/*
* Copyright (c) 2007 BUSINESS OBJECTS SOFTWARE LIMITED
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* * Neither the name of Business Objects nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/*
* ClassInfo.java
* Creation date: Jan 4, 2006.
* By: Edward Lam
*/
package org.openquark.util;
import java.io.IOException;
import java.net.URL;
import java.util.Collections;
import java.util.Enumeration;
import java.util.LinkedHashSet;
import java.util.Set;
/**
* A helper class to return class-related information based on the current execution environment.
* @author Edward Lam
*/
public final class ClassInfo {
/** Singleton finder instance. */
private static final CallingClassFinder FINDER = new CallingClassFinder();
/**
* A class to determine the class of a method in the current execution stack.
* @author Edward Lam
*/
private static class CallingClassFinder extends SecurityManager {
/**
* {@inheritDoc}
* Calls superclass but exposes as public visibility.
*/
@Override
public Class<?>[] getClassContext() {
return super.getClassContext();
}
/**
* Get a class in the currently executing call chain.
* @param callDepth the call depth.
* @return the class callDepth-levels higher in the currently-executing call chain.
* 0 == the class of the method calling this method.
* 1 == the class of the method one level higher.
*/
public Class<?> getCallingClass(int callDepth) {
Class<?> stack[] = getClassContext();
// stack[0] == class for method getCallingClass(callDepth) ie. CallingClassFinder.
// stack[1] == class of method calling this method
// ...
return stack[callDepth + 1];
}
}
/**
* Constructor for a ClassInfo.
* Not intended to be instantiated.
*/
private ClassInfo() {
}
/**
* Get a class in the currently executing call chain.
* @param callDepth the call depth.
* @return the class callDepth-levels higher in the currently-executing call chain.
* 0 == the class of the method calling this method.
* 1 == the class of the method one level higher.
*/
public static Class<?> getCallingClass(int callDepth) {
// pass in 0: this method's class.
// pass in 1: the caller's class.
return FINDER.getCallingClass(callDepth + 1);
}
/**
* @return the classes in the currently executing call chain.
* Note that this will include the ClassInfo class itself.
*/
public static Class<?>[] getClassContext() {
return FINDER.getClassContext();
}
/**
* Load a class.
* If there is a context classloader, this is first used to attempt to load the class.
* If this fails then the caller's classloader is used.
*
* @param name the fully-qualified name of the class.
* @return the corresponding class.
* @throws ClassNotFoundException if the class could not be found.
*/
public static Class<?> loadClass(String name) throws ClassNotFoundException {
// Note about implementation: this is how antlr.Utils.loadClass() does it,
// except that it calls the one-arg Class.forName().
try {
ClassLoader contextClassLoader = Thread.currentThread().getContextClassLoader();
if (contextClassLoader != null) {
return contextClassLoader.loadClass(name);
}
// fall through
} catch (Exception e) {
// fall through
}
return Class.forName(name, true, getCallingClass(1).getClassLoader());
}
/**
* Get a resource by name.
* If there is a context classloader, this is first used to attempt to load the resource.
* If this fails then the classloader of the calling class will be used.
*
* @param name the name of the resource
* @return the URL to that resource, or null if that resource could not be found.
*/
public static URL getResource(final String name) {
try {
ClassLoader contextClassLoader = Thread.currentThread().getContextClassLoader();
if (contextClassLoader != null) {
URL resource = contextClassLoader.getResource(name);
if (resource != null) {
return resource;
}
}
// fall through
} catch (Exception e) {
// fall through
}
return getCallingClass(1).getClassLoader().getResource(name);
}
/**
* Get all resources with a given name.
* The returned enumeration will have all resources available to both the caller's classloader and the context classloader (if any).
*
* @param name the name of the resource.
* @return the URLs for the found resources.
* @throws IOException
*/
public static Enumeration<URL> getResources(final String name) throws IOException {
// Use a set to avoid duplicates.
// Might as well make it an ordered set to make things potentially easier for clients.
Set<URL> resourceSet = new LinkedHashSet<URL>();
try {
ClassLoader contextClassLoader = Thread.currentThread().getContextClassLoader();
if (contextClassLoader != null) {
resourceSet.addAll(Collections.list(contextClassLoader.getResources(name)));
}
// fall through
} catch (Exception e) {
// fall through
}
resourceSet.addAll(Collections.list(getCallingClass(1).getClassLoader().getResources(name)));
return Collections.enumeration(resourceSet);
}
}