Add 'module' repacker layout

Add a 'module' layout for the repackager which includes all 'compile'
and 'runtime' scope dependencies and does not require a main class.

Fixes gh-1941

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

@@ -48,6 +48,8 @@ public class SpringBootPluginExtension {
 
 		DIR(new Layouts.Expanded()),
 
+		MODULE(new Layouts.Module()),
+
 		NONE(new Layouts.None());
 
 		Layout layout;

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

@@ -44,4 +44,9 @@ public interface Layout {
 	 */
 	String getClassesLocation();
 
+	/**
+	 * Returns if loader classes should be included to make the archive executable.
+	 */
+	boolean isExecutable();
+
 }

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

@@ -69,6 +69,12 @@ public class Layouts {
 		public String getClassesLocation() {
 			return "";
 		}
+
+		@Override
+		public boolean isExecutable() {
+			return true;
+		}
+
 	}
 
 	/**
@@ -84,7 +90,7 @@ public class Layouts {
 	}
 
 	/**
-	 * Executable expanded archive layout.
+	 * No layout.
 	 */
 	public static class None extends Jar {
 
@@ -92,6 +98,12 @@ public class Layouts {
 		public String getLauncherClassName() {
 			return null;
 		}
+
+		@Override
+		public boolean isExecutable() {
+			return false;
+		}
+
 	}
 
 	/**
@@ -122,6 +134,42 @@ public class Layouts {
 		public String getClassesLocation() {
 			return "WEB-INF/classes/";
 		}
+
+		@Override
+		public boolean isExecutable() {
+			return true;
+		}
+
+	}
+
+	/**
+	 * Module layout (designed to be used as a "plug-in")
+	 */
+	public static class Module implements Layout {
+
+		@Override
+		public String getLauncherClassName() {
+			return null;
+		}
+
+		@Override
+		public String getLibraryDestination(String libraryName, LibraryScope scope) {
+			if (LibraryScope.COMPILE.equals(scope) || LibraryScope.RUNTIME.equals(scope)) {
+				return "lib/";
+			}
+			return null;
+		}
+
+		@Override
+		public String getClassesLocation() {
+			return "";
+		}
+
+		@Override
+		public boolean isExecutable() {
+			return false;
+		}
+
 	}
 
 }

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

@@ -177,7 +177,7 @@ public class Repackager {
 				}
 			});
 
-			if (!(this.layout instanceof Layouts.None)) {
+			if (this.layout.isExecutable()) {
 				writer.writeLoaderClasses();
 			}
 		}

spring-boot-tools/spring-boot-loader-tools/src/test/java/org/springframework/boot/loader/tools/LayoutsTests.java

@@ -24,6 +24,7 @@ import org.junit.rules.ExpectedException;
 
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.instanceOf;
+import static org.hamcrest.Matchers.nullValue;
 import static org.junit.Assert.assertThat;
 
 /**
@@ -81,4 +82,15 @@ public class LayoutsTests {
 				equalTo("WEB-INF/lib/"));
 	}
 
+	@Test
+	public void moduleLayout() throws Exception {
+		Layout layout = new Layouts.Module();
+		assertThat(layout.getLibraryDestination("lib.jar", LibraryScope.COMPILE),
+				equalTo("lib/"));
+		assertThat(layout.getLibraryDestination("lib.jar", LibraryScope.PROVIDED),
+				nullValue());
+		assertThat(layout.getLibraryDestination("lib.jar", LibraryScope.RUNTIME),
+				equalTo("lib/"));
+	}
+
 }

