contains PEM content");
+			Assert.state(this.value != null, "Value must not be null");
 			Resource resource = resourceLoader.getResource(this.value);
 			if (!resource.isFile()) {
 				throw new BundleContentNotWatchableException(this);

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/ssl/CertificateMatcher.java

@@ -26,6 +26,8 @@ import java.security.cert.Certificate;
 import java.util.List;
 import java.util.Objects;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.util.Assert;
 
 /**
@@ -47,17 +49,18 @@ class CertificateMatcher {
 
 	private final Signature signature;
 
-	private final byte[] generatedSignature;
+	private final byte @Nullable [] generatedSignature;
 
 	CertificateMatcher(PrivateKey privateKey) {
 		Assert.notNull(privateKey, "'privateKey' must not be null");
 		this.privateKey = privateKey;
-		this.signature = createSignature(privateKey);
-		Assert.state(this.signature != null, "Failed to create signature");
-		this.generatedSignature = sign(this.signature, privateKey);
+		Signature signature = createSignature(privateKey);
+		Assert.state(signature != null, "Failed to create signature");
+		this.signature = signature;
+		this.generatedSignature = sign(signature, privateKey);
 	}
 
-	private Signature createSignature(PrivateKey privateKey) {
+	private @Nullable Signature createSignature(PrivateKey privateKey) {
 		try {
 			String algorithm = getSignatureAlgorithm(privateKey);
 			return (algorithm != null) ? Signature.getInstance(algorithm) : null;
@@ -67,7 +70,7 @@ class CertificateMatcher {
 		}
 	}
 
-	private static String getSignatureAlgorithm(PrivateKey privateKey) {
+	private static @Nullable String getSignatureAlgorithm(PrivateKey privateKey) {
 		// https://docs.oracle.com/en/java/javase/17/docs/specs/security/standard-names.html#signature-algorithms
 		// https://docs.oracle.com/en/java/javase/17/docs/specs/security/standard-names.html#keypairgenerator-algorithms
 		return switch (privateKey.getAlgorithm()) {
@@ -103,7 +106,7 @@ class CertificateMatcher {
 		}
 	}
 
-	private static byte[] sign(Signature signature, PrivateKey privateKey) {
+	private static byte @Nullable [] sign(Signature signature, PrivateKey privateKey) {
 		try {
 			signature.initSign(privateKey);
 			signature.update(DATA);

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/ssl/FileWatcher.java

@@ -39,6 +39,7 @@ import java.util.concurrent.TimeUnit;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.core.log.LogMessage;
 import org.springframework.util.Assert;
@@ -57,7 +58,7 @@ class FileWatcher implements Closeable {
 
 	private final Object lock = new Object();
 
-	private WatcherThread thread;
+	private @Nullable WatcherThread thread;
 
 	/**
 	 * Create a new {@link FileWatcher} instance.
@@ -241,6 +242,7 @@ class FileWatcher implements Closeable {
 			Path directory = (Path) key.watchable();
 			for (WatchEvent<?> event : key.pollEvents()) {
 				Path file = directory.resolve((Path) event.context());
+				Assert.state(registrations != null, "'registrations' must not be null");
 				for (Registration registration : registrations) {
 					if (registration.manages(file)) {
 						actions.add(registration.action());

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/ssl/JksSslBundleProperties.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.autoconfigure.ssl;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.ssl.jks.JksSslStoreBundle;
 
 /**
@@ -54,52 +56,52 @@ public class JksSslBundleProperties extends SslBundleProperties {
 		/**
 		 * Type of the store to create, e.g. JKS.
 		 */
-		private String type;
+		private @Nullable String type;
 
 		/**
 		 * Provider for the store.
 		 */
-		private String provider;
+		private @Nullable String provider;
 
 		/**
 		 * Location of the resource containing the store content.
 		 */
-		private String location;
+		private @Nullable String location;
 
 		/**
 		 * Password used to access the store.
 		 */
-		private String password;
+		private @Nullable String password;
 
-		public String getType() {
+		public @Nullable String getType() {
 			return this.type;
 		}
 
-		public void setType(String type) {
+		public void setType(@Nullable String type) {
 			this.type = type;
 		}
 
-		public String getProvider() {
+		public @Nullable String getProvider() {
 			return this.provider;
 		}
 
-		public void setProvider(String provider) {
+		public void setProvider(@Nullable String provider) {
 			this.provider = provider;
 		}
 
-		public String getLocation() {
+		public @Nullable String getLocation() {
 			return this.location;
 		}
 
-		public void setLocation(String location) {
+		public void setLocation(@Nullable String location) {
 			this.location = location;
 		}
 
-		public String getPassword() {
+		public @Nullable String getPassword() {
 			return this.password;
 		}
 
