Dynamic Proxy

对于Dynamic Proxy的原理，很多地方都有介绍，里面最神秘的就是JVM会在运行时动态生成一个类，好奇心驱使，想看看这个生成的类的代码是啥样的。于是，跟踪到Proxy.newProxyInstance()中，发现生成代码的关键语句byte[] ProxyGenerator.generateProxyClass(String proxyname,Class[] instances)，写了段代码来输出那个类文件，并得到反编译的结果
----------IPerson .java-----------
package cn.edu.tju.bme;

public interface IPerson {

public void insertPerson();
public String getPersonName();
}
----------TestInvocationHandler.java-----------
package cn.edu.tju.bme;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;

public class TestInvocationHandler implements InvocationHandler {

public Object invoke(Object proxy, Method method, Object[] args)
throws Throwable {
// TODO Auto-generated method stub
return null;
}
}
------------Main.java-----------
package cn.edu;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.lang.reflect.InvocationHandler;

import sun.misc.ProxyGenerator;

import cn.edu.tju.bme.IPerson;
import cn.edu.tju.bme.TestInvocationHandler;

public class Main {
public static void main(String[] args) throws IOException {
String proxyName = "proxyName";
InvocationHandler handler = new TestInvocationHandler();
byte[] proxyClassFile = ProxyGenerator.generateProxyClass( proxyName, new Class[]{IPerson.class});
FileOutputStream fos = new FileOutputStream(new File("D:\\ProxyName.class"));
fos.write(proxyClassFile);
fos.flush();
fos.close();
}
}
---------------------------
反编译生成的ProxyName.class，得到的源文件如下：
----------proxyName.java-----------
import cn.edu.tju.bme.IPerson;
import java.lang.reflect.*;

public final class proxyName extends Proxy
implements IPerson
{

public proxyName(InvocationHandler invocationhandler)
{
super(invocationhandler);
}

public final String toString()
{
try
{
return (String)super.h.invoke(this, m2, null);
}
catch(Error _ex) { }
catch(Throwable throwable)
{
throw new UndeclaredThrowableException(throwable);
}
}

public final int hashCode()
{
try
{
return ((Integer)super.h.invoke(this, m0, null)).intValue();
}
catch(Error _ex) { }
catch(Throwable throwable)
{
throw new UndeclaredThrowableException(throwable);
}
}

public final String getPersonName ()
{
try
{
return (String)super.h.invoke(this, m4, null);
}
catch(Error _ex) { }
catch(Throwable throwable)
{
throw new UndeclaredThrowableException(throwable);
}
}

public final void insertPerson ()
{
try
{
super.h.invoke(this, m3, null);
return;
}
catch(Error _ex) { }
catch(Throwable throwable)
{
throw new UndeclaredThrowableException(throwable);
}
}

public final boolean equals(Object obj)
{
try
{
return ((Boolean)super.h.invoke(this, m1, new Object[] {
obj
})).booleanValue();
}
catch(Error _ex) { }
catch(Throwable throwable)
{
throw new UndeclaredThrowableException(throwable);
}
}

private static Method m2;
private static Method m0;
private static Method m4;
private static Method m3;
private static Method m1;

static
{
try
{
m2 = Class.forName("java.lang.Object").getMethod("toString", new Class[0]);
m0 = Class.forName("java.lang.Object").getMethod("hashCode", new Class[0]);
m4 = Class.forName("cn.edu.tju.bme.IPerson").getMethod("getPersonName", new Class[0]);
m3 = Class.forName("cn.edu.tju.bme.IPerson").getMethod("insertPerson", new Class[0]);
m1 = Class.forName("java.lang.Object").getMethod("equals", new Class[] {
Class.forName("java.lang.Object")
});
}
catch(NoSuchMethodException nosuchmethodexception)
{
throw new NoSuchMethodError(nosuchmethodexception.getMessage());
}