Support for custom repackaging to change loader classes

spring-boot-docs/src/main/asciidoc/build-tool-plugins.adoc

@@ -480,9 +480,12 @@ The following configuration options are available:
 |The name of the custom configuration.
 
 |`layout`
-|The type of archive, corresponding to how the dependencies are laid out inside
- (defaults to a guess based on the archive type). See
- <<build-tool-plugins-gradle-configuration-layouts,available layouts for more details>>.
+|The `LayoutType` of archive, corresponding to how the dependencies are laid out inside
+ (defaults to a guess based on the archive type). See 
+<<build-tool-plugins-gradle-configuration-layouts,available layouts for more details>>.
+
+|`layoutFactory`
+|A factory for the actual `Layout` derived from the `LayoutType`. If the factory is provided then the layout is ignored.
 
 |`requiresUnpack`
 |A list of dependencies (in the form "`groupId:artifactId`" that must be unpacked from
@@ -493,7 +496,7 @@ The following configuration options are available:
 
 
 [[build-tool-plugins-gradle-configuration-layouts]]
-==== Available layouts
+==== Available built-in layouts
 
 The `layout` attribute configures the format of the archive and whether the bootstrap
 loader should be included or not. The following layouts are available:
@@ -530,6 +533,40 @@ loader should be included or not. The following layouts are available:
 
 
 
+[[build-tool-plugins-gradle-configuration-custom-layout]]
+==== Using a custom layout
+If you have custom requirements for how to arrange the dependencies and loader classes
+inside the repackaged jar, you can use a custom layout in addition to the built-in values.
+Any library which defines one or more `LayoutFactory` implementations can be added to the 
+build script dependencies and then the layout type becomes available in the `springBoot` 
+configuration. For example
+
+[source,groovy,indent=0,subs="verbatim,attributes"]
+----
+buildscript {
+	ext {
+		springBootVersion = '1.5.0.BUILD-SNAPSHOT'
+		customVersion = '0.0.1.BUILD-SNAPSHOT'
+	}
+	repositories {
+		mavenLocal()
+		mavenCentral()
+	}
+	dependencies {
+		classpath("com.example:custom-layout:${customVersion}")
+		classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
+	}
+}
+
+springBoot {
+	layoutFactory = new com.example.CustomLayoutFactory()
+}
+----
+
+If there is only one custom `LayoutFactory` on the build classpath and
+it is listed in `META-INF/spring.factories` then it is unnecessary to
+explicitly set it in the `springBoot` configuration.
+
 [[build-tool-plugins-understanding-the-gradle-plugin]]
 === Understanding how the Gradle plugin works
 When `spring-boot` is applied to your Gradle project a default task named `bootRepackage`

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

@@ -21,11 +21,14 @@
 import java.util.Set;
 
 import groovy.lang.Closure;
+
 import org.gradle.api.Project;
 import org.gradle.api.plugins.JavaPlugin;
 
 import org.springframework.boot.gradle.buildinfo.BuildInfo;
 import org.springframework.boot.loader.tools.Layout;
+import org.springframework.boot.loader.tools.LayoutFactory;
+import org.springframework.boot.loader.tools.LayoutType;
 import org.springframework.boot.loader.tools.Layouts;
 
 /**
@@ -90,6 +93,11 @@ public class SpringBootPluginExtension {
 	 */
 	LayoutType layout;
 
+	/**
+	 * The layout factory to use to convert a layout type into an actual layout.
+	 */
+	LayoutFactory layoutFactory = Layouts.getDefaultLayoutFactory();
+
 	/**
 	 * Libraries that must be unpacked from fat jars in order to run. Use Strings in the
 	 * form {@literal groupId:artifactId}.
@@ -142,10 +150,21 @@ public SpringBootPluginExtension(Project project) {
 
 	/**
 	 * Convenience method for use in a custom task.
+	 * @param file the file to use to guess the layout if necessary
 	 * @return the Layout to use or null if not explicitly set
 	 */
-	public Layout convertLayout() {
-		return (this.layout == null ? null : this.layout.layout);
+	public Layout convertLayout(File file) {
+		Layout result;
+		if (this.layoutFactory != null) {
+			result = this.layoutFactory.getLayout();
+		}
+		else if (this.layout == null) {
+			result = Layouts.forFile(file);
+		}
+		else {
+			result = Layouts.forType(this.layout);
+		}
+		return result;
 	}
 
 	public String getMainClass() {
@@ -196,6 +215,14 @@ public void setLayout(LayoutType layout) {
 		this.layout = layout;
 	}
 
+	public LayoutFactory getLayoutFactory() {
+		return this.layoutFactory;
+	}
+
+	public void setLayoutFactory(LayoutFactory layoutFactory) {
+		this.layoutFactory = layoutFactory;
+	}
+
 	public Set<String> getRequiresUnpack() {
 		return this.requiresUnpack;
 	}
@@ -276,29 +303,4 @@ public void buildInfo(Closure<?> taskConfigurer) {
 		}
 	}
 