spring-boot-tools/spring-boot-maven-plugin/src/it/module/pom.xml

@@ -0,0 +1,48 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+	<groupId>org.springframework.boot.maven.it</groupId>
+	<artifactId>module</artifactId>
+	<version>0.0.1.BUILD-SNAPSHOT</version>
+	<properties>
+		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+	</properties>
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>@project.groupId@</groupId>
+				<artifactId>@project.artifactId@</artifactId>
+				<version>@project.version@</version>
+				<executions>
+					<execution>
+						<goals>
+							<goal>repackage</goal>
+						</goals>
+						<configuration>
+							<layout>MODULE</layout>
+						</configuration>
+					</execution>
+				</executions>
+			</plugin>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-jar-plugin</artifactId>
+				<version>2.4</version>
+			</plugin>
+		</plugins>
+	</build>
+	<dependencies>
+		<dependency>
+			<groupId>org.springframework</groupId>
+			<artifactId>spring-context</artifactId>
+			<version>@spring.version@</version>
+		</dependency>
+		<dependency>
+			<groupId>javax.servlet</groupId>
+			<artifactId>javax.servlet-api</artifactId>
+			<version>@servlet-api.version@</version>
+			<scope>provided</scope>
+		</dependency>
+	</dependencies>
+</project>

spring-boot-tools/spring-boot-maven-plugin/src/it/module/src/main/java/org/test/SampleModule.java

@@ -0,0 +1,5 @@
+package org.test;
+
+public class SampleModule {
+
+}

spring-boot-tools/spring-boot-maven-plugin/src/it/module/verify.groovy

@@ -0,0 +1,5 @@
+import java.io.*;
+import org.springframework.boot.maven.*;
+
+Verify.verifyModule(new File( basedir, "target/module-0.0.1.BUILD-SNAPSHOT.jar" ));
+

spring-boot-tools/spring-boot-maven-plugin/src/main/java/org/springframework/boot/maven/RepackageMojo.java

@@ -191,8 +191,37 @@ public class RepackageMojo extends AbstractDependencyFilterMojo {
 	}
 
 	public static enum LayoutType {
-		JAR(new Layouts.Jar()), WAR(new Layouts.War()), ZIP(new Layouts.Expanded()), DIR(
-				new Layouts.Expanded()), NONE(new Layouts.None());
+
+		/**
+		 * Jar Layout
+		 */
+		JAR(new Layouts.Jar()),
+
+		/**
+		 * War Layout
+		 */
+		WAR(new Layouts.War()),
+
+		/**
+		 * Zip Layout
+		 */
+		ZIP(new Layouts.Expanded()),
+
+		/**
+		 * Dir Layout
+		 */
+		DIR(new Layouts.Expanded()),
+
+		/**
+		 * Module Layout
+		 */
+		MODULE(new Layouts.Module()),
+
+		/**
+		 * No Layout
+		 */
+		NONE(new Layouts.None());
+
 		private final Layout layout;
 
 		public Layout layout() {

spring-boot-tools/spring-boot-maven-plugin/src/test/java/org/springframework/boot/maven/Verify.java

@@ -27,6 +27,7 @@ import java.util.zip.ZipEntry;
 import java.util.zip.ZipFile;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
 /**
@@ -54,6 +55,10 @@ public class Verify {
 		new ZipArchiveVerification(file).verify();
 	}
 
+	public static void verifyModule(File file) throws Exception {
+		new ModuleArchiveVerification(file).verify();
+	}
+
 	public static class ArchiveVerifier {
 
 		private final ZipFile zipFile;
@@ -235,4 +240,28 @@ public class Verify {
 		}
 	}
 
+	private static class ModuleArchiveVerification extends AbstractArchiveVerification {
+
+		public ModuleArchiveVerification(File file) {
+			super(file);
+		}
+
+		@Override
+		protected void verifyZipEntries(ArchiveVerifier verifier) throws Exception {
+			super.verifyZipEntries(verifier);
+			verifier.assertHasEntryNameStartingWith("lib/spring-context");
+			verifier.assertHasEntryNameStartingWith("lib/spring-core");
+			verifier.assertHasNoEntryNameStartingWith("lib/javax.servlet-api-3");
+			assertFalse("Unpacked launcher classes", verifier.hasEntry("org/"
+					+ "springframework/boot/loader/JarLauncher.class"));
+			assertTrue("Own classes", verifier.hasEntry("org/"
+					+ "test/SampleModule.class"));
+		}
+
+		@Override
+		protected void verifyManifest(Manifest manifest) throws Exception {
+		}
+
+	}
+
 }