Allow `new URL(String)` with nested JARs

Update JarFile to allow the custom registration of a JAR
`URLStreamHandler` that allows `jar:` URLs to be constructed from
Strings. This removes the previous requirement that all nested JAR URLs
be created with a 'context'.

To supported nested JARs the `java.protocol.handler.pkgs` system
property is changed so that our custom URLHandler is picked for 'jar'
protocols in preference to the Java default.

Fixes gh-269

spring-boot-tools/spring-boot-loader/README.md

@@ -162,25 +162,6 @@ $ java org.springframework.boot.loader.JarLauncher
 There are a number of restrictions that you need to consider when working with a Spring
 Boot Loader packaged application.
 
-### URLs
-URLs for nested jar entries intentionally look and behave like standard jar URLs,
-You cannot, however, directly create a nested jar URL from a string:
-
-```
-URL url = classLoader.getResoure("/a/b.txt");
-String s = url.toString(); // In the form 'jar:file:/file.jar!/nested.jar!/a/b.txt'
-new URL(s); // This will fail
-```
-
-If you need to obtain URL using a String, ensure that you always provide a context URL
-to the constructor. This will ensure that the custom `URLStreamHandler` used to support
-nested jars is used.
-
-```
-URL url = classLoader.getResoure("/a");
-new URL(url, "b.txt");
-```
-
 ### Zip entry compression
 The `ZipEntry` for a nested jar must be saved using the `ZipEntry.STORED` method. This
 is required so that we can seek directly to individual content within the nested jar.

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2013 the original author or authors.
+ * Copyright 2012-2014 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.
@@ -23,6 +23,7 @@ import java.util.List;
 import java.util.logging.Logger;
 
 import org.springframework.boot.loader.archive.Archive;
+import org.springframework.boot.loader.jar.JarFile;
 
 /**
  * Base class for launchers that can start an application with a fully configured
@@ -49,6 +50,7 @@ public abstract class Launcher {
 	 */
 	protected void launch(String[] args) {
 		try {
+			JarFile.registerUrlProtocolHandler();
 			ClassLoader classLoader = createClassLoader(getClassPathArchives());
 			launch(args, getMainClass(), classLoader);
 		}

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

@@ -0,0 +1,93 @@
+/*
+ * Copyright 2012-2014 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
+ *
+ *      http://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.jar;
+
+import java.io.File;
+import java.io.IOException;
+import java.net.MalformedURLException;
+import java.net.URISyntaxException;
+import java.net.URL;
+import java.net.URLConnection;
+import java.net.URLStreamHandler;
+
+/**
+ * {@link URLStreamHandler} for Spring Boot loader {@link JarFile}s.
+ * 
+ * @author Phillip Webb
+ * @see JarFile#registerUrlProtocolHandler()
+ */
+public class Handler extends URLStreamHandler {
+
+	// NOTE: in order to be found as a URL protocol hander, this class must be public,
+	// must be named Handler and must be in a package ending '.jar'
+
+	private static final String SEPARATOR = JarURLConnection.SEPARATOR;
+
+	private final JarFile jarFile;
+
+	public Handler() {
+		this(null);
+	}
+
+	public Handler(JarFile jarFile) {
+		this.jarFile = jarFile;
+	}
+
+	@Override
+	protected URLConnection openConnection(URL url) throws IOException {
+		JarFile jarFile = (this.jarFile != null ? this.jarFile : getJarFileFromUrl(url));
+		return new JarURLConnection(url, jarFile);
+	}
+
+	public JarFile getJarFileFromUrl(URL url) throws IOException {
+
+		String spec = url.getFile();
+
+		int separatorIndex = spec.indexOf(SEPARATOR);
+		if (separatorIndex == -1) {
+			throw new MalformedURLException("Jar URL does not contain !/ separator");
+		}
+
+		JarFile jar = null;
+		while (separatorIndex != -1) {
+			String name = spec.substring(0, separatorIndex);
+			jar = (jar == null ? getRootJarFile(name) : getNestedJarFile(jar, name));
+			spec = spec.substring(separatorIndex + SEPARATOR.length());
+			separatorIndex = spec.indexOf(SEPARATOR);
+		}
+
+		return jar;
+	}
+
+	private JarFile getRootJarFile(String name) throws IOException {
+		try {
+			return new JarFile(new File(new URL(name).toURI()));
+		}
+		catch (URISyntaxException ex) {
+			throw new IOException("Unable to open root Jar file '" + name + "'", ex);
+		}
+	}
+
+	private JarFile getNestedJarFile(JarFile jarFile, String name) throws IOException {
+		JarEntry jarEntry = jarFile.getJarEntry(name);
+		if (jarEntry == null) {
+			throw new IOException("Unable to find nested jar '" + name + "' from '"
+					+ jarFile + "'");
+		}
+		return jarFile.getNestedJarFile(jarEntry);
+	}
+}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2013 the original author or authors.
+ * Copyright 2012-2014 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.
@@ -17,6 +17,8 @@
 package org.springframework.boot.loader.jar;
 
