Special case for root of classpath resource in archive

This turns out to affect JPA, but only because it looks for a URL for the
root of the classpath using ClassLoader.getResource("") which barfs in
an app launched from an executable JAR. It's easy to make a special case
for "" in the class loader, so I went ahead and did that. Possibly need
to think what the implication of getResources("") is as well (not
tested in an app yet).

Fixes gh-420

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

@@ -21,6 +21,8 @@ import java.net.URL;
 import java.net.URLClassLoader;
 import java.security.AccessController;
 import java.security.PrivilegedExceptionAction;
+import java.util.Arrays;
+import java.util.Collections;
 import java.util.Enumeration;
 
 import org.springframework.boot.loader.jar.JarFile;
@@ -63,6 +65,28 @@ public class LaunchedURLClassLoader extends URLClassLoader {
 		return (url == null ? findResource(name) : url);
 	}
 
+	@Override
+	public URL findResource(String name) {
+		if (name.equals("")) {
+			URL[] urls = getURLs();
+			if (urls.length > 0) {
+				return urls[0];
+			}
+		}
+		return super.findResource(name);
+	}
+
+	@Override
+	public Enumeration<URL> findResources(String name) throws IOException {
+		if (name.equals("")) {
+			URL[] urls = getURLs();
+			if (urls.length > 0) {
+				return Collections.enumeration(Arrays.asList(urls));
+			}
+		}
+		return super.findResources(name);
+	}
+
 	@Override
 	public Enumeration<URL> getResources(String name) throws IOException {
 

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

@@ -75,6 +75,8 @@ public abstract class Launcher {
 	protected ClassLoader createClassLoader(List<Archive> archives) throws Exception {
 		List<URL> urls = new ArrayList<URL>(archives.size());
 		for (Archive archive : archives) {
+			// Add the current archive at end (it will be reversed and end up taking
+			// precedence)
 			urls.add(archive.getUrl());
 		}
 		return createClassLoader(urls.toArray(new URL[urls.size()]));

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

@@ -0,0 +1,63 @@
+/*
+ * 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;
+
+import java.net.URL;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+
+/**
+ * @author Dave Syer
+ */
+public class LaunchedURLClassLoaderTests {
+
+	@Test
+	public void resolveResourceFromArchive() throws Exception {
+		LaunchedURLClassLoader loader = new LaunchedURLClassLoader(new URL[] { new URL(
+				"jar:file:src/test/resources/jars/app.jar!/") }, getClass()
+				.getClassLoader());
+		assertNotNull(loader.getResource("demo/Application.java"));
+	}
+
+	@Test
+	public void resolveResourcesFromArchive() throws Exception {
+		LaunchedURLClassLoader loader = new LaunchedURLClassLoader(new URL[] { new URL(
+				"jar:file:src/test/resources/jars/app.jar!/") }, getClass()
+				.getClassLoader());
+		assertTrue(loader.getResources("demo/Application.java").hasMoreElements());
+	}
+
+	@Test
+	public void resolveRootPathFromArchive() throws Exception {
+		LaunchedURLClassLoader loader = new LaunchedURLClassLoader(new URL[] { new URL(
+				"jar:file:src/test/resources/jars/app.jar!/") }, getClass()
+				.getClassLoader());
+		assertNotNull(loader.getResource(""));
+	}
+
+	@Test
+	public void resolveRootResourcesFromArchive() throws Exception {
+		LaunchedURLClassLoader loader = new LaunchedURLClassLoader(new URL[] { new URL(
+				"jar:file:src/test/resources/jars/app.jar!/") }, getClass()
+				.getClassLoader());
+		assertTrue(loader.getResources("").hasMoreElements());
+	}
+
+}

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

@@ -126,7 +126,6 @@ public class ExplodedArchiveTests {
 	}
 
 	@Test
-	@SuppressWarnings("resource")
 	public void getFilteredArchive() throws Exception {
 		Archive filteredArchive = this.archive
 				.getFilteredArchive(new Archive.EntryRenameFilter() {