Add classpath index support for exploded archives

Update the `Repackager` class so that an additional `classpath.idx` file
is written into the jar that provides the original order of the
classpath. The `JarLauncher` class now uses this file when running as
an exploded archive to ensure that the classpath order is the same as
when running from the far jar.

Closes gh-9128

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/JarWriter.java

@@ -17,6 +17,7 @@
 package org.springframework.boot.loader.tools;
 
 import java.io.BufferedInputStream;
+import java.io.BufferedWriter;
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.File;
@@ -27,13 +28,16 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.io.OutputStreamWriter;
 import java.net.URL;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.attribute.PosixFilePermission;
 import java.util.Arrays;
 import java.util.Enumeration;
 import java.util.HashSet;
+import java.util.List;
 import java.util.Set;
 import java.util.jar.JarEntry;
 import java.util.jar.JarFile;
@@ -52,6 +56,7 @@
  *
  * @author Phillip Webb
  * @author Andy Wilkinson
+ * @author Madhura Bhave
  * @since 1.0.0
  */
 public class JarWriter implements LoaderClassesWriter, AutoCloseable {
@@ -190,6 +195,28 @@ public void writeNestedLibrary(String destination, Library library) throws IOExc
 		}
 	}
 
+	/**
+	 * Write a simple index file containing the specified UTF-8 lines.
+	 * @param location the location of the index file
+	 * @param lines the lines to write
+	 * @throws IOException if the write fails
+	 * @since 2.3.0
+	 */
+	public void writeIndexFile(String location, List<String> lines) throws IOException {
+		if (location != null) {
+			JarArchiveEntry entry = new JarArchiveEntry(location);
+			writeEntry(entry, (outputStream) -> {
+				BufferedWriter writer = new BufferedWriter(
+						new OutputStreamWriter(outputStream, StandardCharsets.UTF_8));
+				for (String line : lines) {
+					writer.write(line);
+					writer.write("\n");
+				}
+				writer.flush();
+			});
+		}
+	}
+
 	private long getNestedLibraryTime(File file) {
 		try {
 			try (JarFile jarFile = new JarFile(file)) {

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

@@ -28,6 +28,7 @@
  * @author Phillip Webb
  * @author Dave Syer
  * @author Andy Wilkinson
+ * @author Madhura Bhave
  * @since 1.0.0
  */
 public final class Layouts {
@@ -88,6 +89,11 @@ public String getRepackagedClassesLocation() {
 			return "BOOT-INF/classes/";
 		}
 
+		@Override
+		public String getClasspathIndexFileLocation() {
+			return "BOOT-INF/classpath.idx";
+		}
+
 		@Override
 		public boolean isExecutable() {
 			return true;

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

@@ -45,6 +45,7 @@
  * @author Phillip Webb
  * @author Andy Wilkinson
  * @author Stephane Nicoll
+ * @author Madhura Bhave
  * @since 1.0.0
  */
 public class Repackager {
@@ -59,6 +60,8 @@ public class Repackager {
 
 	private static final String BOOT_LIB_ATTRIBUTE = "Spring-Boot-Lib";
 
+	private static final String BOOT_CLASSPATH_INDEX_ATTRIBUTE = "Spring-Boot-Classpath-Index";
+
 	private static final byte[] ZIP_FILE_HEADER = new byte[] { 'P', 'K', 3, 4 };
 
 	private static final long FIND_WARNING_TIMEOUT = TimeUnit.SECONDS.toMillis(10);
@@ -336,6 +339,7 @@ private void addBootAttributes(Attributes attributes) {
 	private void addBootBootAttributesForRepackagingLayout(Attributes attributes, RepackagingLayout layout) {
 		attributes.putValue(BOOT_CLASSES_ATTRIBUTE, layout.getRepackagedClassesLocation());
 		putIfHasLength(attributes, BOOT_LIB_ATTRIBUTE, this.layout.getLibraryLocation("", LibraryScope.COMPILE));
+		putIfHasLength(attributes, BOOT_CLASSPATH_INDEX_ATTRIBUTE, layout.getClasspathIndexFileLocation());
 	}
 
 	private void addBootBootAttributesForPlainLayout(Attributes attributes, Layout layout) {
@@ -473,6 +477,10 @@ private void write(JarWriter writer) throws IOException {
 				writer.writeNestedLibrary(entry.getKey().substring(0, entry.getKey().lastIndexOf('/') + 1),
 						entry.getValue());
 			}
+			if (Repackager.this.layout instanceof RepackagingLayout) {
+				String location = ((RepackagingLayout) (Repackager.this.layout)).getClasspathIndexFileLocation();
+				writer.writeIndexFile(location, new ArrayList<>(this.libraryEntryNames.keySet()));
+			}
 		}
 
 	}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * 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.
@@ -31,4 +31,15 @@ public interface RepackagingLayout extends Layout {
 	 */
 	String getRepackagedClassesLocation();
 
+	/**
+	 * Returns the location of the classpath index file that should be written or
+	 * {@code null} if not index is required. The result should include the filename and
+	 * is relative to the root of the jar.
+	 * @return the classpath index file location
+	 * @since 2.3.0
+	 */
+	default String getClasspathIndexFileLocation() {
+		return null;
+	}
+
 }

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

@@ -18,11 +18,14 @@
 
 import java.io.ByteArrayInputStream;
 import java.io.File;
+import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.IOException;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.attribute.PosixFilePermission;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Calendar;
 import java.util.Enumeration;
 import java.util.List;
@@ -45,6 +48,7 @@
 import org.springframework.boot.loader.tools.sample.ClassWithMainMethod;
 import org.springframework.boot.loader.tools.sample.ClassWithoutMainMethod;
 import org.springframework.util.FileCopyUtils;
+import org.springframework.util.StreamUtils;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
@@ -59,6 +63,7 @@
  *
  * @author Phillip Webb
  * @author Andy Wilkinson
+ * @author Madhura Bhave
  */
 class RepackagerTests {
 