-	/**
-	 * Layout Types.
-	 */
-	enum LayoutType {
-
-		JAR(new Layouts.Jar()),
-
-		WAR(new Layouts.War()),
-
-		ZIP(new Layouts.Expanded()),
-
-		DIR(new Layouts.Expanded()),
-
-		MODULE(new Layouts.Module()),
-
-		NONE(new Layouts.None());
-
-		Layout layout;
-
-		LayoutType(Layout layout) {
-			this.layout = layout;
-		}
-
-	}
-
 }

spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/repackage/RepackageTask.java

@@ -217,9 +217,7 @@ private void repackage(File file) {
 			}
 			Repackager repackager = new LoggingRepackager(file);
 			setMainClass(repackager);
-			if (this.extension.convertLayout() != null) {
-				repackager.setLayout(this.extension.convertLayout());
-			}
+			repackager.setLayout(this.extension.convertLayout(file));
 			repackager.setBackupSource(this.extension.isBackupSource());
 			try {
 				LaunchScript launchScript = getLaunchScript();

spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/JarWriter.java

@@ -53,8 +53,6 @@
  */
 public class JarWriter {
 
-	private static final String NESTED_LOADER_JAR = "META-INF/loader/spring-boot-loader.jar";
-
 	private static final int BUFFER_SIZE = 32 * 1024;
 
 	private final JarOutputStream jarOutput;
@@ -206,9 +204,20 @@ private long getNestedLibraryTime(File file) {
 	/**
 	 * Write the required spring-boot-loader classes to the JAR.
 	 * @throws IOException if the classes cannot be written
+	 * @deprecated us {@link #writeLoaderClasses(String)} instead
 	 */
+	@Deprecated
 	public void writeLoaderClasses() throws IOException {
-		URL loaderJar = getClass().getClassLoader().getResource(NESTED_LOADER_JAR);
+		writeLoaderClasses(Layouts.DEFAULT_LOADER_JAR);
+	}
+
+	/**
+	 * Write the required spring-boot-loader classes to the JAR.
+	 * @param loaderJarPath the path to the loader jar (in the classpath)
+	 * @throws IOException if the classes cannot be written
+	 */
+	public void writeLoaderClasses(String loaderJarPath) throws IOException {
+		URL loaderJar = getClass().getClassLoader().getResource(loaderJarPath);
 		JarInputStream inputStream = new JarInputStream(
 				new BufferedInputStream(loaderJar.openStream()));
 		JarEntry entry;

spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/Layout.java

@@ -40,15 +40,25 @@ public interface Layout {
 	String getLibraryDestination(String libraryName, LibraryScope scope);
 
 	/**
-	 * Returns the location of classes within the archive.
+	 * Returns the location of classes within the archive. Empty if the location is the
+	 * root path, otherwise ends with a slash ('/').
 	 * @return the classes location
 	 */
 	String getClassesLocation();
 
 	/**
-	 * Returns if loader classes should be included to make the archive executable.
+	 * Returns if loader classes should be included to make the archive executable. If
+	 * true, then {@link #getLoaderJarPath()} should point to a valid jar file that
+	 * contains the loader classes.
 	 * @return if the layout is executable
 	 */
 	boolean isExecutable();
 
+	/**
+	 * Returns the path to a nested jar that contains the loader, and which will be
+	 * unpacked into the root of the repackaged jar.
+	 * @return the path to a nested jar that contains the loader
+	 */
+	String getLoaderJarPath();
+
 }

spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/LayoutFactory.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2012-2015 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.loader.tools;
+
+/**
+ * Strategy for creating instances of {@link Layout}.
+ *
+ * @author Dave Syer
+ *
+ */
+public interface LayoutFactory {
+
+	Layout getLayout();
+
+}

spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/LayoutType.java

@@ -0,0 +1,80 @@
+/*
+ * Copyright 2012-2015 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.loader.tools;
+
+import java.io.File;
+
+/**
+ * Archive layout types.
+ *
+ * @author Dave Syer
+ */
+public enum LayoutType {
+
+	/**
+	 * Jar Layout.
+	 */
+	JAR,
+
+	/**
+	 * War Layout.
+	 */
+	WAR,
+
+	/**
+	 * Zip Layout.
+	 */
+	ZIP,
+
+	/**
+	 * Dir Layout.
+	 */
+	DIR,
+
+	/**
+	 * Module Layout.
+	 */
+	MODULE,
+
+	/**
+	 * No Layout.
+	 */
+	NONE;
+
+
+	/**
+	 * Return a layout type for the given source file.
+	 * @param file the source file
+	 * @return a {@link Layout}
+	 */
+	public static LayoutType forFile(File file) {
+		if (file == null) {
+			throw new IllegalArgumentException("File must not be null");
+		}
+		if (file.getName().toLowerCase().endsWith(".jar")) {
+			return JAR;
+		}
+		if (file.getName().toLowerCase().endsWith(".war")) {
+			return WAR;
+		}
+		if (file.isDirectory() || file.getName().toLowerCase().endsWith(".zip")) {
+			return ZIP;
+		}
+		throw new IllegalArgumentException("Unable to deduce layout for '" + file + "'");
+	}
+
+}