Use a conventional delegation model in LaunchedURLClassLoader

When an application is run as an executable archive with nested jars,
the application's own classes need to be able to load classes from
within the nested jars. This means that the application's classes need
to be loaded by the same class loader as is used for the nested jars.
When an application is launched with java -jar the contents of the
jar are on the class path of the app class loader, which is the
parent of the LaunchedURLClassLoader that is used to load classes
from within the nested jars. If the root of the jar includes the
application's classes, they would be loaded by the app class loader
and, therefore, would not be able to load classes from within the
nested jars.

Previously, this problem was resolved by LaunchedURLClassLoader being
created with a copy of all of the app class laoder's URLs and by
using an unconventional delegation model that caused it to skip its
parent (the app class loader) and jump straight to its root class
loader. This ensured that the LaunchedURLClassLoader would load both
the application's own classes and those from within any nested jars.
Unfortunately, this unusual delegation model has proved to be
problematic. We have seen and worked around some problems with Java
Agents (see gh-4911 and gh-863), but there are others (see gh-4868)
that cannot be made to work with the current delegation model.

This commit reworks LaunchedURLClassLoader to use a conventional
delegate model with the app class loader as its parent. With this
change in place, the application's own classes need to be hidden
from the app class loader via some other means. This is now achieved
by packaging application classes in BOOT-INF/classes (and, for
symmetry, nested jars are now packaged in BOOT-INF/lib). Both the
JarLauncher and the PropertiesLauncher (which supports the executable
jar layout) have been updated to look for classes and nested jars in
these new locations.

Closes gh-4897
Fixes gh-4868

Author: wilkinsona

spring-boot-cli/pom.xml

@@ -220,7 +220,7 @@
 							<goal>copy-dependencies</goal>
 						</goals>
 						<configuration>
-							<outputDirectory>${project.build.directory}/assembly/lib</outputDirectory>
+							<outputDirectory>${project.build.directory}/assembly/BOOT-INF/lib</outputDirectory>
 							<includeScope>runtime</includeScope>
 						</configuration>
 					</execution>

spring-boot-cli/src/main/assembly/jar-with-dependencies.xml

@@ -15,6 +15,7 @@
 				<include>${project.groupId}:${project.artifactId}</include>
 			</includes>
 			<unpack>true</unpack>
+			<outputDirectory>BOOT-INF/classes/</outputDirectory>
 		</dependencySet>
 	</dependencySets>
 	<fileSets>

spring-boot-cli/src/main/java/org/springframework/boot/cli/archive/PackagedSpringApplicationLauncher.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2014 the original author or authors.
+ * Copyright 2012-2016 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.
@@ -52,7 +52,7 @@ private void run(String[] args) throws Exception {
 	}
 
 	private Object[] getSources(URLClassLoader classLoader) throws Exception {
-		Enumeration<URL> urls = classLoader.findResources("META-INF/MANIFEST.MF");
+		Enumeration<URL> urls = classLoader.getResources("META-INF/MANIFEST.MF");
 		while (urls.hasMoreElements()) {
 			URL url = urls.nextElement();
 			Manifest manifest = new Manifest(url.openStream());

spring-boot-integration-tests/spring-boot-gradle-tests/src/test/java/org/springframework/boot/gradle/MultiProjectRepackagingTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2015 the original author or authors.
+ * Copyright 2012-2016 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.
@@ -42,8 +42,9 @@ public void repackageWithTransitiveFileDependency() throws Exception {
 		File buildLibs = new File(
 				"target/multi-project-transitive-file-dependency/main/build/libs");
 		JarFile jarFile = new JarFile(new File(buildLibs, "main.jar"));
-		assertThat(jarFile.getEntry("lib/commons-logging-1.1.3.jar")).isNotNull();
-		assertThat(jarFile.getEntry("lib/foo.jar")).isNotNull();
+		assertThat(jarFile.getEntry("BOOT-INF/lib/commons-logging-1.1.3.jar"))
+				.isNotNull();
+		assertThat(jarFile.getEntry("BOOT-INF/lib/foo.jar")).isNotNull();
 		jarFile.close();
 	}
 
@@ -57,7 +58,7 @@ public void repackageWithCommonFileDependency() throws Exception {
 				"target/multi-project-common-file-dependency/build/libs");
 		JarFile jarFile = new JarFile(
 				new File(buildLibs, "multi-project-common-file-dependency.jar"));
-		assertThat(jarFile.getEntry("lib/foo.jar")).isNotNull();
+		assertThat(jarFile.getEntry("BOOT-INF/lib/foo.jar")).isNotNull();
 		jarFile.close();
 	}
 