-		public void setPassword(String password) {
+		public void setPassword(@Nullable String password) {
 			this.password = password;
 		}
 

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/ssl/PemSslBundleProperties.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.autoconfigure.ssl;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.ssl.pem.PemSslStoreBundle;
 
 /**
@@ -55,57 +57,57 @@ public class PemSslBundleProperties extends SslBundleProperties {
 		/**
 		 * Type of the store to create, e.g. JKS.
 		 */
-		private String type;
+		private @Nullable String type;
 
 		/**
 		 * Location or content of the certificate or certificate chain in PEM format.
 		 */
-		private String certificate;
+		private @Nullable String certificate;
 
 		/**
 		 * Location or content of the private key in PEM format.
 		 */
-		private String privateKey;
+		private @Nullable String privateKey;
 
 		/**
 		 * Password used to decrypt an encrypted private key.
 		 */
-		private String privateKeyPassword;
+		private @Nullable String privateKeyPassword;
 
 		/**
 		 * Whether to verify that the private key matches the public key.
 		 */
 		private boolean verifyKeys;
 
-		public String getType() {
+		public @Nullable String getType() {
 			return this.type;
 		}
 
-		public void setType(String type) {
+		public void setType(@Nullable String type) {
 			this.type = type;
 		}
 
-		public String getCertificate() {
+		public @Nullable String getCertificate() {
 			return this.certificate;
 		}
 
-		public void setCertificate(String certificate) {
+		public void setCertificate(@Nullable String certificate) {
 			this.certificate = certificate;
 		}
 
-		public String getPrivateKey() {
+		public @Nullable String getPrivateKey() {
 			return this.privateKey;
 		}
 
-		public void setPrivateKey(String privateKey) {
+		public void setPrivateKey(@Nullable String privateKey) {
 			this.privateKey = privateKey;
 		}
 
-		public String getPrivateKeyPassword() {
+		public @Nullable String getPrivateKeyPassword() {
 			return this.privateKeyPassword;
 		}
 
-		public void setPrivateKeyPassword(String privateKeyPassword) {
+		public void setPrivateKeyPassword(@Nullable String privateKeyPassword) {
 			this.privateKeyPassword = privateKeyPassword;
 		}
 

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/ssl/PropertiesSslBundle.java

@@ -16,6 +16,12 @@
 
 package org.springframework.boot.autoconfigure.ssl;
 
+import java.security.PrivateKey;
+import java.security.cert.X509Certificate;
+import java.util.List;
+
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.autoconfigure.ssl.SslBundleProperties.Key;
 import org.springframework.boot.io.ApplicationResourceLoader;
 import org.springframework.boot.ssl.SslBundle;
@@ -60,11 +66,11 @@ public final class PropertiesSslBundle implements SslBundle {
 		this.managers = SslManagerBundle.from(this.stores, this.key);
 	}
 
-	private static SslBundleKey asSslKeyReference(Key key) {
+	private static SslBundleKey asSslKeyReference(@Nullable Key key) {
 		return (key != null) ? SslBundleKey.of(key.getPassword(), key.getAlias()) : SslBundleKey.NONE;
 	}
 
-	private static SslOptions asSslOptions(SslBundleProperties.Options options) {
+	private static SslOptions asSslOptions(SslBundleProperties.@Nullable Options options) {
 		return (options != null) ? SslOptions.of(options.getCiphers(), options.getEnabledProtocols()) : SslOptions.NONE;
 	}
 
@@ -120,13 +126,18 @@ public final class PropertiesSslBundle implements SslBundle {
 		return new PropertiesSslBundle(storeBundle, properties);
 	}
 
-	private static PemSslStore getPemSslStore(String propertyName, PemSslBundleProperties.Store properties,
+	private static @Nullable PemSslStore getPemSslStore(String propertyName, PemSslBundleProperties.Store properties,
 			ResourceLoader resourceLoader) {
 		PemSslStoreDetails details = asPemSslStoreDetails(properties);
 		PemSslStore pemSslStore = PemSslStore.load(details, resourceLoader);
 		if (properties.isVerifyKeys()) {
-			CertificateMatcher certificateMatcher = new CertificateMatcher(pemSslStore.privateKey());
-			Assert.state(certificateMatcher.matchesAny(pemSslStore.certificates()),
+			Assert.state(pemSslStore != null, "'pemSslStore' must not be null");
+			PrivateKey privateKey = pemSslStore.privateKey();
+			Assert.state(privateKey != null, "'privateKey' must not be null");
+			CertificateMatcher certificateMatcher = new CertificateMatcher(privateKey);
+			List<X509Certificate> certificates = pemSslStore.certificates();
+			Assert.state(certificates != null, "'certificates' must not be null");
+			Assert.state(certificateMatcher.matchesAny(certificates),
 					() -> "Private key in %s matches none of the certificates in the chain".formatted(propertyName));
 		}
 		return pemSslStore;

