Improve null-safety of build-plugin/spring-boot-gradle-plugin

See gh-46926

build-plugin/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/plugin/ApplicationPluginAction.java

@@ -17,6 +17,7 @@
 package org.springframework.boot.gradle.plugin;
 
 import java.io.IOException;
+import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.io.StringWriter;
 import java.util.concurrent.Callable;
@@ -38,6 +39,7 @@ import org.gradle.jvm.application.scripts.TemplateBasedScriptGenerator;
 import org.gradle.util.GradleVersion;
 
 import org.springframework.boot.gradle.tasks.run.BootRun;
+import org.springframework.util.Assert;
 
 /**
  * Action that is executed in response to the {@link ApplicationPlugin} being applied.
@@ -110,7 +112,7 @@ final class ApplicationPluginAction implements PluginApplicationAction {
 	}
 
 	private String loadResource(String name) {
-		try (InputStreamReader reader = new InputStreamReader(getClass().getResourceAsStream(name))) {
+		try (InputStreamReader reader = new InputStreamReader(getResourceAsStream(name))) {
 			char[] buffer = new char[4096];
 			int read;
 			StringWriter writer = new StringWriter();
@@ -124,6 +126,12 @@ final class ApplicationPluginAction implements PluginApplicationAction {
 		}
 	}
 
+	private InputStream getResourceAsStream(String name) {
+		InputStream stream = getClass().getResourceAsStream(name);
+		Assert.state(stream != null, "Resource '%s' not found'".formatted(name));
+		return stream;
+	}
+
 	private void configureFilePermissions(CopySpec copySpec, int mode) {
 		if (GradleVersion.current().compareTo(GradleVersion.version("8.3")) >= 0) {
 			copySpec.filePermissions((filePermissions) -> filePermissions.unix(Integer.toString(mode, 8)));

build-plugin/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/tasks/buildinfo/BuildInfoProperties.java

@@ -48,7 +48,7 @@ public abstract class BuildInfoProperties implements Serializable {
 
 	private final SetProperty<String> excludes;
 
-	private final Supplier<String> creationTime = () -> DateTimeFormatter.ISO_INSTANT.format(Instant.now());
+	private final Supplier<@Nullable String> creationTime = () -> DateTimeFormatter.ISO_INSTANT.format(Instant.now());
 
 	@Inject
 	public BuildInfoProperties(Project project, SetProperty<String> excludes) {
@@ -142,15 +142,19 @@ public abstract class BuildInfoProperties implements Serializable {
 		return coerceToStringValues(applyExclusions(getAdditional().getOrElse(Collections.emptyMap())));
 	}
 
+	@SuppressWarnings("NullAway") // Doesn't detect lambda with correct nullability
 	private <T> @Nullable T getIfNotExcluded(Property<T> property, String name) {
 		return getIfNotExcluded(property, name, () -> null);
 	}
 
-	private <T> @Nullable T getIfNotExcluded(Property<T> property, String name, Supplier<T> defaultValue) {
+	private <T> @Nullable T getIfNotExcluded(Property<T> property, String name, Supplier<@Nullable T> defaultValue) {
 		if (this.excludes.getOrElse(Collections.emptySet()).contains(name)) {
 			return null;
 		}
-		return property.getOrElse(defaultValue.get());
+		if (property.isPresent()) {
+			return property.get();
+		}
+		return defaultValue.get();
 	}
 
 	private Map<String, String> coerceToStringValues(Map<String, Object> input) {
@@ -159,7 +163,9 @@ public abstract class BuildInfoProperties implements Serializable {
 			if (value instanceof Provider<?> provider) {
 				value = provider.getOrNull();
 			}
-			output.put(key, (value != null) ? value.toString() : null);
+			if (value != null) {
+				output.put(key, value.toString());
+			}
 		});
 		return output;
 	}
@@ -167,7 +173,12 @@ public abstract class BuildInfoProperties implements Serializable {
 	private Map<String, Object> applyExclusions(Map<String, Object> input) {
 		Map<String, Object> output = new HashMap<>();
 		Set<String> exclusions = this.excludes.getOrElse(Collections.emptySet());
-		input.forEach((key, value) -> output.put(key, (!exclusions.contains(key)) ? value : null));
+		input.forEach((key, value) -> {
+			boolean isExcluded = exclusions.contains(key);
+			if (!isExcluded) {
+				output.put(key, value);
+			}
+		});
 		return output;
 	}
 

build-plugin/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/tasks/bundling/BootBuildImage.java

