org.apache.ibatis.io.ClassLoaderWrapper Maven / Gradle / Ivy
/**
* Copyright 2009-2015 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 org.apache.ibatis.io;
import java.io.InputStream;
import java.net.URL;
/**
* A class to wrap access to multiple class loaders making them work as one
*
* @author Clinton Begin
*/
public class ClassLoaderWrapper {
ClassLoader defaultClassLoader;
ClassLoader systemClassLoader;
ClassLoaderWrapper() {
try {
systemClassLoader = ClassLoader.getSystemClassLoader();
} catch (SecurityException ignored) {
// AccessControlException on Google App Engine
}
}
/*
* Get a resource as a URL using the current class path
*
* @param resource - the resource to locate
* @return the resource or null
*/
public URL getResourceAsURL(String resource) {
return getResourceAsURL(resource, getClassLoaders(null));
}
/*
* Get a resource from the classpath, starting with a specific class loader
*
* @param resource - the resource to find
* @param classLoader - the first classloader to try
* @return the stream or null
*/
public URL getResourceAsURL(String resource, ClassLoader classLoader) {
return getResourceAsURL(resource, getClassLoaders(classLoader));
}
/*
* Get a resource from the classpath
*
* @param resource - the resource to find
* @return the stream or null
*/
public InputStream getResourceAsStream(String resource) {
return getResourceAsStream(resource, getClassLoaders(null));
}
/*
* Get a resource from the classpath, starting with a specific class loader
*
* @param resource - the resource to find
* @param classLoader - the first class loader to try
* @return the stream or null
*/
public InputStream getResourceAsStream(String resource, ClassLoader classLoader) {
return getResourceAsStream(resource, getClassLoaders(classLoader));
}
/*
* Find a class on the classpath (or die trying)
*
* @param name - the class to look for
* @return - the class
* @throws ClassNotFoundException Duh.
*/
public Class classForName(String name) throws ClassNotFoundException {
return classForName(name, getClassLoaders(null));
}
/*
* Find a class on the classpath, starting with a specific classloader (or die trying)
*
* @param name - the class to look for
* @param classLoader - the first classloader to try
* @return - the class
* @throws ClassNotFoundException Duh.
*/
public Class classForName(String name, ClassLoader classLoader) throws ClassNotFoundException {
return classForName(name, getClassLoaders(classLoader));
}
/*
* Try to get a resource from a group of classloaders
*
* @param resource - the resource to get
* @param classLoader - the classloaders to examine
* @return the resource or null
*/
InputStream getResourceAsStream(String resource, ClassLoader[] classLoader) {
for (ClassLoader cl : classLoader) {
if (null != cl) {
// try to find the resource as passed
InputStream returnValue = cl.getResourceAsStream(resource);
// now, some class loaders want this leading "/", so we'll add it and try again if we didn't find the resource
if (null == returnValue) {
returnValue = cl.getResourceAsStream("/" + resource);
}
if (null != returnValue) {
return returnValue;
}
}
}
return null;
}
/*
* Get a resource as a URL using the current class path
*
* @param resource - the resource to locate
* @param classLoader - the class loaders to examine
* @return the resource or null
*/
URL getResourceAsURL(String resource, ClassLoader[] classLoader) {
URL url;
for (ClassLoader cl : classLoader) {
if (null != cl) {
// look for the resource as passed in...
url = cl.getResource(resource);
// ...but some class loaders want this leading "/", so we'll add it
// and try again if we didn't find the resource
if (null == url) {
url = cl.getResource("/" + resource);
}
// "It's always in the last place I look for it!"
// ... because only an idiot would keep looking for it after finding it, so stop looking already.
if (null != url) {
return url;
}
}
}
// didn't find it anywhere.
return null;
}
/*
* Attempt to load a class from a group of classloaders
*
* @param name - the class to load
* @param classLoader - the group of classloaders to examine
* @return the class
* @throws ClassNotFoundException - Remember the wisdom of Judge Smails: Well, the world needs ditch diggers, too.
*/
Class classForName(String name, ClassLoader[] classLoader) throws ClassNotFoundException {
for (ClassLoader cl : classLoader) {
if (null != cl) {
try {
Class c = Class.forName(name, true, cl);
if (null != c) {
return c;
}
} catch (ClassNotFoundException e) {
// we'll ignore this until all classloaders fail to locate the class
}
}
}
throw new ClassNotFoundException("Cannot find class: " + name);
}
ClassLoader[] getClassLoaders(ClassLoader classLoader) {
return new ClassLoader[]{
classLoader,
defaultClassLoader,
Thread.currentThread().getContextClassLoader(),
getClass().getClassLoader(),
systemClassLoader};
}
}