InvocationHandler is the interface implemented by the invocation handler of a proxy instance.

Each proxy instance has an associated invocation handler. When a method is invoked on a proxy instance, the method invocation is encoded and dispatched to the invoke method of its invocation handler.

package cn.zno.newstar.base.utils.text;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

public class ProxyDemo {
    public static void main(String[] args) {
        Target target = new TargetImpl();
        TargetIH ih = new TargetIH();
        Target proxy 
 
= ih.newProxyInstance(target);
        proxy.doSomething();
        proxy.doSomethingElse();
    }
}

interface Target {
    void doSomething();

    void doSomethingElse();
}

class TargetImpl implements Target {

    @Override
    public void doSomething() {
        System.out.println("TargetImpl doSomething");
    }

    @Override
    
 
public void doSomethingElse() {
        System.out.println("TargetImpl doSomethingElse");
    }
}

class TargetIH implements InvocationHandler {
    private Object target;

    @SuppressWarnings("unchecked")
    public <T> T newProxyInstance(T target) {
        this.target = target;
        Class<?> clazz = target.getClass();
        // a proxy instance 的 invocation handler 實現 InvocationHandler 介面
        return (T) Proxy.newProxyInstance(clazz.getClassLoader(), clazz.getInterfaces(), this);
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) {
        System.out.println("proxy start");
        Object result = null;
        /* 
         * 這裡可以正則方法名，判斷引數，判斷註解；不同場景動態代理不同的事
         * 
         * */
        try {
            result = method.invoke(target, args);
        } catch (Exception e) {
            // do something
        }
        System.out.println("proxy end");
        return result;
    }
}

結果：

proxy start
TargetImpl doSomething
proxy end
proxy start
TargetImpl doSomethingElse
proxy end