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 <pwebb@pivotal.io>

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

@@ -20,8 +20,11 @@ import java.io.ByteArrayOutputStream;
 import java.io.File;
 import java.io.FileOutputStream;
 import java.io.IOException;
+import java.io.OutputStreamWriter;
+import java.io.Writer;
 import java.net.MalformedURLException;
 import java.net.URL;
+import java.nio.charset.StandardCharsets;
 import java.util.Enumeration;
 import java.util.LinkedHashSet;
 import java.util.List;
@@ -41,6 +44,7 @@ import org.springframework.util.FileCopyUtils;
  * Base class for testing {@link ExecutableArchiveLauncher} implementations.
  *
  * @author Andy Wilkinson
+ * @author Madhura Bhave
  */
 public abstract class AbstractExecutableArchiveLauncherTests {
 
@@ -48,11 +52,25 @@ public abstract class AbstractExecutableArchiveLauncherTests {
 	File tempDir;
 
 	protected File createJarArchive(String name, String entryPrefix) throws IOException {
+		return createJarArchive(name, entryPrefix, false);
+	}
+
+	@SuppressWarnings("resource")
+	protected File createJarArchive(String name, String entryPrefix, boolean indexed) throws IOException {
 		File archive = new File(this.tempDir, name);
 		JarOutputStream jarOutputStream = new JarOutputStream(new FileOutputStream(archive));
 		jarOutputStream.putNextEntry(new JarEntry(entryPrefix + "/"));
 		jarOutputStream.putNextEntry(new JarEntry(entryPrefix + "/classes/"));
 		jarOutputStream.putNextEntry(new JarEntry(entryPrefix + "/lib/"));
+		if (indexed) {
+			JarEntry indexEntry = new JarEntry(entryPrefix + "/classpath.idx");
+			jarOutputStream.putNextEntry(indexEntry);
+			Writer writer = new OutputStreamWriter(jarOutputStream, StandardCharsets.UTF_8);
+			writer.write("BOOT-INF/lib/foo.jar\n");
+			writer.write("BOOT-INF/lib/bar.jar\n");
+			writer.write("BOOT-INF/lib/baz.jar\n");
+			writer.flush();
+		}
 		addNestedJars(entryPrefix, "/lib/foo.jar", jarOutputStream);
 		addNestedJars(entryPrefix, "/lib/bar.jar", jarOutputStream);
 		addNestedJars(entryPrefix, "/lib/baz.jar", jarOutputStream);

