java 代理和动态代理

第三种关系成为代理，举一个例子，你需要去某公司问问这个公司的相关业务，那么前台的漂亮妹妹就可以充当这个代理，她帮你询问然后告诉你。

扯点正经的吧。。。。

例如，太空船需要一个控制模块：

//: reusing/SpaceShipControls.java package reusing; /* Added by Eclipse.py */ public class SpaceShipControls { void up(int velocity) {} void down(int velocity) {} void left(int velocity) {} void right(int velocity) {} void forward(int velocity) {} void back(int velocity) {} void turboBoost() {} } ///:~ 以下是代理方法：

//: reusing/SpaceShipDelegation.java package reusing; /* Added by Eclipse.py */ public class SpaceShipDelegation { private String name; private SpaceShipControls controls = new SpaceShipControls(); public SpaceShipDelegation(String name) { this.name = name; } // Delegated methods: public void back(int velocity) { controls.back(velocity); } public void down(int velocity) { controls.down(velocity); } public void forward(int velocity) { controls.forward(velocity); } public void left(int velocity) { controls.left(velocity); } public void right(int velocity) { controls.right(velocity); } public void turboBoost() { controls.turboBoost(); } public void up(int velocity) { controls.up(velocity); } public static void main(String[] args) { SpaceShipDelegation protector = new SpaceShipDelegation("NSEA Protector"); protector.forward(100); } } ///:~ 代理的好处是不暴露你访问的对象，具有安全性。

好了，下面就说动态代理了

通过调用静态方法 Proxy.newProxyInstance()可以创建动态代理，这个方法需要三个参数

1.一个类加载器

2.一个你希望该代理实现的接口列表

3.  InvocationHandler 的实现

还有一个 invoke() 方法，该方法传递进来了代理对象，通常你会执行被代理的对象，通过Method,invoke() 将请求转发给被代理对象，并传入其他的参数。

以下是实际的例子

//: typeinfo/SelectingMethods.java // Looking for particular methods in a dynamic proxy. import java.lang.reflect.*; class MethodSelector implements InvocationHandler { private Object proxied; public MethodSelector(Object proxied) { this.proxied = proxied; } public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { if(method.getName().equals("interesting")) System.out.println("Proxy detected the interesting method"); return method.invoke(proxied, args); } } interface SomeMethods { void boring1(); void boring2(); void interesting(String arg); void boring3(); } class Implementation implements SomeMethods { public void boring1() { System.out.println("boring1"); } public void boring2() { System.out.println("boring2"); } public void interesting(String arg) { System.out.println("interesting " + arg); } public void boring3() { System.out.println("boring3"); } } class SelectingMethods { public static void main(String[] args) { SomeMethods proxy= (SomeMethods)Proxy.newProxyInstance( SomeMethods.class.getClassLoader(), new Class[]{ SomeMethods.class }, new MethodSelector(new Implementation())); proxy.boring1(); proxy.boring2(); proxy.interesting("bonobo"); proxy.boring3(); } } /* Output: boring1 boring2 Proxy detected the interesting method interesting bonobo boring3 *///:~