Support flat jar layering with Maven

Update the Maven plugin so that layered jars now use the regular "flat"
format. The layers.idx file now describes which layer each file should
be placed.

See gh-20813

Co-authored-by: Phillip Webb <[email protected]>

Author: mbhave

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

@@ -86,7 +86,7 @@ final void writeEntries(JarFile jarFile, EntryTransformer entryTransformer, Unpa
 			JarArchiveEntry entry = new JarArchiveEntry(entries.nextElement());
 			setUpEntry(jarFile, entry);
 			try (ZipHeaderPeekInputStream inputStream = new ZipHeaderPeekInputStream(jarFile.getInputStream(entry))) {
-				EntryWriter entryWriter = new InputStreamEntryWriter(inputStream);
+				EntryWriter entryWriter = new InputStreamEntryWriter(inputStream, false);
 				JarArchiveEntry transformedEntry = entryTransformer.transform(entry);
 				if (transformedEntry != null) {
 					writeEntry(transformedEntry, entryWriter, unpackHandler);
@@ -114,13 +114,18 @@ private void setUpEntry(JarFile jarFile, JarArchiveEntry entry) throws IOExcepti
 	 */
 	@Override
 	public void writeEntry(String entryName, InputStream inputStream) throws IOException {
+		writeEntry(entryName, new InputStreamEntryWriter(inputStream, true));
+	}
+
+	/**
+	 * Writes an entry. The {@code inputStream} is closed once the entry has been written
+	 * @param entryName the name of the entry
+	 * @param entryWriter the entry writer
+	 * @throws IOException if the write fails
+	 */
+	public void writeEntry(String entryName, EntryWriter entryWriter) throws IOException {
 		JarArchiveEntry entry = new JarArchiveEntry(entryName);
-		try {
-			writeEntry(entry, new InputStreamEntryWriter(inputStream));
-		}
-		finally {
-			inputStream.close();
-		}
+		writeEntry(entry, entryWriter);
 	}
 
 	/**
@@ -133,9 +138,7 @@ public void writeNestedLibrary(String location, Library library) throws IOExcept
 		JarArchiveEntry entry = new JarArchiveEntry(location + library.getName());
 		entry.setTime(getNestedLibraryTime(library));
 		new CrcAndSize(library::openStream).setupStoredEntry(entry);
-		try (InputStream inputStream = library.openStream()) {
-			writeEntry(entry, new InputStreamEntryWriter(inputStream), new LibraryUnpackHandler(library));
-		}
+		writeEntry(entry, new InputStreamEntryWriter(library.openStream(), true), new LibraryUnpackHandler(library));
 	}
 
 	/**
@@ -200,7 +203,7 @@ public void writeLoaderClasses(String loaderJarResourceName) throws IOException
 			JarEntry entry;
 			while ((entry = inputStream.getNextJarEntry()) != null) {
 				if (entry.getName().endsWith(".class")) {
-					writeEntry(new JarArchiveEntry(entry), new InputStreamEntryWriter(inputStream));
+					writeEntry(new JarArchiveEntry(entry), new InputStreamEntryWriter(inputStream, false));
 				}
 			}
 		}
@@ -254,7 +257,7 @@ private EntryWriter addUnpackCommentIfNecessary(JarArchiveEntry entry, EntryWrit
 		ByteArrayOutputStream output = new ByteArrayOutputStream();
 		entryWriter.write(output);
 		entry.setComment("UNPACK:" + unpackHandler.sha1Hash(entry.getName()));
-		return new InputStreamEntryWriter(new ByteArrayInputStream(output.toByteArray()));
+		return new InputStreamEntryWriter(new ByteArrayInputStream(output.toByteArray()), true);
 	}
 
 	/**
@@ -264,8 +267,11 @@ private static class InputStreamEntryWriter implements EntryWriter {
 
 		private final InputStream inputStream;
 
-		InputStreamEntryWriter(InputStream inputStream) {
+		private final boolean close;
+
+		InputStreamEntryWriter(InputStream inputStream, boolean close) {
 			this.inputStream = inputStream;
+			this.close = close;
 		}
 
 		@Override
@@ -276,6 +282,9 @@ public void write(OutputStream outputStream) throws IOException {
 				outputStream.write(buffer, 0, bytesRead);
 			}
 			outputStream.flush();
+			if (this.close) {
+				this.inputStream.close();
+			}
 		}
 
 	}

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

@@ -0,0 +1,81 @@
+/*
+ * Copyright 2012-2020 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
+ *
+ *      https://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.BufferedWriter;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.io.OutputStreamWriter;
+import java.nio.charset.StandardCharsets;
+import java.util.List;
+
+import org.springframework.util.LinkedMultiValueMap;
+import org.springframework.util.MultiValueMap;
+
+/**
+ * Index describing the layer to which each entry in a jar belongs.
+ *
+ * @author Madhura Bhave
+ * @author Andy Wilkinson
+ * @since 2.3.0
+ */
+public class LayersIndex {
+
+	private final Iterable<Layer> layers;
+
+	private final MultiValueMap<Layer, String> index = new LinkedMultiValueMap<>();
+
+	/**
+	 * Create a new {@link LayersIndex} backed by the given layers.
+	 * @param layers the layers in the index
+	 */
+	public LayersIndex(Iterable<Layer> layers) {
+		this.layers = layers;
+	}
+
+	/**
+	 * Add an item to the index.
+	 * @param layer the layer of the item
+	 * @param name the name of the item
+	 */
+	public void add(Layer layer, String name) {
+		this.index.add(layer, name);
+	}
+
+	/**
+	 * Write the layer index to an output stream.
+	 * @param out the destination stream
+	 * @throws IOException on IO error
+	 */
+	public void writeTo(OutputStream out) throws IOException {
+		BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(out, StandardCharsets.UTF_8));
+		for (Layer layer : this.layers) {
+			List<String> names = this.index.get(layer);
+			if (names != null) {
+				for (String name : names) {
+					writer.write(layer.toString());
+					writer.write(" ");
+					writer.write(name);
+					writer.write("\n");
+				}
+			}
+		}
+		writer.flush();
+
+	}
+
+}

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

@@ -94,31 +94,14 @@ public String getClasspathIndexFileLocation() {
 			return "BOOT-INF/classpath.idx";
 		}
 
-		@Override
-		public boolean isExecutable() {
-			return true;
-		}
-
-	}
-
-	/**
-	 * Executable JAR layout with support for layers.
-	 */
-	public static class LayeredJar extends Jar implements LayeredLayout {
-
 		@Override
 		public String getLayersIndexFileLocation() {
 			return "BOOT-INF/layers.idx";
 		}
 
 		@Override
-		public String getRepackagedClassesLocation(Layer layer) {
-			return "BOOT-INF/layers/" + layer + "/classes/";
-		}
-
-		@Override
-		public String getLibraryLocation(String libraryName, LibraryScope scope, Layer layer) {
-			return "BOOT-INF/layers/" + layer + "/lib/";
+		public boolean isExecutable() {
+			return true;
 		}
 
 	}