Don't write the default loader classes when a custom launcher is used

spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/bundling/BootArchiveSupport.java

@@ -17,6 +17,7 @@
 package org.springframework.boot.gradle.bundling;
 
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashSet;
 import java.util.Map;
 import java.util.Set;
@@ -41,19 +42,30 @@ import org.gradle.api.tasks.util.PatternSet;
  */
 class BootArchiveSupport {
 
+	private static final Set<String> DEFAULT_LAUNCHER_CLASSES;
+
+	static {
+		Set<String> defaultLauncherClasses = new HashSet<String>();
+		defaultLauncherClasses.add("org.springframework.boot.loader.JarLauncher");
+		defaultLauncherClasses.add("org.springframework.boot.loader.PropertiesLauncher");
+		defaultLauncherClasses.add("org.springframework.boot.loader.WarLauncher");
+		DEFAULT_LAUNCHER_CLASSES = Collections.unmodifiableSet(defaultLauncherClasses);
+	}
+
 	private final PatternSet requiresUnpack = new PatternSet();
 
 	private final Set<String> storedPathPrefixes;
 
 	private final PatternSet exclusions = new PatternSet();
 
-	private String loaderMainClass;
+	private final String loaderMainClass;
 
 	private LaunchScriptConfiguration launchScript = new LaunchScriptConfiguration();
 
 	private boolean excludeDevtools = true;
 
-	BootArchiveSupport(String... storedPathPrefixes) {
+	BootArchiveSupport(String loaderMainClass, String... storedPathPrefixes) {
+		this.loaderMainClass = loaderMainClass;
 		this.storedPathPrefixes = new HashSet<>(Arrays.asList(storedPathPrefixes));
 		this.requiresUnpack.include(Specs.satisfyNone());
 		configureExclusions();
@@ -67,21 +79,18 @@ class BootArchiveSupport {
 
 	CopyAction createCopyAction(Jar jar) {
 		CopyAction copyAction = new BootZipCopyAction(jar.getArchivePath(),
-				jar.isPreserveFileTimestamps(), this.requiresUnpack.getAsSpec(),
-				this.exclusions.getAsExcludeSpec(), this.launchScript,
-				this.storedPathPrefixes);
+				jar.isPreserveFileTimestamps(), isUsingDefaultLoader(jar),
+				this.requiresUnpack.getAsSpec(), this.exclusions.getAsExcludeSpec(),
+				this.launchScript, this.storedPathPrefixes);
 		if (!jar.isReproducibleFileOrder()) {
 			return copyAction;
 		}
 		return new ReproducibleOrderingCopyAction(copyAction);
 	}
 
-	String getLoaderMainClass() {
-		return this.loaderMainClass;
-	}
-
-	void setLoaderMainClass(String loaderMainClass) {
-		this.loaderMainClass = loaderMainClass;
+	private boolean isUsingDefaultLoader(Jar jar) {
+		return DEFAULT_LAUNCHER_CLASSES
+				.contains(jar.getManifest().getAttributes().get("Main-Class"));
 	}
 
 	LaunchScriptConfiguration getLaunchScript() {

spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/bundling/BootJar.java

@@ -35,14 +35,14 @@ import org.gradle.api.tasks.bundling.Jar;
  */
 public class BootJar extends Jar implements BootArchive {
 
-	private BootArchiveSupport support = new BootArchiveSupport("BOOT-INF/lib");
+	private BootArchiveSupport support = new BootArchiveSupport(
+			"org.springframework.boot.loader.JarLauncher", "BOOT-INF/lib");
 
 	private FileCollection classpath;
 
 	private String mainClass;
 
 	public BootJar() {
-		this.support.setLoaderMainClass("org.springframework.boot.loader.JarLauncher");
 		CopySpec bootInf = getRootSpec().addChildBeforeSpec(getMainSpec())
 				.into("BOOT-INF");
 		bootInf.into("lib", classpathFiles(File::isFile));

spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/bundling/BootWar.java

@@ -36,7 +36,8 @@ import org.gradle.api.tasks.bundling.War;
  */
 public class BootWar extends War implements BootArchive {
 
