GeneratorParametersRecorder.java

package org.hotswap.agent.plugin.proxy.hscglib;

import java.io.ByteArrayInputStream;
import java.io.DataInputStream;
import java.util.concurrent.ConcurrentHashMap;

import org.hotswap.agent.logging.AgentLogger;

/**
 * Stores a GeneratorStrategy instance along with the parameter used to generate with it
 * 
 * @author Erki Ehtla
 * 
 */
public class GeneratorParametersRecorder {
	// this Map is used in the App ClassLoader
	public static ConcurrentHashMap<String, GeneratorParams> generatorParams = new ConcurrentHashMap<>();
	private static AgentLogger LOGGER = AgentLogger.getLogger(GeneratorParametersRecorder.class);
	
	/**
	 * 
	 * @param generatorStrategy
	 *            Cglib generator strategy instance that generated the bytecode
	 * @param classGenerator
	 *            parameter used to generate the bytecode with generatorStrategy
	 * @param bytes
	 *            generated bytecode
	 */
	public static void register(Object generatorStrategy, Object classGenerator, byte[] bytes) {
		try {
			generatorParams.putIfAbsent(getClassName(bytes), new GeneratorParams(generatorStrategy, classGenerator));
		} catch (Exception e) {
			LOGGER.error("Error saving parameters of a creation of a Cglib proxy", e);
		}
	}
	
	/**
	 * http://stackoverflow.com/questions/1649674/resolve-class-name-from-bytecode
	 * 
	 * @param bytes
	 * @return
	 * @throws Exception
	 */
	public static String getClassName(byte[] bytes) throws Exception {
		DataInputStream dis = new DataInputStream(new ByteArrayInputStream(bytes));
		dis.readLong(); // skip header and class version
		int cpcnt = (dis.readShort() & 0xffff) - 1;
		int[] classes = new int[cpcnt];
		String[] strings = new String[cpcnt];
		for (int i = 0; i < cpcnt; i++) {
			int t = dis.read();
			if (t == 7)
				classes[i] = dis.readShort() & 0xffff;
			else if (t == 1)
				strings[i] = dis.readUTF();
			else if (t == 5 || t == 6) {
				dis.readLong();
				i++;
			} else if (t == 8)
				dis.readShort();
			else
				dis.readInt();
		}
		dis.readShort(); // skip access flags
		return strings[classes[(dis.readShort() & 0xffff) - 1] - 1].replace('/', '.');
	}
}