代理模式

靜態(tài)代理

public interface Subject{
    void doSomething();
}

public class RealSubject implements Subject{
    @Override
    public void doSomething() {
        System.out.println( "call doSomething()" );
    }
}

public class AnotherRealSubject implements Subject{
    @Override
    public void doSomething() {
        System.out.println("call another doSomething().");
    }
}

public class TestProxy {
    public static void main(String[] args) {
        // static proxy
        new SubjectProxy().doSomething();
    }
}
// output:
// call doSomething()

動(dòng)態(tài)代理

// 動(dòng)態(tài)代理的核心，將代理類抽象出來，作為獨(dú)立邏輯
public class ProxyHandler implements InvocationHandler{

    private Object target;

    /**
     *  綁定委托對(duì)象，并返回代理類
     */
    public Object bind(Object target){
        this.target = target;
        //綁定該類實(shí)現(xiàn)的所有接口，取得代理類
        return Proxy.newProxyInstance(target.getClass().getClassLoader(), target.getClass().getInterfaces(), this);
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        Object result = null;
        //這里就可以進(jìn)行所謂的AOP編程了
        //在調(diào)用具體函數(shù)方法前，執(zhí)行功能處理
        result= method.invoke(target, args);
        //在調(diào)用具體函數(shù)方法后，執(zhí)行功能處理

        return result;
    }
}

public class TestProxy {
    public static void main(String[] args) {
        // dynamical proxy
        ProxyHandler proxyHandler = new ProxyHandler();
        // Object 1
        Subject subject = (Subject) proxyHandler.bind(new RealSubject());
        subject.doSomething();
        // Object 2
        Subject mocked = (Subject) proxyHandler.bind(new AnotherRealSubject());
        mocked.doSomething();
    }
}

// output:
// call doSomething()
// call doSomething()
// call another doSomething().

由上圖代碼可看到，proxy邏輯被抽象到ProxyHandler中，與業(yè)務(wù)完全解耦，業(yè)務(wù)中只需要?jiǎng)討B(tài)綁定委托對(duì)象，即可對(duì)委托對(duì)象的中的方法增強(qiáng)處理。