java agent

package com.test;

import java.io.*;
import java.lang.instrument.*;
import java.security.*;

public class dumper
{
    //A java agent must have a premain method which acts as the entry-point
    public static void premain(String agentArgs, Instrumentation inst)
    {
        System.out.println("agent loaded");

        // Register our transformer
        inst.addTransformer(new transformer());
    }
}

class transformer implements ClassFileTransformer
{
    String destFolder = "d:/test/";
    // The transform method is called for each non-system class as they are being loaded
    public byte[] transform(ClassLoader loader, String className,
                            Class<?> classBeingRedefined, ProtectionDomain protectionDomain,
                            byte[] classfileBuffer) throws IllegalClassFormatException
    {
        if (className != null)
        {
            // Skip all system classes
//            if (!className.startsWith("java") &&
//                    !className.startsWith("sun") &&
//                    !className.startsWith("javax") &&
//                    !className.startsWith ("com") &&
//                    !className.startsWith("jdk") &&
//                    !className.startsWith("org"))
//            {
            if(className.startsWith ("com/fr"))
            {
                System.out.println("Dumping: " + className);

                // Replace all separator charactors
                //String newName = className.replaceAll("/", "#") + ".class";
                String newName = destFolder + className.replace(".", "/") + ".class";

                File destFile = new File(newName);
                File destDirectory = destFile.getParentFile();
                destDirectory.mkdirs();

                try
                {
                    FileOutputStream fos = new FileOutputStream(newName);
                    fos.write(classfileBuffer);
                    fos.close();
                }
                catch (Exception ex)
                {
                    System.out.println("Exception while writing: " + newName);
                }
            }
        }
        // We are not modifying the bytecode in anyway, so return it as-is
        return classfileBuffer;
    }
}

MANIFEST.MF

Manifest-Version: 1.0
Premain-Class: com.test.dumper

@echo 此Bat将启动大内存版本的设计器
..\jre\bin\java -javaagent:jagent.jar -Xms512m -Xmx1024m -cp ../lib/*;../lib/jetty/*;../WebReport/WEB-INF/lib/* com.fr.start.Designer demo