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/* * This java source file is placed into the public domain. * * The orginal author is Ceki Gulcu, QOS.ch * * THIS SOFTWARE IS PROVIDED AS-IS WITHOUT WARRANTY OF ANY KIND, NOT EVEN * THE IMPLIED WARRANTY OF MERCHANTABILITY. THE AUTHOR OF THIS SOFTWARE, * ASSUMES _NO_ RESPONSIBILITY FOR ANY CONSEQUENCE RESULTING FROM THE * USE, MODIFICATION, OR REDISTRIBUTION OF THIS SOFTWARE. */ package ch.qos; import java.net.URL; import java.net.URLClassLoader; /** * An almost trivial no-fuss implementation of a class loader * following the child-first delegation model. * * @author Ceki Gulcu */ public class ChildFirstClassLoader extends URLClassLoader { public ChildFirstClassLoader(URL[] urls) { super(urls); } public ChildFirstClassLoader(URL[] urls, ClassLoader parent) { super(urls, parent); } public void addURL(URL url) { super.addURL(url); } public Class loadClass(String name) throws ClassNotFoundException { return loadClass(name, false); } /** * We override the parent-first behavior established by * java.lang.Classloader. *

* The implementation is surprisingly straightforward. */ protected Class loadClass(String name, boolean resolve) throws ClassNotFoundException { //System.out.println("ChildFirstClassLoader("+name+", "+resolve+")"); // First, check if the class has already been loaded Class c = findLoadedClass(name); // if not loaded, search the local (child) resources if (c == null) { try { c = findClass(name); } catch(ClassNotFoundException cnfe) { // ignore } } // if we could not find it, delegate to parent // Note that we don't attempt to catch any ClassNotFoundException if (c == null) { if (getParent() != null) { c = getParent().loadClass(name); } else { c = getSystemClassLoader().loadClass(name); } } if (resolve) { resolveClass(c); } return c; } /** * Override the parent-first resource loading model established by * java.lang.Classloader with child-first behavior. */ public URL getResource(String name) { URL url = findResource(name); // if local search failed, delegate to parent if(url == null) { url = getParent().getResource(name); } return url; } }