Java 动态代理

前言

关于动态代理

JDK动态代理

public class JDKProxy implements InvocationHandler {

    private Object target;

    public JDKProxy(Object target) {
        this.target = target;
    }

    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("before do something");
        method.invoke(target, args);
        System.out.println("after do something");
        return proxy;
    }
}

public class ProxyPratice {

    public static void main(String[] args) {

        ProxyTarget proxyTarget = new ProxyTarget();
        //JDK代理
        ProxyInterface proxyInterface = (ProxyInterface) Proxy.newProxyInstance(ProxyPratice.class.getClassLoader(), new Class[]{ProxyInterface.class}, new JDKProxy(proxyTarget));
        proxyInterface.doSomething();
    }
}

CGLIB动态代理

public class CglibProxy implements MethodInterceptor {

    private Object target;

    public CglibProxy(Object target) {
        this.target = target;
    }

    @Override
    public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
        System.out.println("before do something");
        method.invoke(target, objects);
        System.out.println("after do something");
        return null;
    }   
}

public class ProxyPratice {

    public static void main(String[] args) {

        ProxyTarget proxyTarget = new ProxyTarget();
        //CGLIB
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(ProxyInterface.class);
        enhancer.setCallback(new CglibProxy(proxyTarget));
        ProxyInterface proxyInterface2 = (ProxyInterface)enhancer.create();
        proxyInterface2.doSomething();
    }
}

区别

java动态代理是利用反射机制生成一个实现代理接口的匿名类，在调用具体方法前调用InvokeHandler来处理。所以只能对实现了接口的类生成代理，而不能针对类。

cglib动态代理是利用asm开源包，对代理对象类的class文件加载进来，通过修改其字节码生成子类来处理，覆盖其中的方法（继承）。所以CGLib不能对声明为final的方法进行代理。