 import java.io.IOException;
+import java.net.MalformedURLException;
+import java.net.URL;
 import java.security.CodeSigner;
 import java.security.cert.Certificate;
 import java.util.jar.Attributes;
@@ -47,6 +49,13 @@ public class JarEntry extends java.util.jar.JarEntry {
 		return this.source;
 	}
 
+	/**
+	 * Return a {@link URL} for this {@link JarEntry}.
+	 */
+	public URL getUrl() throws MalformedURLException {
+		return new URL(this.source.getSource().getUrl(), getName());
+	}
+
 	@Override
 	public Attributes getAttributes() throws IOException {
 		Manifest manifest = this.source.getSource().getManifest();

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2013 the original author or authors.
+ * Copyright 2012-2014 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.
@@ -22,6 +22,8 @@ import java.io.InputStream;
 import java.lang.ref.SoftReference;
 import java.net.MalformedURLException;
 import java.net.URL;
+import java.net.URLStreamHandler;
+import java.net.URLStreamHandlerFactory;
 import java.util.ArrayList;
 import java.util.Enumeration;
 import java.util.HashMap;
@@ -63,6 +65,10 @@ public class JarFile extends java.util.jar.JarFile implements Iterable<JarEntryD
 
 	private static final AsciiBytes SIGNATURE_FILE_EXTENSION = new AsciiBytes(".SF");
 
+	private static final String PROTOCOL_HANDLER = "java.protocol.handler.pkgs";
+
+	private static final String HANDLERS_PACKAGE = "org.springframework.boot.loader";
+
 	private final RandomAccessDataFile rootFile;
 
 	private final RandomAccessData data;
@@ -380,8 +386,32 @@ public class JarFile extends java.util.jar.JarFile implements Iterable<JarEntryD
 	 * @throws MalformedURLException
 	 */
 	public URL getUrl() throws MalformedURLException {
-		JarURLStreamHandler handler = new JarURLStreamHandler(this);
+		Handler handler = new Handler(this);
 		return new URL("jar", "", -1, "file:" + getName() + "!/", handler);
 	}
 
+	/**
+	 * Register a {@literal 'java.protocol.handler.pkgs'} property so that a
+	 * {@link URLStreamHandler} will be located to deal with jar URLs.
+	 */
+	public static void registerUrlProtocolHandler() {
+		String handlers = System.getProperty(PROTOCOL_HANDLER);
+		System.setProperty(PROTOCOL_HANDLER, ("".equals(handlers) ? HANDLERS_PACKAGE
+				: handlers + "|" + HANDLERS_PACKAGE));
+		resetCachedUrlHandlers();
+	}
+
+	/**
+	 * Reset any cached handers just in case a jar protocol has already been used. We
+	 * reset the handler by trying to set a null {@link URLStreamHandlerFactory} which
+	 * should have no effect other than clearing the handlers cache.
+	 */
+	private static void resetCachedUrlHandlers() {
+		try {
+			URL.setURLStreamHandlerFactory(null);
+		}
+		catch (Error ex) {
+			// Ignore
+		}
+	}
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2013 the original author or authors.
+ * Copyright 2012-2014 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.
@@ -29,9 +29,11 @@ import java.net.URL;
  */
 class JarURLConnection extends java.net.JarURLConnection {
 
-	private static final String JAR_URL_POSTFIX = "!/";
+	static final String PROTOCOL = "jar";
 
-	private static final String JAR_URL_PREFIX = "jar:file:";
+	static final String SEPARATOR = "!/";
+
+	private static final String PREFIX = PROTOCOL + ":" + "file:";
 
 	private final JarFile jarFile;
 