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/ssl/SslBundleProperties.java

@@ -18,6 +18,8 @@ package org.springframework.boot.autoconfigure.ssl;
 
 import java.util.Set;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.ssl.SslBundle;
 
 /**
@@ -79,26 +81,26 @@ public abstract class SslBundleProperties {
 		/**
 		 * Supported SSL ciphers.
 		 */
-		private Set<String> ciphers;
+		private @Nullable Set<String> ciphers;
 
 		/**
 		 * Enabled SSL protocols.
 		 */
-		private Set<String> enabledProtocols;
+		private @Nullable Set<String> enabledProtocols;
 
-		public Set<String> getCiphers() {
+		public @Nullable Set<String> getCiphers() {
 			return this.ciphers;
 		}
 
-		public void setCiphers(Set<String> ciphers) {
+		public void setCiphers(@Nullable Set<String> ciphers) {
 			this.ciphers = ciphers;
 		}
 
-		public Set<String> getEnabledProtocols() {
+		public @Nullable Set<String> getEnabledProtocols() {
 			return this.enabledProtocols;
 		}
 
-		public void setEnabledProtocols(Set<String> enabledProtocols) {
+		public void setEnabledProtocols(@Nullable Set<String> enabledProtocols) {
 			this.enabledProtocols = enabledProtocols;
 		}
 
@@ -109,26 +111,26 @@ public abstract class SslBundleProperties {
 		/**
 		 * The password used to access the key in the key store.
 		 */
-		private String password;
+		private @Nullable String password;
 
 		/**
 		 * The alias that identifies the key in the key store.
 		 */
-		private String alias;
+		private @Nullable String alias;
 
-		public String getPassword() {
+		public @Nullable String getPassword() {
 			return this.password;
 		}
 
-		public void setPassword(String password) {
+		public void setPassword(@Nullable String password) {
 			this.password = password;
 		}
 
-		public String getAlias() {
+		public @Nullable String getAlias() {
 			return this.alias;
 		}
 
-		public void setAlias(String alias) {
+		public void setAlias(@Nullable String alias) {
 			this.alias = alias;
 		}
 

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/ssl/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Auto-configuration for SSL bundles.
  */
+@NullMarked
 package org.springframework.boot.autoconfigure.ssl;
+
+import org.jspecify.annotations.NullMarked;

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/task/TaskExecutionProperties.java

@@ -18,6 +18,8 @@ package org.springframework.boot.autoconfigure.task;
 
 import java.time.Duration;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.context.properties.ConfigurationProperties;
 
 /**
@@ -86,7 +88,7 @@ public class TaskExecutionProperties {
 		 * Set the maximum number of parallel accesses allowed. -1 indicates no
 		 * concurrency limit at all.
 		 */
-		private Integer concurrencyLimit;
+		private @Nullable Integer concurrencyLimit;
 
 		public boolean isRejectTasksWhenLimitReached() {
 			return this.rejectTasksWhenLimitReached;
@@ -96,11 +98,11 @@ public class TaskExecutionProperties {
 			this.rejectTasksWhenLimitReached = rejectTasksWhenLimitReached;
 		}
 
-		public Integer getConcurrencyLimit() {
+		public @Nullable Integer getConcurrencyLimit() {
 			return this.concurrencyLimit;
 		}
 
-		public void setConcurrencyLimit(Integer concurrencyLimit) {
+		public void setConcurrencyLimit(@Nullable Integer concurrencyLimit) {
 			this.concurrencyLimit = concurrencyLimit;
 		}
 
@@ -215,7 +217,7 @@ public class TaskExecutionProperties {
 		/**
 		 * Maximum time the executor should wait for remaining tasks to complete.
 		 */
-		private Duration awaitTerminationPeriod;
+		private @Nullable Duration awaitTerminationPeriod;
 
 		public boolean isAwaitTermination() {
 			return this.awaitTermination;
@@ -225,11 +227,11 @@ public class TaskExecutionProperties {
 			this.awaitTermination = awaitTermination;
 		}
 
-		public Duration getAwaitTerminationPeriod() {
+		public @Nullable Duration getAwaitTerminationPeriod() {
 			return this.awaitTerminationPeriod;
 		}
 
-		public void setAwaitTerminationPeriod(Duration awaitTerminationPeriod) {
+		public void setAwaitTerminationPeriod(@Nullable Duration awaitTerminationPeriod) {
 			this.awaitTerminationPeriod = awaitTerminationPeriod;
 		}
 

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/task/TaskExecutorConfigurations.java

@@ -19,6 +19,8 @@ package org.springframework.boot.autoconfigure.task;
 import java.util.List;
 import java.util.concurrent.Executor;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
@@ -54,7 +56,7 @@ import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
  */
 class TaskExecutorConfigurations {
 
