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

See gh-47263

build-plugin/spring-boot-maven-plugin/src/main/java/org/springframework/boot/maven/ArtifactsLibraries.java

@@ -79,7 +79,7 @@ public class ArtifactsLibraries implements Libraries {
 	 * @since 2.4.0
 	 */
 	public ArtifactsLibraries(Set<Artifact> artifacts, Collection<MavenProject> localProjects,
-			Collection<Dependency> unpacks, Log log) {
+			@Nullable Collection<Dependency> unpacks, Log log) {
 		this(artifacts, artifacts, localProjects, unpacks, log);
 	}
 

build-plugin/spring-boot-maven-plugin/src/main/java/org/springframework/boot/maven/ClassPath.java

@@ -33,6 +33,8 @@ import java.util.function.UnaryOperator;
 import java.util.stream.Collector;
 import java.util.stream.Collectors;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.util.StringUtils;
 
 /**
@@ -125,12 +127,12 @@ final class ClassPath {
 	 * @param urls the class path URLs
 	 * @return a new {@link ClassPath} instance
 	 */
-	static ClassPath of(UnaryOperator<String> getSystemProperty, List<URL> urls) {
+	static ClassPath of(UnaryOperator<@Nullable String> getSystemProperty, List<URL> urls) {
 		boolean preferArgFile = urls.size() > 1 && isWindows(getSystemProperty);
 		return new ClassPath(preferArgFile, urls.stream().map(ClassPath::toPathString).collect(JOIN_BY_PATH_SEPARATOR));
 	}
 
-	private static boolean isWindows(UnaryOperator<String> getSystemProperty) {
+	private static boolean isWindows(UnaryOperator<@Nullable String> getSystemProperty) {
 		String os = getSystemProperty.apply("os.name");
 		return StringUtils.hasText(os) && os.toLowerCase(Locale.ROOT).contains("win");
 	}

build-plugin/spring-boot-maven-plugin/src/main/java/org/springframework/boot/maven/CommandLineBuilder.java

@@ -51,7 +51,8 @@ final class CommandLineBuilder {
 		return new CommandLineBuilder(mainClass);
 	}
 
-	CommandLineBuilder withJvmArguments(String... jvmArguments) {
+	// Do not use String @Nullable ... jvmArguments, Maven can't deal with that
+	CommandLineBuilder withJvmArguments(@Nullable String... jvmArguments) {
 		if (jvmArguments != null) {
 			this.options.addAll(Arrays.stream(jvmArguments).filter(Objects::nonNull).toList());
 		}
@@ -75,7 +76,8 @@ final class CommandLineBuilder {
 		return this;
 	}
 
-	CommandLineBuilder withArguments(String... arguments) {
+	// Do not use String @Nullable ... arguments, Maven can't deal with that
+	CommandLineBuilder withArguments(@Nullable String... arguments) {
 		if (arguments != null) {
 			this.arguments.addAll(Arrays.stream(arguments).filter(Objects::nonNull).toList());
 		}

build-plugin/spring-boot-maven-plugin/src/main/java/org/springframework/boot/maven/Docker.java

@@ -230,7 +230,8 @@ public class Docker {
 		public DockerRegistry() {
 		}
 
-		public DockerRegistry(String username, String password, String url, String email) {
+		public DockerRegistry(@Nullable String username, @Nullable String password, @Nullable String url,
+				@Nullable String email) {
 			this.username = username;
 			this.password = password;
 			this.url = url;