ParentLastClassLoader.java

package org.hotswap.agent.plugin.proxy;

import java.io.IOException;
import java.io.InputStream;

/**
 * 
 * Tries to load classes by itself first. Tries the parent Classloader last.
 * 
 * @author Erki Ehtla
 * 
 */
public class ParentLastClassLoader extends ClassLoader {
	public static final String[] EXCLUDED_PACKAGES = new String[] { "java.", "javax.", "sun.", "oracle." };
	
	public ParentLastClassLoader(ClassLoader parent) {
		super(parent);
	}
	
	@Override
	protected Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException {
		for (String excludedPackage : EXCLUDED_PACKAGES) {
			if (name.startsWith(excludedPackage))
				return super.loadClass(name, resolve);
		}
		Class<?> clazz = loadClassFromThisClassLoader(name);
		if (clazz == null)
			return super.loadClass(name, resolve);
		
		if (resolve) {
			resolveClass(clazz);
		}
		return clazz;
	}
	
	protected Class<?> loadClassFromThisClassLoader(String name) throws ClassNotFoundException {
		Class<?> result = findLoadedClass(name);
		if (result != null) {
			return result;
		}
		byte[] bytes = readClass(name);
		if (bytes != null) {
			return defineClass(name, bytes, 0, bytes.length);
		}
		return null;
	}
	
	protected byte[] readClass(String name) throws ClassNotFoundException {
		InputStream is = getParent().getResourceAsStream(name.replace('.', '/') + ".class");
		if (is == null) {
			return null;
		}
		try {
			return ProxyTransformationUtils.copyToByteArray(is);
		} catch (IOException ex) {
			throw new ClassNotFoundException("Could not read: " + name, ex);
		}
	}
}