@@ -299,6 +304,34 @@ void libraries() throws Exception {
 		assertThat(entry.getComment()).hasSize(47);
 	}
 
+	@Test
+	void index() throws Exception {
+		TestJarFile libJar1 = new TestJarFile(this.tempDir);
+		libJar1.addClass("a/b/C.class", ClassWithoutMainMethod.class, JAN_1_1985);
+		File libJarFile1 = libJar1.getFile();
+		TestJarFile libJar2 = new TestJarFile(this.tempDir);
+		libJar2.addClass("a/b/C.class", ClassWithoutMainMethod.class, JAN_1_1985);
+		File libJarFile2 = libJar2.getFile();
+		TestJarFile libJar3 = new TestJarFile(this.tempDir);
+		libJar3.addClass("a/b/C.class", ClassWithoutMainMethod.class, JAN_1_1985);
+		File libJarFile3 = libJar3.getFile();
+		this.testJarFile.addClass("a/b/C.class", ClassWithMainMethod.class);
+		File file = this.testJarFile.getFile();
+		Repackager repackager = new Repackager(file);
+		repackager.repackage((callback) -> {
+			callback.library(new Library(libJarFile1, LibraryScope.COMPILE));
+			callback.library(new Library(libJarFile2, LibraryScope.COMPILE));
+			callback.library(new Library(libJarFile3, LibraryScope.COMPILE));
+		});
+		assertThat(hasEntry(file, "BOOT-INF/classpath.idx")).isTrue();
+		ZipUtil.unpack(file, new File(file.getParent()));
+		FileInputStream inputStream = new FileInputStream(new File(file.getParent() + "/BOOT-INF/classpath.idx"));
+		String index = StreamUtils.copyToString(inputStream, StandardCharsets.UTF_8);
+		String[] libraries = index.split("\\r?\\n");
+		assertThat(Arrays.asList(libraries)).contains("BOOT-INF/lib/" + libJarFile1.getName(),
+				"BOOT-INF/lib/" + libJarFile2.getName(), "BOOT-INF/lib/" + libJarFile3.getName());
+	}
+
 	@Test
 	void duplicateLibraries() throws Exception {
 		TestJarFile libJar = new TestJarFile(this.tempDir);

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

@@ -0,0 +1,130 @@
+/*
+ * 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;
+
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.net.MalformedURLException;
+import java.net.URISyntaxException;
+import java.net.URL;
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Objects;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+/**
+ * A class path index file that provides ordering information for JARs.
+ *
+ * @author Madhura Bhave
+ * @author Phillip Webb
+ */
+final class ClassPathIndexFile {
+
+	private final File root;
+
+	private final List<String> lines;
+
+	private final Set<String> folders;
+
+	private ClassPathIndexFile(File root, List<String> lines) {
+		this.root = root;
+		this.lines = lines;
+		this.folders = this.lines.stream().map(this::getFolder).filter(Objects::nonNull).collect(Collectors.toSet());
+	}
+
+	private String getFolder(String name) {
+		int lastSlash = name.lastIndexOf("/");
+		return (lastSlash != -1) ? name.substring(0, lastSlash) : null;
+	}
+
+	int size() {
+		return this.lines.size();
+	}
+
+	boolean containsFolder(String name) {
+		if (name == null || name.isEmpty()) {
+			return false;
+		}
+		if (name.endsWith("/")) {
+			return containsFolder(name.substring(0, name.length() - 1));
+		}
+		return this.folders.contains(name);
+	}
+
+	List<URL> getUrls() {
+		return Collections.unmodifiableList(this.lines.stream().map(this::asUrl).collect(Collectors.toList()));
+	}
+
+	private URL asUrl(String line) {
+		try {
+			return new File(this.root, line).toURI().toURL();
+		}
+		catch (MalformedURLException ex) {
+			throw new IllegalStateException(ex);
+		}
+	}
+
+	static ClassPathIndexFile loadIfPossible(URL root, String location) throws IOException {
+		return loadIfPossible(asFile(root), location);
+	}
+
+	private static ClassPathIndexFile loadIfPossible(File root, String location) throws IOException {
+		return loadIfPossible(root, new File(root, location));
+	}
+
+	private static ClassPathIndexFile loadIfPossible(File root, File indexFile) throws IOException {
+		if (indexFile.exists() && indexFile.isFile()) {
+			try (InputStream inputStream = new FileInputStream(indexFile)) {
+				return new ClassPathIndexFile(root, loadLines(inputStream));
+			}
+		}
+		return null;
+	}
+
+	private static List<String> loadLines(InputStream inputStream) throws IOException {
+		List<String> lines = new ArrayList<>();
+		BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, StandardCharsets.UTF_8));
+		String line = reader.readLine();
+		while (line != null) {
+			if (!line.trim().isEmpty()) {
+				lines.add(line);
+			}
+			line = reader.readLine();
+		}
+		return Collections.unmodifiableList(lines);
+	}
+
+	private static File asFile(URL url) {
+		if (!"file".equals(url.getProtocol())) {
+			throw new IllegalArgumentException("URL does not reference a file");
+		}
+		try {
+			return new File(url.toURI());
+		}
+		catch (URISyntaxException ex) {
+			return new File(url.getPath());
+		}
+	}
+
+}