@@ -46,9 +48,10 @@ class JarURLConnection extends java.net.JarURLConnection {
 		this.jarFile = jarFile;
 
 		String spec = url.getFile();
-		int separator = spec.lastIndexOf(JAR_URL_POSTFIX);
+		int separator = spec.lastIndexOf(SEPARATOR);
 		if (separator == -1) {
-			throw new MalformedURLException("no !/ found in url spec:" + spec);
+			throw new MalformedURLException("no " + SEPARATOR + " found in url spec:"
+					+ spec);
 		}
 		if (separator + 2 != spec.length()) {
 			this.jarEntryName = spec.substring(separator + 2);
@@ -122,11 +125,11 @@ class JarURLConnection extends java.net.JarURLConnection {
 
 	private static String buildRootUrl(JarFile jarFile) {
 		String path = jarFile.getRootJarFile().getFile().getPath();
-		StringBuilder builder = new StringBuilder(JAR_URL_PREFIX.length() + path.length()
+		StringBuilder builder = new StringBuilder(PREFIX.length() + path.length()
-				+ JAR_URL_POSTFIX.length());
+				+ SEPARATOR.length());
-		builder.append(JAR_URL_PREFIX);
+		builder.append(PREFIX);
 		builder.append(path);
-		builder.append(JAR_URL_POSTFIX);
+		builder.append(SEPARATOR);
 		return builder.toString();
 	}
 

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

@@ -1,41 +0,0 @@
-/*
- * Copyright 2012-2013 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
- *
- *      http://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.jar;
-
-import java.io.IOException;
-import java.net.URL;
-import java.net.URLConnection;
-import java.net.URLStreamHandler;
-
-/**
- * {@link URLStreamHandler} used to support {@link JarFile#getUrl()}.
- * 
- * @author Phillip Webb
- */
-class JarURLStreamHandler extends URLStreamHandler {
-
-	private final JarFile jarFile;
-
-	public JarURLStreamHandler(JarFile jarFile) {
-		this.jarFile = jarFile;
-	}
-
-	@Override
-	protected URLConnection openConnection(URL url) throws IOException {
-		return new JarURLConnection(url, this.jarFile);
-	}
-}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2013 the original author or authors.
+ * Copyright 2012-2014 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.
@@ -51,7 +51,7 @@ import static org.mockito.Mockito.verify;
  * 
  * @author Phillip Webb
  */
-public class RandomAccessJarFileTests {
+public class JarFileTests {
 
 	@Rule
 	public ExpectedException thrown = ExpectedException.none();
@@ -153,7 +153,7 @@ public class RandomAccessJarFileTests {
 	}
 
 	@Test
-	public void getEntryUrl() throws Exception {
+	public void createEntryUrl() throws Exception {
 		URL url = new URL(this.jarFile.getUrl(), "1.dat");
 		assertThat(url.toString(), equalTo("jar:file:" + this.rootJarFile.getPath()
 				+ "!/1.dat"));
@@ -237,6 +237,29 @@ public class RandomAccessJarFileTests {
 				sameInstance(nestedJarFile));
 	}
 
+	@Test
+	public void getNestJarEntryUrl() throws Exception {
+		JarFile nestedJarFile = this.jarFile.getNestedJarFile(this.jarFile
+				.getEntry("nested.jar"));
+		URL url = nestedJarFile.getJarEntry("3.dat").getUrl();
+		assertThat(url.toString(), equalTo("jar:file:" + this.rootJarFile.getPath()
+				+ "!/nested.jar!/3.dat"));
+		InputStream inputStream = url.openStream();
+		assertThat(inputStream, notNullValue());
+		assertThat(inputStream.read(), equalTo(3));
+	}
+
+	@Test
+	public void createUrlFromString() throws Exception {
+		JarFile.registerUrlProtocolHandler();
+		String spec = "jar:file:" + this.rootJarFile.getPath() + "!/nested.jar!/3.dat";
+		URL url = new URL(spec);
+		assertThat(url.toString(), equalTo(spec));
+		InputStream inputStream = url.openStream();
+		assertThat(inputStream, notNullValue());
+		assertThat(inputStream.read(), equalTo(3));
+	}
+
 	@Test
 	public void getDirectoryInputStream() throws Exception {
 		InputStream inputStream = this.jarFile