-	private static TaskDecorator getTaskDecorator(ObjectProvider<TaskDecorator> taskDecorator) {
+	private static @Nullable TaskDecorator getTaskDecorator(ObjectProvider<TaskDecorator> taskDecorator) {
 		List<TaskDecorator> taskDecorators = taskDecorator.orderedStream().toList();
 		if (taskDecorators.size() == 1) {
 			return taskDecorators.get(0);

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/task/TaskSchedulingConfigurations.java

@@ -19,6 +19,8 @@ package org.springframework.boot.autoconfigure.task;
 import java.util.List;
 import java.util.concurrent.ScheduledExecutorService;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
@@ -45,7 +47,7 @@ import org.springframework.scheduling.config.TaskManagementConfigUtils;
  */
 class TaskSchedulingConfigurations {
 
-	private static TaskDecorator getTaskDecorator(ObjectProvider<TaskDecorator> taskDecorator) {
+	private static @Nullable TaskDecorator getTaskDecorator(ObjectProvider<TaskDecorator> taskDecorator) {
 		List<TaskDecorator> taskDecorators = taskDecorator.orderedStream().toList();
 		if (taskDecorators.size() == 1) {
 			return taskDecorators.get(0);

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/task/TaskSchedulingProperties.java

@@ -18,6 +18,8 @@ package org.springframework.boot.autoconfigure.task;
 
 import java.time.Duration;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.context.properties.ConfigurationProperties;
 
 /**
@@ -84,13 +86,13 @@ public class TaskSchedulingProperties {
 		 * Set the maximum number of parallel accesses allowed. -1 indicates no
 		 * concurrency limit at all.
 		 */
-		private Integer concurrencyLimit;
+		private @Nullable Integer concurrencyLimit;
 
-		public Integer getConcurrencyLimit() {
+		public @Nullable Integer getConcurrencyLimit() {
 			return this.concurrencyLimit;
 		}
 
-		public void setConcurrencyLimit(Integer concurrencyLimit) {
+		public void setConcurrencyLimit(@Nullable Integer concurrencyLimit) {
 			this.concurrencyLimit = concurrencyLimit;
 		}
 
@@ -106,7 +108,7 @@ public class TaskSchedulingProperties {
 		/**
 		 * Maximum time the executor should wait for remaining tasks to complete.
 		 */
-		private Duration awaitTerminationPeriod;
+		private @Nullable Duration awaitTerminationPeriod;
 
 		public boolean isAwaitTermination() {
 			return this.awaitTermination;
@@ -116,11 +118,11 @@ public class TaskSchedulingProperties {
 			this.awaitTermination = awaitTermination;
 		}
 
-		public Duration getAwaitTerminationPeriod() {
+		public @Nullable Duration getAwaitTerminationPeriod() {
 			return this.awaitTerminationPeriod;
 		}
 
-		public void setAwaitTerminationPeriod(Duration awaitTerminationPeriod) {
+		public void setAwaitTerminationPeriod(@Nullable Duration awaitTerminationPeriod) {
 			this.awaitTerminationPeriod = awaitTerminationPeriod;
 		}
 

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/task/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Auto-configuration for task execution and scheduling.
  */
+@NullMarked
 package org.springframework.boot.autoconfigure.task;
+
+import org.jspecify.annotations.NullMarked;

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/template/TemplateAvailabilityProviders.java

@@ -23,6 +23,8 @@ import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.context.ApplicationContext;
 import org.springframework.core.env.Environment;
 import org.springframework.core.io.ResourceLoader;
@@ -72,7 +74,14 @@ public class TemplateAvailabilityProviders {
 	 * @param applicationContext the source application context
 	 */
 	public TemplateAvailabilityProviders(ApplicationContext applicationContext) {
-		this((applicationContext != null) ? applicationContext.getClassLoader() : null);
+		this(getClassLoader(applicationContext));
+	}
+
+	private static ClassLoader getClassLoader(ApplicationContext applicationContext) {
+		Assert.notNull(applicationContext, "'applicationContext' must not be null");
+		ClassLoader classLoader = applicationContext.getClassLoader();
+		Assert.state(classLoader != null, "'classLoader' must not be null");
+		return classLoader;
 	}
 
 	/**
@@ -107,10 +116,11 @@ public class TemplateAvailabilityProviders {
 	 * @param applicationContext the application context
 	 * @return a {@link TemplateAvailabilityProvider} or null
 	 */
-	public TemplateAvailabilityProvider getProvider(String view, ApplicationContext applicationContext) {
+	public @Nullable TemplateAvailabilityProvider getProvider(String view, ApplicationContext applicationContext) {
 		Assert.notNull(applicationContext, "'applicationContext' must not be null");
-		return getProvider(view, applicationContext.getEnvironment(), applicationContext.getClassLoader(),
-				applicationContext);
+		ClassLoader classLoader = applicationContext.getClassLoader();
+		Assert.state(classLoader != null, "'classLoader' must not be null");
+		return getProvider(view, applicationContext.getEnvironment(), classLoader, applicationContext);
 	}
 
