动态代理实现

   由于种种原因,最近在对以前用过的技术进行回顾梳理，在这期间发现hibernate与spring在很大程度上用到动态代理，象hibernate里面的延迟加载，加载的是代理的id,当get()非id的时候，才会实例具体的对象。spring的核心之一aop,也是通过动态代理实现的。下面先看一个简单的动态代理demo。

被代理类：

public class MyClass {
	public void method() {
		System.out.println("MyClass.method()");
	}
}

代理类：

import java.lang.reflect.Method;
 
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodProxy;
import net.sf.cglib.proxy.MethodInterceptor;
 
public class Main {
	public static void main(String[] args) {
		Enhancer enhancer = new Enhancer();
		enhancer.setSuperclass(MyClass.class);
		enhancer.setCallback( new MethodInterceptorImpl() );
		MyClass my = (MyClass)enhancer.create();
		my.method();
	}
 
	private static class MethodInterceptorImpl implements MethodInterceptor {
		public Object intercept(Object obj, 
                                Method method, 
                                Object[] args, 
                                MethodProxy proxy) throws Throwable {
			System.out.println(method);
			proxy.invokeSuper(obj, args);
			return null;
		}
	}
}

  类似Enhancer可以增加CallbackFilter

  另外一种实现与spring类相似：

public interface MyInterfaceA {
	public void methodA();
}

public interface  MyInterfaceB {
	public void methodB();
}

public class MyInterfaceAImpl implements MyInterfaceA {
 
	public void methodA() {
		System.out.println("MyInterfaceAImpl.methodA()");
	}
}

public class MyInterfaceBImpl implements MyInterfaceB {
 
	public void methodB() {
		System.out.println("MyInterfaceBImpl.methodB()");
	}
}

import net.sf.cglib.proxy.Mixin;
 
public class Main {
 
	public static void main(String[] args) {
 
		Class[] interfaces =
			new Class[] { MyInterfaceA.class, MyInterfaceB.class };
		
		Object[] delegates =
			new Object[] { new MyInterfaceAImpl(), new MyInterfaceBImpl() };
			
		
		Object obj = Mixin.create(interfaces, delegates);
 
 
		MyInterfaceA myA = (MyInterfaceA)obj;
		myA.methodA();
 
 
		MyInterfaceB myB = (MyInterfaceB)obj;
		myB.methodB();
	}
}