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代理簡記

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Java靜態(tài)代理 委托類和代理類肩刃，實現(xiàn)共同接口

共同接口：

public interface HelloService {
    void sayHello();
}

委托類：

public class Hello implements HelloService{

    @Override
    public void sayHello() {
        System.out.println("hi, this is Hello-Original.");
    }
}

代理類：

public class HelloProxy implements HelloService {

    private Hello source = new Hello();

    @Override
    public void sayHello() {
        before();
        source.sayHello();
        after();
    }

    private void before(){
        System.out.println("Before hello, I need prepare something...");
    }

    private void after(){
        System.out.println("After hello, I need conclude something...");
    }
}

測試結(jié)果：

public static void main(String[] args) {
        HelloProxy helloProxy = new HelloProxy();
        helloProxy.sayHello();
    }

Before hello, I need prepare something...
hi, this is Hello-Original.
After hello, I need conclude something...

Java動態(tài)代理 通過反射生成代理類
實現(xiàn) InvocationHandler 通過 Proxy.newProxyInstance 構(gòu)建

public class JavaProxyInvocationHandler implements InvocationHandler {

    private Object obj;

    public JavaProxyInvocationHandler(Object obj){
        this.obj = obj;
    }

    public Object newProxyInstance(){
        return Proxy.newProxyInstance(obj.getClass().getClassLoader(), obj.getClass().getInterfaces(), this);
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("obj invoked before...");
        Object result = method.invoke(obj, args);
        System.out.println("obj invoked after...");
        return result;
    }
}

測試結(jié)果：

public static void main(String[] args) {
        JavaProxyInvocationHandler proxyHandler = new JavaProxyInvocationHandler(new Hello());
        HelloService helloService = (HelloService) proxyHandler.newProxyInstance();
        helloService.sayHello();
    }

obj invoked before...
hi, this is Hello-Original.
obj invoked after...

CGLib 動態(tài)代理 底層將方法全部存入一個數(shù)組中，通過數(shù)組索引直接進行方法調(diào)用
方法調(diào)用：通過字節(jié)碼文件生成委托類的子類，對非 final 委托方法生成兩個方法：委托方法簽名相同的方法，它在方法中會通過super調(diào)用委托方法片迅；代理類獨有的方法腮鞍，它會判斷是否存在實現(xiàn)了MethodInterceptor接口的對象，若存在則將調(diào)用intercept方法對委托方法進行代理害驹。

public class HelloMethodInterceptor implements MethodInterceptor {
    @Override
    public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
        System.out.println("HelloMethodInterceptor: before...");
        Object object = methodProxy.invokeSuper(o, objects);
        System.out.println("HelloMethodInterceptor: after...");
        return object;
    }
}

測試結(jié)果:

public static void main(String[] args) {
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(Hello.class);
        enhancer.setCallback(new HelloMethodInterceptor());
        Hello hello = (Hello) enhancer.create();
        hello.sayHello();
    }

HelloMethodInterceptor: before...
hi, this is Hello-Original.
HelloMethodInterceptor: after...

CGLib 細節(jié)可以參考深入理解CGLIB動態(tài)代理機制0 寫的挺不錯的

最后編輯于：2020.05.12 11:38:37

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