spring中的动态代理

Posted 2020-12-11 yytxdy

spring中提供了两种动态代理的方式，分别是Java Proxy以及cglib

JavaProxy只能代理接口，而cglib是通过继承的方式，实现对类的代理

添加一个接口以及对应的实现类

public interface HelloInterface {
    void sayHello();
}

public class HelloInterfaceImpl implements HelloInterface {
    @Override
    public void sayHello() {
        System.out.println("hello");
    }
}

JavaProxy通过实现InvocationHandler实现代理

public class CustomInvocationHandler implements InvocationHandler {
    private HelloInterface helloInterface;

    public CustomInvocationHandler(HelloInterface helloInterface) {
        this.helloInterface = helloInterface;
    }

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

而cglib实现MethodInterceptor进行方法上的代理

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

}

分别实现调用代码

    public static void main(String[] args) {
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(HelloInterfaceImpl.class);
        enhancer.setCallback(new CustomMethodInterceptor());
        HelloInterface target = (HelloInterface) enhancer.create();
        target.sayHello();

        CustomInvocationHandler invocationHandler = new CustomInvocationHandler(new HelloInterfaceImpl());
        HelloInterface target2 = (HelloInterface)  Proxy.newProxyInstance(Demo.class.getClassLoader(), new Class[]{HelloInterface.class}, invocationHandler);
        target2.sayHello();
    }

可以看到对于的代理信息输出

before hello for cglib
hello
after hello for cglib
before hello for proxy
hello
after hello for proxy