Improve null-safety of buildpack/spring-boot-buildpack-platform

See gh-47263

buildpack/spring-boot-buildpack-platform/src/main/java/org/springframework/boot/buildpack/platform/build/BuilderException.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.buildpack.platform.build;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.util.StringUtils;
 
 /**
@@ -26,11 +28,11 @@ import org.springframework.util.StringUtils;
  */
 public class BuilderException extends RuntimeException {
 
-	private final String operation;
+	private final @Nullable String operation;
 
 	private final int statusCode;
 
-	BuilderException(String operation, int statusCode) {
+	BuilderException(@Nullable String operation, int statusCode) {
 		super(buildMessage(operation, statusCode));
 		this.operation = operation;
 		this.statusCode = statusCode;
@@ -40,7 +42,7 @@ public class BuilderException extends RuntimeException {
 	 * Return the Builder operation that failed.
 	 * @return the operation description
 	 */
-	public String getOperation() {
+	public @Nullable String getOperation() {
 		return this.operation;
 	}
 
@@ -52,7 +54,7 @@ public class BuilderException extends RuntimeException {
 		return this.statusCode;
 	}
 
-	private static String buildMessage(String operation, int statusCode) {
+	private static String buildMessage(@Nullable String operation, int statusCode) {
 		StringBuilder message = new StringBuilder("Builder");
 		if (StringUtils.hasLength(operation)) {
 			message.append(" lifecycle '").append(operation).append("'");

buildpack/spring-boot-buildpack-platform/src/main/java/org/springframework/boot/buildpack/platform/build/BuildpackCoordinates.java

@@ -134,7 +134,7 @@ final class BuildpackCoordinates {
 	 * @param version the buildpack version
 	 * @return a new {@link BuildpackCoordinates} instance
 	 */
-	static BuildpackCoordinates of(String id, String version) {
+	static BuildpackCoordinates of(String id, @Nullable String version) {
 		return new BuildpackCoordinates(id, version);
 	}
 

buildpack/spring-boot-buildpack-platform/src/main/java/org/springframework/boot/buildpack/platform/build/Buildpacks.java

@@ -20,6 +20,8 @@ import java.io.IOException;
 import java.util.Collections;
 import java.util.List;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.buildpack.platform.docker.type.Layer;
 import org.springframework.boot.buildpack.platform.io.Content;
 import org.springframework.boot.buildpack.platform.io.IOConsumer;
@@ -79,7 +81,7 @@ final class Buildpacks {
 		builder.append("\n");
 	}
 
-	static Buildpacks of(List<Buildpack> buildpacks) {
+	static Buildpacks of(@Nullable List<Buildpack> buildpacks) {
 		return CollectionUtils.isEmpty(buildpacks) ? EMPTY : new Buildpacks(buildpacks);
 	}
 

buildpack/spring-boot-buildpack-platform/src/main/java/org/springframework/boot/buildpack/platform/build/EphemeralBuilder.java

@@ -65,7 +65,7 @@ class EphemeralBuilder {
 	 * @param buildpacks an optional set of buildpacks to apply
 	 */
 	EphemeralBuilder(BuildOwner buildOwner, Image builderImage, ImageReference targetImage,
-			BuilderMetadata builderMetadata, Creator creator, Map<String, String> env,
+			BuilderMetadata builderMetadata, Creator creator, @Nullable Map<String, String> env,
 			@Nullable Buildpacks buildpacks) {
 		this.name = ImageReference.random("pack.local/builder/").inTaggedForm();
 		this.buildOwner = buildOwner;
@@ -129,7 +129,7 @@ class EphemeralBuilder {
 	 * @return the ephemeral builder archive
 	 * @throws IOException on IO error
 	 */
-	ImageArchive getArchive(String applicationDirectory) throws IOException {
+	ImageArchive getArchive(@Nullable String applicationDirectory) throws IOException {
 		return ImageArchive.from(this.builderImage, (update) -> {
 			this.archiveUpdate.accept(update);
 			if (StringUtils.hasLength(applicationDirectory)) {

buildpack/spring-boot-buildpack-platform/src/main/java/org/springframework/boot/buildpack/platform/docker/DockerApi.java

@@ -207,7 +207,7 @@ public class DockerApi {
 		 * @return the {@link ImageApi pulled image} instance
 		 * @throws IOException on IO error
 		 */
-		public Image pull(ImageReference reference, ImagePlatform platform,
+		public Image pull(ImageReference reference, @Nullable ImagePlatform platform,
 				UpdateListener<PullImageUpdateEvent> listener) throws IOException {
 			return pull(reference, platform, listener, null);
 		}

buildpack/spring-boot-buildpack-platform/src/main/java/org/springframework/boot/buildpack/platform/docker/TotalProgressBar.java

