at.chrl.callbacks.enhancer.CallbackClassFileTransformer Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of chrl-callbacks Show documentation
Callback Framework to hook up on method calls with annotations
There is a newer version: 1.1.0
/**
 * This file is part of aion-lightning .
 * 
 * aion-lightning is free software: you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation, either version 3 of the License, or (at your option) any
 * later version.
 * 
 * aion-lightning is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
 * details.
 * 
 * You should have received a copy of the GNU General Public License along with
 * aion-lightning. If not, see .
 */
package at.chrl.callbacks.enhancer;

import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.security.ProtectionDomain;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import at.chrl.nutils.ExitCode;

/**
 * Basic class that checks if class can be transformed. JDK classes are not a
 * subject of transformation.
 *
 * @author SoulKeeper
 */
public abstract class CallbackClassFileTransformer implements ClassFileTransformer {

	private static final Logger log = LoggerFactory.getLogger(CallbackClassFileTransformer.class);

	/**
	 * This method analyzes class and adds callback support if needed.
	 *
	 * @param loader
	 *            ClassLoader of class
	 * @param className
	 *            class name
	 * @param classBeingRedefined
	 *            not used
	 * @param protectionDomain
	 *            not used
	 * @param classfileBuffer
	 *            basic class data
	 */
	@Override
	public byte[] transform(ClassLoader loader, String className, Class classBeingRedefined, ProtectionDomain protectionDomain, byte[] classfileBuffer) throws IllegalClassFormatException {
		try {
			// no need to scan whole jvm boot classpath
			// also there is no need to transform classes from jvm 'ext' dir
			if (loader == null || loader.getClass().getName().equals("sun.misc.Launcher$ExtClassLoader")) {
				log.trace("Class " + className + " ignored.");
				return null;
			}

			// actual class transformation
			return transformClass(loader, classfileBuffer);
		} catch (Exception e) {

			Error e1 = new Error("Can't transform class " + className, e);
			log.error(e1.getMessage(), e1);

			// if it is a class from core (not a script) - terminate server
			// noinspection ConstantConditions
			if (loader.getClass().getName().equals("sun.misc.Launcher$AppClassLoader")) {
				Runtime.getRuntime().halt(ExitCode.CODE_ERROR);
			}

			throw e1;
		}
	}

	/**
	 * Actually transforms the class.
	 *
	 * @param loader
	 *            class loader of this class
	 * @param clazzBytes
	 *            class bytes
	 * @return class as byte array if was transformed or null if was not
	 * @throws Exception
	 *             if something went wrong
	 */
	protected abstract byte[] transformClass(ClassLoader loader, byte[] clazzBytes) throws Exception;
}