Support for custom layout types to change loader classes

A layout can
also optionally change the loader jar that is unpacked in the root
of the repackaged archive by implementing a new method in Layout.

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

@@ -53,8 +53,6 @@ import org.springframework.lang.UsesJava7;
  */
 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 @@ public class JarWriter {
 	/**
 	 * 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

@@ -18,14 +18,14 @@ package org.springframework.boot.loader.tools;
 
 /**
  * Strategy for creating instances of {@link Layout}.
- * 
+ *
  * @author Dave Syer
  *
  */
 public interface LayoutFactory {
-	
+
 	Layout getLayout();
-	
+
 	String getName();
 
 }

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

@@ -24,6 +24,8 @@ import org.springframework.core.io.support.SpringFactoriesLoader;
 
 /**
  * Archive layout types.
+ *
+ * @author Dave Syer
  */
 public enum LayoutType {
 

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

@@ -33,6 +33,11 @@ import java.util.Set;
  */
 public final class Layouts {
 
+	/**
+	 * Default value for {@link #getLoaderJarPath()}.
+	 */
+	public static final String DEFAULT_LOADER_JAR = "META-INF/loader/spring-boot-loader.jar";
+
 	private Layouts() {
 	}
 
@@ -87,6 +92,11 @@ public final class Layouts {
 			return true;
 		}
 
+		@Override
+		public String getLoaderJarPath() {
+			return DEFAULT_LOADER_JAR;
+		}
+
 	}
 
 	/**
@@ -116,6 +126,11 @@ public final class Layouts {
 			return false;
 		}
 
+		@Override
+		public String getLoaderJarPath() {
+			return DEFAULT_LOADER_JAR;
+		}
+
 	}
 
 	/**
@@ -154,6 +169,11 @@ public final class Layouts {
 			return true;
 		}
 
+		@Override
+		public String getLoaderJarPath() {
+			return DEFAULT_LOADER_JAR;
+		}
+
 	}
 
 	/**
@@ -188,6 +208,11 @@ public final class Layouts {
 			return false;
 		}
 
+		@Override
+		public String getLoaderJarPath() {
+			return DEFAULT_LOADER_JAR;
+		}
+
 	}
 
 }

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

@@ -217,7 +217,7 @@ public class Repackager {
 			}
 			writeNestedLibraries(standardLibraries, seen, writer);
 			if (this.layout.isExecutable()) {
-				writer.writeLoaderClasses();
+				writer.writeLoaderClasses(this.layout.getLoaderJarPath());
 			}
 		}
 		finally {

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

@@ -28,14 +28,15 @@ public class LayoutTypeTests {
 
 	@Test
 	public void standardType() {
-		assertThat(LayoutType.layout("DIR")).isEqualTo(LayoutType.valueOf("DIR").layout());
+		assertThat(LayoutType.layout("DIR"))
+				.isEqualTo(LayoutType.valueOf("DIR").layout());
 	}
 
 	@Test
 	public void customType() {
 		assertThat(LayoutType.layout("CUSTOM")).isNotNull();
 	}
-	
+
 	public static class TestLayoutFactory implements LayoutFactory {
 
 		@Override
@@ -46,6 +47,7 @@ public class LayoutTypeTests {
 		@Override
 		public String getName() {
 			return "CUSTOM";
-		}}
+		}
+	}
 
 }