/*
* Copyright 2015 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 com.github.atdi.gboot.loader;
import com.github.atdi.gboot.loader.jar.GBootJarFile;
import com.github.atdi.gboot.loader.jar.Handler;
import java.net.URL;
import java.net.URLClassLoader;
import java.io.IOException;
import java.security.AccessController;
import java.security.PrivilegedExceptionAction;
import java.util.Arrays;
import java.util.Collections;
import java.util.Enumeration;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* Custom class loader, which loads the
* jars from lib folder.
*/
@SuppressWarnings("PMD.EmptyCatchBlock")
public class GBootClassLoader extends URLClassLoader {
private static LockProvider LOCK_PROVIDER = setupLockProvider();
private final ClassLoader rootClassLoader;
private static final Logger logger = Logger.getLogger(GBootClassLoader.class.getName());
/**
* Create a new {@link GBootClassLoader} instance.
* @param urls the URLs from which to load classes and resources
* @param parent the parent class loader for delegation
*/
public GBootClassLoader(URL[] urls, ClassLoader parent) {
super(urls, parent);
this.rootClassLoader = findRootClassLoader(parent);
}
private ClassLoader findRootClassLoader(ClassLoader classLoader) {
while (classLoader != null) {
if (classLoader.getParent() == null) {
return classLoader;
}
classLoader = classLoader.getParent();
}
return null;
}
@Override
public URL getResource(String name) {
URL url = null;
if (this.rootClassLoader != null) {
url = this.rootClassLoader.getResource(name);
}
return (url == null ? findResource(name) : url);
}
@Override
public URL findResource(String name) {
try {
if (name.equals("") && hasURLs()) {
return getURLs()[0];
}
return super.findResource(name);
}
catch (IllegalArgumentException ex) {
return null;
}
}
@Override
public Enumeration<URL> findResources(String name) throws IOException {
if (name.equals("") && hasURLs()) {
return Collections.enumeration(Arrays.asList(getURLs()));
}
return super.findResources(name);
}
private boolean hasURLs() {
return getURLs().length > 0;
}
@Override
public Enumeration<URL> getResources(String name) throws IOException {
if (this.rootClassLoader == null) {
return findResources(name);
}
final Enumeration<URL> rootResources = this.rootClassLoader.getResources(name);
final Enumeration<URL> localResources = findResources(name);
return new Enumeration<URL>() {
@Override
public boolean hasMoreElements() {
return rootResources.hasMoreElements()
|| localResources.hasMoreElements();
}
@Override
public URL nextElement() {
if (rootResources.hasMoreElements()) {
return rootResources.nextElement();
}
return localResources.nextElement();
}
};
}
/**
* Attempt to load classes from the URLs before delegating to the parent loader.
*/
@Override
protected Class<?> loadClass(String name, boolean resolve)
throws ClassNotFoundException {
synchronized (GBootClassLoader.LOCK_PROVIDER.getLock(this, name)) {
Class<?> loadedClass = findLoadedClass(name);
if (loadedClass == null) {
Handler.setUseFastConnectionExceptions(true);
try {
loadedClass = doLoadClass(name);
}
finally {
Handler.setUseFastConnectionExceptions(false);
}
}
if (resolve) {
resolveClass(loadedClass);
}
return loadedClass;
}
}
private Class<?> doLoadClass(String name) throws ClassNotFoundException {
// 1) Try the root class loader
try {
if (this.rootClassLoader != null) {
return this.rootClassLoader.loadClass(name);
}
}
catch (ClassNotFoundException ex) {
// Do nothing for performance issues
}
// 2) Try to find locally
try {
findPackage(name);
Class<?> cls = findClass(name);
return cls;
}
catch (ClassNotFoundException ex) {
// Do nothing for performance issues
}
// 3) Use standard loading
return super.loadClass(name, false);
}
private void findPackage(final String name) throws ClassNotFoundException {
int lastDot = name.lastIndexOf('.');
if (lastDot != -1) {
String packageName = name.substring(0, lastDot);
if (getPackage(packageName) == null) {
try {
definePackageForFindClass(name, packageName);
}
catch (Exception ex) {
// Do nothing for performance issues
}
}
}
}
/**
* Define a package before a {@code findClass} call is made. This is necessary to
* ensure that the appropriate manifest for nested JARs associated with the package.
* @param name the class name being found
* @param packageName the package
*/
private void definePackageForFindClass(final String name, final String packageName) {
try {
AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {
@Override
public Object run() throws ClassNotFoundException {
String path = name.replace('.', '/').concat(".class");
for (URL url : getURLs()) {
try {
if (url.getContent() instanceof GBootJarFile) {
GBootJarFile jarFile = (GBootJarFile) url.getContent();
// Check the jar entry data before needlessly creating the
// manifest
if (jarFile.getJarEntryData(path) != null
&& jarFile.getManifest() != null) {
definePackage(packageName, jarFile.getManifest(), url);
return null;
}
}
}
catch (IOException ex) {
logger.log(Level.WARNING, String.format("Failed to define package %s for class %s",
packageName, name), ex);
}
}
return null;
}
}, AccessController.getContext());
}
catch (java.security.PrivilegedActionException ex) {
logger.log(Level.SEVERE, String.format("Security error for package %s and class and %s",
packageName, name), ex);
}
}
private static LockProvider setupLockProvider() {
try {
ClassLoader.registerAsParallelCapable();
return new Java7LockProvider();
}
catch (NoSuchMethodError ex) {
return new LockProvider();
}
}
/**
* Strategy used to provide the synchronize lock object to use when loading classes.
*/
private static class LockProvider {
public Object getLock(GBootClassLoader classLoader, String className) {
return classLoader;
}
}
/**
* Java 7 specific {@link GBootClassLoader.LockProvider}.
*/
private static class Java7LockProvider extends LockProvider {
@Override
public Object getLock(GBootClassLoader classLoader, String className) {
return classLoader.getClassLoadingLock(className);
}
}
}