@@ -70,7 +71,7 @@ public void repackageWithRuntimeProjectDependency() throws Exception {
 		File buildLibs = new File(
 				"target/multi-project-runtime-project-dependency/projectA/build/libs");
 		JarFile jarFile = new JarFile(new File(buildLibs, "projectA.jar"));
-		assertThat(jarFile.getEntry("lib/projectB.jar")).isNotNull();
+		assertThat(jarFile.getEntry("BOOT-INF/lib/projectB.jar")).isNotNull();
 		jarFile.close();
 	}
 

spring-boot-integration-tests/spring-boot-gradle-tests/src/test/java/org/springframework/boot/gradle/RepackagingTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2015 the original author or authors.
+ * Copyright 2012-2016 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.
@@ -144,7 +144,7 @@ public void repackageWithFileDependency() throws Exception {
 				.run();
 		File buildLibs = new File("target/repackage/build/libs");
 		JarFile jarFile = new JarFile(new File(buildLibs, "repackage.jar"));
-		assertThat(jarFile.getEntry("lib/foo.jar")).isNotNull();
+		assertThat(jarFile.getEntry("BOOT-INF/lib/foo.jar")).isNotNull();
 		jarFile.close();
 	}
 
@@ -166,7 +166,7 @@ public void repackagingEnabledExcludeDevtools() throws IOException {
 	private boolean isDevToolsJarIncluded(File repackageFile) throws IOException {
 		JarFile jarFile = new JarFile(repackageFile);
 		try {
-			String name = "lib/spring-boot-devtools-" + BOOT_VERSION + ".jar";
+			String name = "BOOT-INF/lib/spring-boot-devtools-" + BOOT_VERSION + ".jar";
 			return jarFile.getEntry(name) != null;
 		}
 		finally {

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2015 the original author or authors.
+ * Copyright 2012-2016 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.
@@ -120,6 +120,11 @@ public void write(OutputStream outputStream) throws IOException {
 	 * @throws IOException if the entries cannot be written
 	 */
 	public void writeEntries(JarFile jarFile) throws IOException {
+		this.writeEntries(jarFile, new IdentityEntryTransformer());
+	}
+
+	void writeEntries(JarFile jarFile, EntryTransformer entryTransformer)
+			throws IOException {
 		Enumeration<JarEntry> entries = jarFile.entries();
 		while (entries.hasMoreElements()) {
 			JarEntry entry = entries.nextElement();
@@ -133,7 +138,7 @@ public void writeEntries(JarFile jarFile) throws IOException {
 							jarFile.getInputStream(entry));
 				}
 				EntryWriter entryWriter = new InputStreamEntryWriter(inputStream, true);
-				writeEntry(entry, entryWriter);
+				writeEntry(entryTransformer.transform(entry), entryWriter);
 			}
 			finally {
 				inputStream.close();
@@ -377,4 +382,25 @@ public void setupStoredEntry(JarEntry entry) {
 		}
 	}
 
+	/**
+	 * An {@code EntryTransformer} enables the transformation of {@link JarEntry jar
+	 * entries} during the writing process.
+	 */
+	interface EntryTransformer {
+
+		JarEntry transform(JarEntry jarEntry);
+	}
+
+	/**
+	 * An {@code EntryTransformer} that returns the entry unchanged.
+	 */
+	private static final class IdentityEntryTransformer implements EntryTransformer {
+
+		@Override
+		public JarEntry transform(JarEntry jarEntry) {
+			return jarEntry;
+		}
+
+	}
+
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2013 the original author or authors.
+ * Copyright 2012-2016 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.
@@ -60,7 +60,7 @@ public static Layout forFile(File file) {
 	/**
 	 * Executable JAR layout.
 	 */
-	public static class Jar implements Layout {
+	public static class Jar implements RepackagingLayout {
 
 		@Override
 		public String getLauncherClassName() {
@@ -69,14 +69,19 @@ public String getLauncherClassName() {
 
 		@Override
 		public String getLibraryDestination(String libraryName, LibraryScope scope) {
-			return "lib/";
+			return "BOOT-INF/lib/";
 		}
 
 		@Override
 		public String getClassesLocation() {
 			return "";
 		}
 
+		@Override
+		public String getRepackagedClassesLocation() {
+			return "BOOT-INF/classes/";
+		}
+
 		@Override
 		public boolean isExecutable() {
 			return true;

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2015 the original author or authors.
+ * Copyright 2012-2016 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.
@@ -24,9 +24,12 @@
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
+import java.util.jar.JarEntry;
 import java.util.jar.JarFile;
 import java.util.jar.Manifest;
 
