JVM技术 反射与动态代理

源：http://www.educity.cn/it/sun/200901111502051421.htm
评：
动态代理

    Sun对动态代理的说明：

    一个简单例子代码：

    动态代理的内部实现——代码生成：

    研究JDK源代码，发现在Proxy的sun实现中调用了sun.misc.ProxyGenerator类的generateProxyClass( proxyName, interfaces)方法，其返回值为byte[]和class文件的内存类型一致。于是做如下试验：

    public class  ProxyClassFile{
    public static void main(String[] args){
    String proxyName = "TempProxy";
    TempImpl t = new TempImpl("proxy");
    Class[] interfaces =t.getClass().getInterfaces();
    byte[] proxyClassFile = ProxyGenerator.generateProxyClass(
    proxyName, interfaces);
    File f = new File("classes/TempProxy.class");
    try {
    FileOutputStream fos = new FileOutputStream(f);
    fos.write(proxyClassFile);
    fos.flush();
    fos.close();
    } catch (FileNotFoundException e) {
    e.printStackTrace();  //To change body of catch statement use File | Settings | File Templates.
    } catch (IOException e) {
    e.printStackTrace();  //To change body of catch statement use File | Settings | File Templates.
    }
    }
    }

运行该类，到class文件夹下，利用反编译技术，发现原来其采用了代码生产技术：

    public interface Temp{
    public void Talk();
    public void Run();
    }
    import java.lang.reflect.*;
    public final class TempProxy extends Proxy
    implements Temp{
    private static Method m4;
    private static Method m2;
    private static Method m0;
    private static Method m3;
    private static Method m1;
    public TempProxy(InvocationHandler invocationhandler)   {
    super(invocationhandler);
    }
    public final void Run()    {
    try {
    h.invoke(this, m4, null);
    return;
    }
    catch(Error _ex) { }
    catch(Throwable throwable)  {
    throw new UndeclaredThrowableException(throwable);
    }
    }
    public final String toString(){
    try{
    return (String)h.invoke(this, m2, null);
    }
    catch(Error _ex) { }
    catch(Throwable throwable)  {
    throw new UndeclaredThrowableException(throwable);
    }
    return "";
    }
    public final int hashCode() {
    try {
    return ((Integer)h.invoke(this, m0, null)).intValue();
    }
    catch(Error _ex) { }
    catch(Throwable throwable){
    throw new UndeclaredThrowableException(throwable);
    }
    return 123;
    }
    public final void Talk(){
    try{
    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)h.invoke(this, m1, new Object[] {
    obj
    })).booleanValue();
    }
    catch(Error _ex) { }
    catch(Throwable throwable) {
    throw new UndeclaredThrowableException(throwable);
    }
    return false;
    }
    static{
    try{
    m4 = Class.forName("Temp").getMethod("Run", new Class[0]);
    m2 = Class.forName("java.lang.Object").getMethod("toString", new Class[0]);
    m0 = Class.forName("java.lang.Object").getMethod("hashCode", new Class[0]);
    m3 = Class.forName("Temp").getMethod("Talk", 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());
    }
    catch(ClassNotFoundException classnotfoundexception) {
    throw new NoClassDefFoundError(classnotfoundexception.getMessage());
    }
    }
    }