 	/**
@@ -121,8 +131,8 @@ public class TemplateAvailabilityProviders {
 	 * @param resourceLoader the resource loader
 	 * @return a {@link TemplateAvailabilityProvider} or null
 	 */
-	public TemplateAvailabilityProvider getProvider(String view, Environment environment, ClassLoader classLoader,
-			ResourceLoader resourceLoader) {
+	public @Nullable TemplateAvailabilityProvider getProvider(String view, Environment environment,
+			ClassLoader classLoader, ResourceLoader resourceLoader) {
 		Assert.notNull(view, "'view' must not be null");
 		Assert.notNull(environment, "'environment' must not be null");
 		Assert.notNull(classLoader, "'classLoader' must not be null");
@@ -143,8 +153,8 @@ public class TemplateAvailabilityProviders {
 		return (provider != NONE) ? provider : null;
 	}
 
-	private TemplateAvailabilityProvider findProvider(String view, Environment environment, ClassLoader classLoader,
-			ResourceLoader resourceLoader) {
+	private @Nullable TemplateAvailabilityProvider findProvider(String view, Environment environment,
+			ClassLoader classLoader, ResourceLoader resourceLoader) {
 		for (TemplateAvailabilityProvider candidate : this.providers) {
 			if (candidate.isTemplateAvailable(view, environment, classLoader, resourceLoader)) {
 				return candidate;

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/template/TemplateRuntimeHints.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.autoconfigure.template;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.aot.hint.RuntimeHints;
 import org.springframework.aot.hint.RuntimeHintsRegistrar;
 
@@ -27,7 +29,7 @@ import org.springframework.aot.hint.RuntimeHintsRegistrar;
 class TemplateRuntimeHints implements RuntimeHintsRegistrar {
 
 	@Override
-	public void registerHints(RuntimeHints hints, ClassLoader classLoader) {
+	public void registerHints(RuntimeHints hints, @Nullable ClassLoader classLoader) {
 		hints.resources().registerPatternIfPresent(classLoader, "templates", (hint) -> hint.includes("templates/**"));
 	}
 

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/template/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Base classes for template Auto-configuration.
  */
+@NullMarked
 package org.springframework.boot.autoconfigure.template;
+
+import org.jspecify.annotations.NullMarked;

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/OnEnabledResourceChainCondition.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.autoconfigure.web;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.autoconfigure.condition.ConditionMessage;
 import org.springframework.boot.autoconfigure.condition.ConditionOutcome;
 import org.springframework.boot.autoconfigure.condition.SpringBootCondition;
@@ -24,6 +26,7 @@ import org.springframework.context.annotation.Condition;
 import org.springframework.context.annotation.ConditionContext;
 import org.springframework.core.env.ConfigurableEnvironment;
 import org.springframework.core.type.AnnotatedTypeMetadata;
+import org.springframework.lang.Contract;
 import org.springframework.util.ClassUtils;
 
 /**
@@ -64,8 +67,13 @@ class OnEnabledResourceChainCondition extends SpringBootCondition {
 		return ConditionOutcome.noMatch(message.because("disabled"));
 	}
 
-	private Boolean getEnabledProperty(ConfigurableEnvironment environment, String key, Boolean defaultValue) {
+	@Contract("_, _, !null -> !null")
+	private @Nullable Boolean getEnabledProperty(ConfigurableEnvironment environment, String key,
+			@Nullable Boolean defaultValue) {
 		String name = "spring.web.resources.chain." + key + "enabled";
+		if (defaultValue == null) {
+			return environment.getProperty(name, Boolean.class);
+		}
 		return environment.getProperty(name, Boolean.class, defaultValue);
 	}
 

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/WebProperties.java

@@ -21,6 +21,8 @@ import java.time.temporal.ChronoUnit;
 import java.util.Locale;
 import java.util.concurrent.TimeUnit;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.context.properties.ConfigurationProperties;
 import org.springframework.boot.context.properties.PropertyMapper;
 import org.springframework.boot.convert.DurationUnit;
@@ -39,7 +41,7 @@ public class WebProperties {
 	 * Locale to use. By default, this locale is overridden by the "Accept-Language"
 	 * header.
 	 */
-	private Locale locale;
+	private @Nullable Locale locale;
 
 	/**
 	 * Define how the locale should be resolved.
@@ -48,11 +50,11 @@ public class WebProperties {
 
 	private final Resources resources = new Resources();
 
-	public Locale getLocale() {
+	public @Nullable Locale getLocale() {
 		return this.locale;
 	}
 