+import org.springframework.boot.loader.tools.JarWriter.EntryTransformer;
+
 /**
  * Utility class that can be used to repackage an archive so that it can be executed using
  * '{@literal java -jar}'.
@@ -189,7 +192,14 @@ public void library(Library library) throws IOException {
 			writer.writeManifest(buildManifest(sourceJar));
 			Set<String> seen = new HashSet<String>();
 			writeNestedLibraries(unpackLibraries, seen, writer);
-			writer.writeEntries(sourceJar);
+			if (this.layout instanceof RepackagingLayout) {
+				writer.writeEntries(sourceJar,
+						new RenamingEntryTransformer(((RepackagingLayout) this.layout)
+								.getRepackagedClassesLocation()));
+			}
+			else {
+				writer.writeEntries(sourceJar);
+			}
 			writeNestedLibraries(standardLibraries, seen, writer);
 			if (this.layout.isExecutable()) {
 				writer.writeLoaderClasses();
@@ -293,4 +303,47 @@ private void deleteFile(File file) {
 		}
 	}
 
+	/**
+	 * An {@code EntryTransformer} that renames entries by applying a prefix.
+	 */
+	private static final class RenamingEntryTransformer implements EntryTransformer {
+
+		private final String namePrefix;
+
+		private RenamingEntryTransformer(String namePrefix) {
+			this.namePrefix = namePrefix;
+		}
+
+		@Override
+		public JarEntry transform(JarEntry entry) {
+			if (entry.getName().startsWith("META-INF/")
+					|| entry.getName().startsWith("BOOT-INF/")) {
+				return entry;
+			}
+			JarEntry renamedEntry = new JarEntry(this.namePrefix + entry.getName());
+			renamedEntry.setTime(entry.getTime());
+			renamedEntry.setSize(entry.getSize());
+			renamedEntry.setMethod(entry.getMethod());
+			if (entry.getComment() != null) {
+				renamedEntry.setComment(entry.getComment());
+			}
+			renamedEntry.setCompressedSize(entry.getCompressedSize());
+			renamedEntry.setCrc(entry.getCrc());
+			if (entry.getCreationTime() != null) {
+				renamedEntry.setCreationTime(entry.getCreationTime());
+			}
+			if (entry.getExtra() != null) {
+				renamedEntry.setExtra(entry.getExtra());
+			}
+			if (entry.getLastAccessTime() != null) {
+				renamedEntry.setLastAccessTime(entry.getLastAccessTime());
+			}
+			if (entry.getLastModifiedTime() != null) {
+				renamedEntry.setLastModifiedTime(entry.getLastModifiedTime());
+			}
+			return renamedEntry;
+		}
+
+	}
+
 }

spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/JavaAgentDetector.java renamed to spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/RepackagingLayout.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2015 the original author or authors.
+ * Copyright 2012-2016 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.
@@ -14,24 +14,21 @@
  * limitations under the License.
  */
 
-package org.springframework.boot.loader;
-
-import java.net.URL;
+package org.springframework.boot.loader.tools;
 
 /**
- * A strategy for detecting Java agents.
+ * A specialization of {@link Layout} that repackages an existing archive by moving its
+ * content to a new location.
  *
  * @author Andy Wilkinson
- * @since 1.1.0
+ * @since 1.4.0
  */
-public interface JavaAgentDetector {
+public interface RepackagingLayout extends Layout {
 
 	/**
-	 * Returns {@code true} if {@code url} points to a Java agent jar file, otherwise
-	 * {@code false} is returned.
-	 * @param url The url to examine
-	 * @return if the URL points to a Java agent
+	 * Returns the location to which classes should be moved.
+	 * @return the repackaged classes location
 	 */
-	boolean isJavaAgentJar(URL url);
+	String getRepackagedClassesLocation();
 
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2013 the original author or authors.
+ * Copyright 2012-2016 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.
@@ -64,13 +64,13 @@ public void unknownFile() throws Exception {
 	public void jarLayout() throws Exception {
 		Layout layout = new Layouts.Jar();
 		assertThat(layout.getLibraryDestination("lib.jar", LibraryScope.COMPILE))
-				.isEqualTo("lib/");
+				.isEqualTo("BOOT-INF/lib/");
 		assertThat(layout.getLibraryDestination("lib.jar", LibraryScope.CUSTOM))
-				.isEqualTo("lib/");
+				.isEqualTo("BOOT-INF/lib/");
 		assertThat(layout.getLibraryDestination("lib.jar", LibraryScope.PROVIDED))
-				.isEqualTo("lib/");
+				.isEqualTo("BOOT-INF/lib/");
 		assertThat(layout.getLibraryDestination("lib.jar", LibraryScope.RUNTIME))
-				.isEqualTo("lib/");
+				.isEqualTo("BOOT-INF/lib/");
 	}
 
 	@Test