@@ -41,6 +41,7 @@ import org.gradle.work.DisableCachingByDefault;
 import org.springframework.boot.buildpack.platform.build.BuildRequest;
 import org.springframework.boot.buildpack.platform.build.Builder;
 import org.springframework.boot.buildpack.platform.build.BuildpackReference;
+import org.springframework.boot.buildpack.platform.build.Cache;
 import org.springframework.boot.buildpack.platform.build.Creator;
 import org.springframework.boot.buildpack.platform.build.PullPolicy;
 import org.springframework.boot.buildpack.platform.docker.transport.DockerEngineException;
@@ -460,14 +461,17 @@ public abstract class BootBuildImage extends DefaultTask {
 	}
 
 	private BuildRequest customizeCaches(BuildRequest request) {
-		if (this.buildWorkspace.asCache() != null) {
-			request = request.withBuildWorkspace((this.buildWorkspace.asCache()));
+		Cache buildWorkspaceCache = this.buildWorkspace.asCache();
+		if (buildWorkspaceCache != null) {
+			request = request.withBuildWorkspace(buildWorkspaceCache);
 		}
-		if (this.buildCache.asCache() != null) {
-			request = request.withBuildCache(this.buildCache.asCache());
+		Cache buildCache = this.buildCache.asCache();
+		if (buildCache != null) {
+			request = request.withBuildCache(buildCache);
 		}
-		if (this.launchCache.asCache() != null) {
-			request = request.withLaunchCache(this.launchCache.asCache());
+		Cache launchCache = this.launchCache.asCache();
+		if (launchCache != null) {
+			request = request.withLaunchCache(launchCache);
 		}
 		return request;
 	}

build-plugin/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/tasks/bundling/BootZipCopyAction.java

@@ -22,6 +22,7 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.io.OutputStreamWriter;
+import java.nio.charset.StandardCharsets;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
 import java.time.OffsetDateTime;
@@ -111,7 +112,7 @@ class BootZipCopyAction implements CopyAction {
 
 	private final Function<FileCopyDetails, ZipCompression> compressionResolver;
 
-	private final String encoding;
+	private final @Nullable String encoding;
 
 	private final ResolvedDependencies resolvedDependencies;
 
@@ -125,7 +126,7 @@ class BootZipCopyAction implements CopyAction {
 			@Nullable Integer fileMode, boolean includeDefaultLoader, @Nullable String jarmodeToolsLocation,
 			Spec<FileTreeElement> requiresUnpack, Spec<FileTreeElement> exclusions,
 			@Nullable LaunchScriptConfiguration launchScript, Spec<FileCopyDetails> librarySpec,
-			Function<FileCopyDetails, ZipCompression> compressionResolver, String encoding,
+			Function<FileCopyDetails, ZipCompression> compressionResolver, @Nullable String encoding,
 			ResolvedDependencies resolvedDependencies, boolean supportsSignatureFile,
 			@Nullable LayerResolver layerResolver, LoaderImplementation loaderImplementation) {
 		this.output = output;
@@ -390,7 +391,8 @@ class BootZipCopyAction implements CopyAction {
 			if (classPathIndex != null) {
 				Set<String> libraryNames = this.writtenLibraries.keySet();
 				List<String> lines = libraryNames.stream().map((line) -> "- \"" + line + "\"").toList();
-				ZipEntryContentWriter writer = ZipEntryContentWriter.fromLines(BootZipCopyAction.this.encoding, lines);
+				ZipEntryContentWriter writer = ZipEntryContentWriter.fromLines((BootZipCopyAction.this.encoding != null)
+						? BootZipCopyAction.this.encoding : StandardCharsets.UTF_8.name(), lines);
 				writeEntry(classPathIndex, writer, true);
 			}
 		}
@@ -415,7 +417,8 @@ class BootZipCopyAction implements CopyAction {
 			}
 			NativeImageArgFile argFile = new NativeImageArgFile(excludes);
 			argFile.writeIfNecessary((lines) -> {
-				ZipEntryContentWriter writer = ZipEntryContentWriter.fromLines(BootZipCopyAction.this.encoding, lines);
+				ZipEntryContentWriter writer = ZipEntryContentWriter.fromLines((BootZipCopyAction.this.encoding != null)
+						? BootZipCopyAction.this.encoding : StandardCharsets.UTF_8.name(), lines);
 				writeEntry(NativeImageArgFile.LOCATION, writer, true);
 			});
 		}

build-plugin/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/tasks/bundling/LoaderZipEntries.java

@@ -30,6 +30,7 @@ import org.gradle.api.file.FileTreeElement;
 import org.jspecify.annotations.Nullable;
 
 import org.springframework.boot.loader.tools.LoaderImplementation;
+import org.springframework.util.Assert;
 import org.springframework.util.StreamUtils;
 
 /**
@@ -61,7 +62,7 @@ class LoaderZipEntries {
 	WrittenEntries writeTo(ZipArchiveOutputStream out) throws IOException {
 		WrittenEntries written = new WrittenEntries();
 		try (ZipInputStream loaderJar = new ZipInputStream(
-				getClass().getResourceAsStream("/" + this.loaderImplementation.getJarResourceName()))) {
+				getResourceAsStream("/" + this.loaderImplementation.getJarResourceName()))) {
 			java.util.zip.ZipEntry entry = loaderJar.getNextEntry();
 			while (entry != null) {
 				if (entry.isDirectory() && !entry.getName().equals("META-INF/")) {
@@ -78,6 +79,12 @@ class LoaderZipEntries {
 		return written;
 	}
 
+	private InputStream getResourceAsStream(String name) {
+		InputStream stream = getClass().getResourceAsStream(name);
+		Assert.state(stream != null, "Resource '%s not found'".formatted(name));
+		return stream;
+	}
+
 	private void writeDirectory(ZipArchiveEntry entry, ZipArchiveOutputStream out) throws IOException {
 		prepareEntry(entry, this.dirMode);
 		out.putArchiveEntry(entry);