-	public void setLocale(Locale locale) {
+	public void setLocale(@Nullable Locale locale) {
 		this.locale = locale;
 	}
 
@@ -155,7 +157,7 @@ public class WebProperties {
 			 * Whether to enable the Spring Resource Handling chain. By default, disabled
 			 * unless at least one strategy has been enabled.
 			 */
-			private Boolean enabled;
+			private @Nullable Boolean enabled;
 
 			/**
 			 * Whether to enable caching in the Resource chain.
@@ -177,7 +179,7 @@ public class WebProperties {
 			 * @return whether the resource chain is enabled or {@code null} if no
 			 * specified settings are present.
 			 */
-			public Boolean getEnabled() {
+			public @Nullable Boolean getEnabled() {
 				return getEnabled(getStrategy().getFixed().isEnabled(), getStrategy().getContent().isEnabled(),
 						this.enabled);
 			}
@@ -213,7 +215,8 @@ public class WebProperties {
 				this.customized = true;
 			}
 
-			static Boolean getEnabled(boolean fixedEnabled, boolean contentEnabled, Boolean chainEnabled) {
+			static @Nullable Boolean getEnabled(boolean fixedEnabled, boolean contentEnabled,
+					@Nullable Boolean chainEnabled) {
 				return (fixedEnabled || contentEnabled) ? Boolean.TRUE : chainEnabled;
 			}
 
@@ -299,7 +302,7 @@ public class WebProperties {
 					/**
 					 * Version string to use for the fixed Version Strategy.
 					 */
-					private String version;
+					private @Nullable String version;
 
 					public boolean isEnabled() {
 						return this.enabled;
@@ -319,11 +322,11 @@ public class WebProperties {
 						this.paths = paths;
 					}
 
-					public String getVersion() {
+					public @Nullable String getVersion() {
 						return this.version;
 					}
 
-					public void setVersion(String version) {
+					public void setVersion(@Nullable String version) {
 						this.customized = true;
 						this.version = version;
 					}
@@ -351,7 +354,7 @@ public class WebProperties {
 			 * by the 'spring.web.resources.cache.cachecontrol' properties.
 			 */
 			@DurationUnit(ChronoUnit.SECONDS)
-			private Duration period;
+			private @Nullable Duration period;
 
 			/**
 			 * Cache control HTTP headers, only allows valid directive combinations.
@@ -365,11 +368,11 @@ public class WebProperties {
 			 */
 			private boolean useLastModified = true;
 
-			public Duration getPeriod() {
+			public @Nullable Duration getPeriod() {
 				return this.period;
 			}
 
-			public void setPeriod(Duration period) {
+			public void setPeriod(@Nullable Duration period) {
 				this.customized = true;
 				this.period = period;
 			}
@@ -402,169 +405,169 @@ public class WebProperties {
 				 * suffix is not specified.
 				 */
 				@DurationUnit(ChronoUnit.SECONDS)
-				private Duration maxAge;
+				private @Nullable Duration maxAge;
 
 				/**
 				 * Indicate that the cached response can be reused only if re-validated
 				 * with the server.
 				 */
-				private Boolean noCache;
+				private @Nullable Boolean noCache;
 
 				/**
 				 * Indicate to not cache the response in any case.
 				 */
-				private Boolean noStore;
+				private @Nullable Boolean noStore;
 
 				/**
 				 * Indicate that once it has become stale, a cache must not use the
 				 * response without re-validating it with the server.
 				 */
-				private Boolean mustRevalidate;
+				private @Nullable Boolean mustRevalidate;
 
 				/**
 				 * Indicate intermediaries (caches and others) that they should not
 				 * transform the response content.
 				 */
-				private Boolean noTransform;
+				private @Nullable Boolean noTransform;
 
 				/**
 				 * Indicate that any cache may store the response.
 				 */
-				private Boolean cachePublic;
+				private @Nullable Boolean cachePublic;
 
 				/**
 				 * Indicate that the response message is intended for a single user and
 				 * must not be stored by a shared cache.
 				 */
-				private Boolean cachePrivate;
+				private @Nullable Boolean cachePrivate;
 
 				/**
 				 * Same meaning as the "must-revalidate" directive, except that it does
 				 * not apply to private caches.
 				 */
-				private Boolean proxyRevalidate;
+				private @Nullable Boolean proxyRevalidate;
 
 				/**
 				 * Maximum time the response can be served after it becomes stale, in
 				 * seconds if no duration suffix is not specified.
 				 */
 				@DurationUnit(ChronoUnit.SECONDS)
-				private Duration staleWhileRevalidate;
+				private @Nullable Duration staleWhileRevalidate;
 
