Improve null-safety of module/spring-boot-actuator-autoconfigure

See gh-46926

module/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/availability/AvailabilityProbesHealthEndpointGroups.java

@@ -122,7 +122,11 @@ class AvailabilityProbesHealthEndpointGroups implements HealthEndpointGroups, Ad
 		}
 		List<String> additionalPaths = new ArrayList<>();
 		if (this.groups instanceof AdditionalPathsMapper additionalPathsMapper) {
-			additionalPaths.addAll(additionalPathsMapper.getAdditionalPaths(endpointId, webServerNamespace));
+			List<String> mappedAdditionalPaths = getAdditionalPaths(endpointId, webServerNamespace,
+					additionalPathsMapper);
+			if (mappedAdditionalPaths != null) {
+				additionalPaths.addAll(mappedAdditionalPaths);
+			}
 		}
 		additionalPaths.addAll(this.probeGroups.values()
 			.stream()
@@ -134,4 +138,9 @@ class AvailabilityProbesHealthEndpointGroups implements HealthEndpointGroups, Ad
 		return additionalPaths;
 	}
 
+	private static @Nullable List<String> getAdditionalPaths(EndpointId endpointId,
+			WebServerNamespace webServerNamespace, AdditionalPathsMapper additionalPathsMapper) {
+		return additionalPathsMapper.getAdditionalPaths(endpointId, webServerNamespace);
+	}
+
 }

module/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/condition/ConditionsReportEndpoint.java

@@ -63,7 +63,7 @@ public class ConditionsReportEndpoint {
 
 	@ReadOperation
 	public ConditionsDescriptor conditions() {
-		Map<String, ContextConditionsDescriptor> contextConditionEvaluations = new HashMap<>();
+		Map<@Nullable String, ContextConditionsDescriptor> contextConditionEvaluations = new HashMap<>();
 		ConfigurableApplicationContext target = this.context;
 		while (target != null) {
 			contextConditionEvaluations.put(target.getId(), new ContextConditionsDescriptor(target));
@@ -85,13 +85,13 @@ public class ConditionsReportEndpoint {
 	 */
 	public static final class ConditionsDescriptor implements OperationResponseBody {
 
-		private final Map<String, ContextConditionsDescriptor> contexts;
+		private final Map<@Nullable String, ContextConditionsDescriptor> contexts;
 
-		private ConditionsDescriptor(Map<String, ContextConditionsDescriptor> contexts) {
+		private ConditionsDescriptor(Map<@Nullable String, ContextConditionsDescriptor> contexts) {
 			this.contexts = contexts;
 		}
 
-		public Map<String, ContextConditionsDescriptor> getContexts() {
+		public Map<@Nullable String, ContextConditionsDescriptor> getContexts() {
 			return this.contexts;
 		}
 

module/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/web/server/AccessLogCustomizer.java

@@ -21,6 +21,7 @@ import org.jspecify.annotations.Nullable;
 import org.springframework.boot.web.server.WebServerFactory;
 import org.springframework.boot.web.server.WebServerFactoryCustomizer;
 import org.springframework.core.Ordered;
+import org.springframework.lang.Contract;
 
 /**
  * Base class for a {@link WebServerFactoryCustomizer} that customizes the web server's
@@ -39,6 +40,7 @@ public abstract class AccessLogCustomizer<T extends WebServerFactory>
 		this.prefix = prefix;
 	}
 
+	@Contract("!null -> !null")
 	protected @Nullable String customizePrefix(@Nullable String existingPrefix) {
 		if (this.prefix == null) {
 			return existingPrefix;

module/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/web/server/ChildManagementContextInitializer.java

@@ -85,32 +85,35 @@ class ChildManagementContextInitializer implements BeanRegistrationAotProcessor,
 		if (!(this.parentContext instanceof WebServerApplicationContext)) {
 			return;
 		}
-		if (this.managementContext == null) {
+		ConfigurableApplicationContext managementContext = this.managementContext;
-			ConfigurableApplicationContext managementContext = createManagementContext();
+		if (managementContext == null) {
+			managementContext = createManagementContext();
 			registerBeans(managementContext);
 			managementContext.refresh();
 			this.managementContext = managementContext;
 		}
 		else {
-			this.managementContext.start();
+			managementContext.start();
 		}
 	}
 
 	@Override
 	public void stop() {
-		if (this.managementContext != null) {
+		ConfigurableApplicationContext managementContext = this.managementContext;
+		if (managementContext != null) {
 			if (this.parentContext.isClosed()) {
-				this.managementContext.close();
+				managementContext.close();
 			}
 			else {
-				this.managementContext.stop();
+				managementContext.stop();
 			}
 		}
 	}
 
 	@Override
 	public boolean isRunning() {
-		return this.managementContext != null && this.managementContext.isRunning();
+		ConfigurableApplicationContext managementContext = this.managementContext;
+		return managementContext != null && managementContext.isRunning();
 	}
 
 	@Override