@@ -19,6 +19,8 @@ package org.springframework.boot.buildpack.platform.docker;
 import java.io.PrintStream;
 import java.util.function.Consumer;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.util.StringUtils;
 
 /**
@@ -62,7 +64,7 @@ public class TotalProgressBar implements Consumer<TotalProgressEvent> {
 	 * @param bookend if bookends should be printed
 	 * @param out the output print stream to use
 	 */
-	public TotalProgressBar(String prefix, char progressChar, boolean bookend, PrintStream out) {
+	public TotalProgressBar(@Nullable String prefix, char progressChar, boolean bookend, PrintStream out) {
 		this.progressChar = progressChar;
 		this.bookend = bookend;
 		if (StringUtils.hasLength(prefix)) {

buildpack/spring-boot-buildpack-platform/src/main/java/org/springframework/boot/buildpack/platform/docker/configuration/DockerRegistryConfigAuthentication.java

@@ -49,7 +49,7 @@ class DockerRegistryConfigAuthentication implements DockerRegistryAuthentication
 
 	private final BiConsumer<String, Exception> credentialHelperExceptionHandler;
 
-	private final Function<String, CredentialHelper> credentialHelperFactory;
+	private final Function<String, @Nullable CredentialHelper> credentialHelperFactory;
 
 	private final DockerConfig dockerConfig;
 
@@ -61,7 +61,7 @@ class DockerRegistryConfigAuthentication implements DockerRegistryAuthentication
 
 	DockerRegistryConfigAuthentication(@Nullable DockerRegistryAuthentication fallback,
 			BiConsumer<String, Exception> credentialHelperExceptionHandler, Environment environment,
-			Function<String, CredentialHelper> credentialHelperFactory) {
+			Function<String, @Nullable CredentialHelper> credentialHelperFactory) {
 		this.fallback = fallback;
 		this.credentialHelperExceptionHandler = credentialHelperExceptionHandler;
 		this.dockerConfig = DockerConfigurationMetadata.from(environment).getConfiguration();

buildpack/spring-boot-buildpack-platform/src/main/java/org/springframework/boot/buildpack/platform/docker/ssl/KeyStoreFactory.java

@@ -50,7 +50,7 @@ final class KeyStoreFactory {
 	 * @param alias the alias to use for KeyStore entries
 	 * @return the {@code KeyStore}
 	 */
-	static KeyStore create(Path certPath, Path keyPath, String alias) {
+	static KeyStore create(Path certPath, @Nullable Path keyPath, String alias) {
 		try {
 			KeyStore keyStore = getKeyStore();
 			String certificateText = Files.readString(certPath);

buildpack/spring-boot-buildpack-platform/src/main/java/org/springframework/boot/buildpack/platform/docker/transport/DockerEngineException.java

@@ -34,14 +34,14 @@ public class DockerEngineException extends RuntimeException {
 
 	private final int statusCode;
 
-	private final String reasonPhrase;
+	private final @Nullable String reasonPhrase;
 
 	private final @Nullable Errors errors;
 
 	private final @Nullable Message responseMessage;
 
-	public DockerEngineException(String host, URI uri, int statusCode, String reasonPhrase, @Nullable Errors errors,
-			@Nullable Message responseMessage) {
+	public DockerEngineException(String host, URI uri, int statusCode, @Nullable String reasonPhrase,
+			@Nullable Errors errors, @Nullable Message responseMessage) {
 		super(buildMessage(host, uri, statusCode, reasonPhrase, errors, responseMessage));
 		this.statusCode = statusCode;
 		this.reasonPhrase = reasonPhrase;
@@ -61,7 +61,7 @@ public class DockerEngineException extends RuntimeException {
 	 * Return the reason phrase returned by the Docker API.
 	 * @return the reasonPhrase
 	 */
-	public String getReasonPhrase() {
+	public @Nullable String getReasonPhrase() {
 		return this.reasonPhrase;
 	}
 
@@ -83,7 +83,7 @@ public class DockerEngineException extends RuntimeException {
 		return this.responseMessage;
 	}
 
-	private static String buildMessage(String host, URI uri, int statusCode, String reasonPhrase,
+	private static String buildMessage(String host, URI uri, int statusCode, @Nullable String reasonPhrase,
 			@Nullable Errors errors, @Nullable Message responseMessage) {
 		Assert.notNull(host, "'host' must not be null");
 		Assert.notNull(uri, "'uri' must not be null");