 				/**
 				 * Maximum time the response may be used when errors are encountered, in
 				 * seconds if no duration suffix is not specified.
 				 */
 				@DurationUnit(ChronoUnit.SECONDS)
-				private Duration staleIfError;
+				private @Nullable Duration staleIfError;
 
 				/**
 				 * Maximum time the response should be cached by shared caches, in seconds
 				 * if no duration suffix is not specified.
 				 */
 				@DurationUnit(ChronoUnit.SECONDS)
-				private Duration sMaxAge;
+				private @Nullable Duration sMaxAge;
 
-				public Duration getMaxAge() {
+				public @Nullable Duration getMaxAge() {
 					return this.maxAge;
 				}
 
-				public void setMaxAge(Duration maxAge) {
+				public void setMaxAge(@Nullable Duration maxAge) {
 					this.customized = true;
 					this.maxAge = maxAge;
 				}
 
-				public Boolean getNoCache() {
+				public @Nullable Boolean getNoCache() {
 					return this.noCache;
 				}
 
-				public void setNoCache(Boolean noCache) {
+				public void setNoCache(@Nullable Boolean noCache) {
 					this.customized = true;
 					this.noCache = noCache;
 				}
 
-				public Boolean getNoStore() {
+				public @Nullable Boolean getNoStore() {
 					return this.noStore;
 				}
 
-				public void setNoStore(Boolean noStore) {
+				public void setNoStore(@Nullable Boolean noStore) {
 					this.customized = true;
 					this.noStore = noStore;
 				}
 
-				public Boolean getMustRevalidate() {
+				public @Nullable Boolean getMustRevalidate() {
 					return this.mustRevalidate;
 				}
 
-				public void setMustRevalidate(Boolean mustRevalidate) {
+				public void setMustRevalidate(@Nullable Boolean mustRevalidate) {
 					this.customized = true;
 					this.mustRevalidate = mustRevalidate;
 				}
 
-				public Boolean getNoTransform() {
+				public @Nullable Boolean getNoTransform() {
 					return this.noTransform;
 				}
 
-				public void setNoTransform(Boolean noTransform) {
+				public void setNoTransform(@Nullable Boolean noTransform) {
 					this.customized = true;
 					this.noTransform = noTransform;
 				}
 
-				public Boolean getCachePublic() {
+				public @Nullable Boolean getCachePublic() {
 					return this.cachePublic;
 				}
 
-				public void setCachePublic(Boolean cachePublic) {
+				public void setCachePublic(@Nullable Boolean cachePublic) {
 					this.customized = true;
 					this.cachePublic = cachePublic;
 				}
 
-				public Boolean getCachePrivate() {
+				public @Nullable Boolean getCachePrivate() {
 					return this.cachePrivate;
 				}
 
-				public void setCachePrivate(Boolean cachePrivate) {
+				public void setCachePrivate(@Nullable Boolean cachePrivate) {
 					this.customized = true;
 					this.cachePrivate = cachePrivate;
 				}
 
-				public Boolean getProxyRevalidate() {
+				public @Nullable Boolean getProxyRevalidate() {
 					return this.proxyRevalidate;
 				}
 
-				public void setProxyRevalidate(Boolean proxyRevalidate) {
+				public void setProxyRevalidate(@Nullable Boolean proxyRevalidate) {
 					this.customized = true;
 					this.proxyRevalidate = proxyRevalidate;
 				}
 
-				public Duration getStaleWhileRevalidate() {
+				public @Nullable Duration getStaleWhileRevalidate() {
 					return this.staleWhileRevalidate;
 				}
 
-				public void setStaleWhileRevalidate(Duration staleWhileRevalidate) {
+				public void setStaleWhileRevalidate(@Nullable Duration staleWhileRevalidate) {
 					this.customized = true;
 					this.staleWhileRevalidate = staleWhileRevalidate;
 				}
 
-				public Duration getStaleIfError() {
+				public @Nullable Duration getStaleIfError() {
 					return this.staleIfError;
 				}
 
-				public void setStaleIfError(Duration staleIfError) {
+				public void setStaleIfError(@Nullable Duration staleIfError) {
 					this.customized = true;
 					this.staleIfError = staleIfError;
 				}
 
-				public Duration getSMaxAge() {
+				public @Nullable Duration getSMaxAge() {
 					return this.sMaxAge;
 				}
 
-				public void setSMaxAge(Duration sMaxAge) {
+				public void setSMaxAge(@Nullable Duration sMaxAge) {
 					this.customized = true;
 					this.sMaxAge = sMaxAge;
 				}
 
-				public CacheControl toHttpCacheControl() {
+				public @Nullable CacheControl toHttpCacheControl() {
 					PropertyMapper map = PropertyMapper.get();
 					CacheControl control = createCacheControl();
 					map.from(this::getMustRevalidate).whenTrue().toCall(control::mustRevalidate);