-	private final BootArchiveSupport support = new BootArchiveSupport("WEB-INF/lib/",
+	private final BootArchiveSupport support = new BootArchiveSupport(
+			"org.springframework.boot.loader.WarLauncher", "WEB-INF/lib/",
 			"WEB-INF/lib-provided");
 
 	private String mainClass;
@@ -44,7 +45,6 @@ public class BootWar extends War implements BootArchive {
 	private FileCollection providedClasspath;
 
 	public BootWar() {
-		this.support.setLoaderMainClass("org.springframework.boot.loader.WarLauncher");
 		getWebInf().into("lib-provided", (copySpec) -> {
 			copySpec.from((Callable<Iterable<File>>) () -> {
 				return this.providedClasspath == null ? Collections.emptyList()

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

@@ -53,6 +53,8 @@ class BootZipCopyAction implements CopyAction {
 
 	private final boolean preserveFileTimestamps;
 
+	private final boolean includeDefaultLoader;
+
 	private final Spec<FileTreeElement> requiresUnpack;
 
 	private final Spec<FileTreeElement> exclusions;
@@ -62,10 +64,12 @@ class BootZipCopyAction implements CopyAction {
 	private final Set<String> storedPathPrefixes;
 
 	BootZipCopyAction(File output, boolean preserveFileTimestamps,
-			Spec<FileTreeElement> requiresUnpack, Spec<FileTreeElement> exclusions,
-			LaunchScriptConfiguration launchScript, Set<String> storedPathPrefixes) {
+			boolean includeDefaultLoader, Spec<FileTreeElement> requiresUnpack,
+			Spec<FileTreeElement> exclusions, LaunchScriptConfiguration launchScript,
+			Set<String> storedPathPrefixes) {
 		this.output = output;
 		this.preserveFileTimestamps = preserveFileTimestamps;
+		this.includeDefaultLoader = includeDefaultLoader;
 		this.requiresUnpack = requiresUnpack;
 		this.exclusions = exclusions;
 		this.launchScript = launchScript;
@@ -79,7 +83,7 @@ class BootZipCopyAction implements CopyAction {
 			FileOutputStream fileStream = new FileOutputStream(this.output);
 			writeLaunchScriptIfNecessary(fileStream);
 			zipStream = new ZipOutputStream(fileStream);
-			writeLoaderClasses(zipStream);
+			writeLoaderClassesIfNecessary(zipStream);
 		}
 		catch (IOException ex) {
 			throw new GradleException("Failed to create " + this.output, ex);
@@ -102,8 +106,13 @@ class BootZipCopyAction implements CopyAction {
 		};
 	}
 
-	private void writeLoaderClasses(ZipOutputStream out) {
+	private void writeLoaderClassesIfNecessary(ZipOutputStream out) {
+		if (this.includeDefaultLoader) {
+			writeLoaderClasses(out);
+		}
+	}
 
+	private void writeLoaderClasses(ZipOutputStream out) {
 		ZipEntry entry;
 		try (ZipInputStream in = new ZipInputStream(getClass()
 				.getResourceAsStream("/META-INF/loader/spring-boot-loader.jar"))) {

spring-boot-tools/spring-boot-gradle-plugin/src/test/java/org/springframework/boot/gradle/bundling/AbstractBootArchiveTests.java

@@ -135,6 +135,20 @@ public abstract class AbstractBootArchiveTests<T extends Jar & BootArchive> {
 		}
 	}
 
+	@Test
+	public void loaderIsWrittenToTheRootOfTheJarWhenUsingThePropertiesLauncher()
+			throws IOException {
+		this.task.setMainClass("com.example.Main");
+		this.task.execute();
+		this.task.getManifest().getAttributes().put("Main-Class",
+				"org.springframework.boot.loader.PropertiesLauncher");
+		try (JarFile jarFile = new JarFile(this.task.getArchivePath())) {
+			assertThat(jarFile.getEntry(
+					"org/springframework/boot/loader/LaunchedURLClassLoader.class"))
+							.isNotNull();
+		}
+	}
+
 	@Test
 	public void unpackCommentIsAddedToEntryIdentifiedByAPattern() throws IOException {
 		this.task.setMainClass("com.example.Main");
@@ -207,6 +221,9 @@ public abstract class AbstractBootArchiveTests<T extends Jar & BootArchive> {
 					.isEqualTo("com.example.CustomLauncher");
 			assertThat(jarFile.getManifest().getMainAttributes().getValue("Start-Class"))
 					.isEqualTo("com.example.Main");
+			assertThat(jarFile.getEntry(
+					"org/springframework/boot/loader/LaunchedURLClassLoader.class"))
+							.isNull();
 		}
 	}