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

@@ -0,0 +1,123 @@
+/*
+ * 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.File;
+import java.io.IOException;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.nio.file.Files;
+import java.util.ArrayList;
+import java.util.List;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
+
+/**
+ * Tests for {@link ClassPathIndexFile}.
+ *
+ * @author Madhura Bhave
+ * @author Phillip Webb
+ */
+class ClassPathIndexFileTests {
+
+	@TempDir
+	File temp;
+
+	@Test
+	void loadIfPossibleWhenRootIsNotFileReturnsNull() throws IOException {
+		assertThatIllegalArgumentException()
+				.isThrownBy(() -> ClassPathIndexFile.loadIfPossible(new URL("https://example.com/file"), "test.idx"))
+				.withMessage("URL does not reference a file");
+	}
+
+	@Test
+	void loadIfPossibleWhenRootDoesNotExistReturnsNull() throws Exception {
+		File root = new File(this.temp, "missing");
+		assertThat(ClassPathIndexFile.loadIfPossible(root.toURI().toURL(), "test.idx")).isNull();
+	}
+
+	@Test
+	void loadIfPossibleWhenRootIsFolderThrowsException() throws Exception {
+		File root = new File(this.temp, "folder");
+		root.mkdirs();
+		assertThat(ClassPathIndexFile.loadIfPossible(root.toURI().toURL(), "test.idx")).isNull();
+	}
+
+	@Test
+	void loadIfPossibleReturnsInstance() throws Exception {
+		ClassPathIndexFile indexFile = copyAndLoadTestIndexFile();
+		assertThat(indexFile).isNotNull();
+	}
+
+	@Test
+	void sizeReturnsNumberOfLines() throws Exception {
+		ClassPathIndexFile indexFile = copyAndLoadTestIndexFile();
+		assertThat(indexFile.size()).isEqualTo(5);
+	}
+
+	@Test
+	void containsFolderWhenFolderIsPresentReturnsTrue() throws Exception {
+		ClassPathIndexFile indexFile = copyAndLoadTestIndexFile();
+		assertThat(indexFile.containsFolder("BOOT-INF/layers/one/lib")).isTrue();
+		assertThat(indexFile.containsFolder("BOOT-INF/layers/one/lib/")).isTrue();
+		assertThat(indexFile.containsFolder("BOOT-INF/layers/two/lib")).isTrue();
+	}
+
+	@Test
+	void containsFolderWhenFolderIsMissingReturnsFalse() throws Exception {
+		ClassPathIndexFile indexFile = copyAndLoadTestIndexFile();
+		assertThat(indexFile.containsFolder("BOOT-INF/layers/nope/lib/")).isFalse();
+	}
+
+	@Test
+	void getUrlsReturnsUrls() throws Exception {
+		ClassPathIndexFile indexFile = copyAndLoadTestIndexFile();
+		List<URL> urls = indexFile.getUrls();
+		List<File> expected = new ArrayList<>();
+		expected.add(new File(this.temp, "BOOT-INF/layers/one/lib/a.jar"));
+		expected.add(new File(this.temp, "BOOT-INF/layers/one/lib/b.jar"));
+		expected.add(new File(this.temp, "BOOT-INF/layers/one/lib/c.jar"));
+		expected.add(new File(this.temp, "BOOT-INF/layers/two/lib/d.jar"));
+		expected.add(new File(this.temp, "BOOT-INF/layers/two/lib/e.jar"));
+		assertThat(urls).containsExactly(expected.stream().map(this::toUrl).toArray(URL[]::new));
+	}
+
+	private URL toUrl(File file) {
+		try {
+			return file.toURI().toURL();
+		}
+		catch (MalformedURLException ex) {
+			throw new IllegalStateException(ex);
+		}
+	}
+
+	private ClassPathIndexFile copyAndLoadTestIndexFile() throws IOException, MalformedURLException {
+		copyTestIndexFile();
+		ClassPathIndexFile indexFile = ClassPathIndexFile.loadIfPossible(this.temp.toURI().toURL(), "test.idx");
+		return indexFile;
+	}
+
+	private void copyTestIndexFile() throws IOException {
+		Files.copy(getClass().getResourceAsStream("classpath-index-file.idx"),
+				new File(this.temp, "test.idx").toPath());
+	}
+
+}

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

@@ -18,7 +18,9 @@ package org.springframework.boot.loader;
 
 import java.io.File;
 import java.net.URL;
+import java.net.URLClassLoader;
 import java.util.ArrayList;
+import java.util.Iterator;
 import java.util.List;
 
 import org.junit.jupiter.api.Test;
@@ -33,6 +35,7 @@ import static org.assertj.core.api.Assertions.assertThat;
  * Tests for {@link JarLauncher}.
  *
  * @author Andy Wilkinson
+ * @author Madhura Bhave
  */
 class JarLauncherTests extends AbstractExecutableArchiveLauncherTests {
 
@@ -67,6 +70,16 @@ class JarLauncherTests extends AbstractExecutableArchiveLauncherTests {
 		}
 	}
 
+	@Test
+	void explodedJarShouldPreserveClasspathOrderWhenIndexPresent() throws Exception {
+		File explodedRoot = explode(createJarArchive("archive.jar", "BOOT-INF", true));
+		JarLauncher launcher = new JarLauncher(new ExplodedArchive(explodedRoot, true));
+		Iterator<Archive> archives = launcher.getClassPathArchivesIterator();
+		URLClassLoader classLoader = (URLClassLoader) launcher.createClassLoader(archives);
+		URL[] urls = classLoader.getURLs();
+		assertThat(urls).containsExactly(getExpectedFileUrls(explodedRoot));
+	}
+
 	protected final URL[] getExpectedFileUrls(File explodedRoot) {
 		return getExpectedFiles(explodedRoot).stream().map(this::toUrl).toArray(URL[]::new);
 	}

spring-boot-project/spring-boot-tools/spring-boot-loader/src/test/resources/org/springframework/boot/loader/classpath-index-file.idx

@@ -0,0 +1,5 @@
+BOOT-INF/layers/one/lib/a.jar
+BOOT-INF/layers/one/lib/b.jar
+BOOT-INF/layers/one/lib/c.jar
+BOOT-INF/layers/two/lib/d.jar
+BOOT-INF/layers/two/lib/e.jar