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/WebResourcesRuntimeHints.java

@@ -18,6 +18,8 @@ package org.springframework.boot.autoconfigure.web;
 
 import java.util.List;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.aot.hint.RuntimeHints;
 import org.springframework.aot.hint.RuntimeHintsRegistrar;
 
@@ -33,7 +35,7 @@ public class WebResourcesRuntimeHints implements RuntimeHintsRegistrar {
 			"public/");
 
 	@Override
-	public void registerHints(RuntimeHints hints, ClassLoader classLoader) {
+	public void registerHints(RuntimeHints hints, @Nullable ClassLoader classLoader) {
 		ClassLoader classLoaderToUse = (classLoader != null) ? classLoader : getClass().getClassLoader();
 		String[] locations = DEFAULT_LOCATIONS.stream()
 			.filter((candidate) -> classLoaderToUse.getResource(candidate) != null)

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/format/DateTimeFormatters.java

@@ -19,6 +19,8 @@ package org.springframework.boot.autoconfigure.web.format;
 import java.time.format.DateTimeFormatter;
 import java.time.format.ResolverStyle;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.util.StringUtils;
 
 /**
@@ -30,13 +32,13 @@ import org.springframework.util.StringUtils;
  */
 public class DateTimeFormatters {
 
-	private DateTimeFormatter dateFormatter;
+	private @Nullable DateTimeFormatter dateFormatter;
 
-	private String datePattern;
+	private @Nullable String datePattern;
 
-	private DateTimeFormatter timeFormatter;
+	private @Nullable DateTimeFormatter timeFormatter;
 
-	private DateTimeFormatter dateTimeFormatter;
+	private @Nullable DateTimeFormatter dateTimeFormatter;
 
 	/**
 	 * Configures the date format using the given {@code pattern}.
@@ -77,19 +79,19 @@ public class DateTimeFormatters {
 		return this;
 	}
 
-	DateTimeFormatter getDateFormatter() {
+	@Nullable DateTimeFormatter getDateFormatter() {
 		return this.dateFormatter;
 	}
 
-	String getDatePattern() {
+	@Nullable String getDatePattern() {
 		return this.datePattern;
 	}
 
-	DateTimeFormatter getTimeFormatter() {
+	@Nullable DateTimeFormatter getTimeFormatter() {
 		return this.timeFormatter;
 	}
 
-	DateTimeFormatter getDateTimeFormatter() {
+	@Nullable DateTimeFormatter getDateTimeFormatter() {
 		return this.dateTimeFormatter;
 	}
 
@@ -97,7 +99,7 @@ public class DateTimeFormatters {
 		return this.dateFormatter != null || this.timeFormatter != null || this.dateTimeFormatter != null;
 	}
 
-	private static DateTimeFormatter formatter(String pattern) {
+	private static @Nullable DateTimeFormatter formatter(String pattern) {
 		return StringUtils.hasText(pattern)
 				? DateTimeFormatter.ofPattern(pattern).withResolverStyle(ResolverStyle.SMART) : null;
 	}

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/format/WebConversionService.java

@@ -20,6 +20,8 @@ import java.time.format.DateTimeFormatter;
 import java.util.function.Consumer;
 import java.util.function.Supplier;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.format.datetime.DateFormatter;
 import org.springframework.format.datetime.DateFormatterRegistrar;
 import org.springframework.format.datetime.standard.DateTimeFormatterRegistrar;
@@ -79,7 +81,7 @@ public class WebConversionService extends DefaultFormattingConversionService {
 		dateTime.registerFormatters(this);
 	}
 
-	private void configure(Supplier<DateTimeFormatter> supplier, Consumer<DateTimeFormatter> consumer) {
+	private void configure(Supplier<@Nullable DateTimeFormatter> supplier, Consumer<DateTimeFormatter> consumer) {
 		DateTimeFormatter formatter = supplier.get();
 		if (formatter != null) {
 			consumer.accept(formatter);

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/format/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Support classes for web-specific formatting.
  */
+@NullMarked
 package org.springframework.boot.autoconfigure.web.format;
+
+import org.jspecify.annotations.NullMarked;

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Auto-configuration for common web concerns.
  */
+@NullMarked
 package org.springframework.boot.autoconfigure.web;
+
+import org.jspecify.annotations.NullMarked;

core/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/template/TemplateAvailabilityProvidersTests.java

@@ -73,7 +73,7 @@ class TemplateAvailabilityProvidersTests {
 	void createWhenApplicationContextIsNullShouldThrowException() {
 		assertThatIllegalArgumentException()
 			.isThrownBy(() -> new TemplateAvailabilityProviders((ApplicationContext) null))
-			.withMessageContaining("'classLoader' must not be null");
+			.withMessageContaining("'applicationContext' must not be null");
 	}
 
 	@Test