intercept interceptor chain and the chain of responsibility

Disclaimer: This article is a blogger original article, shall not be reproduced without the bloggers allowed. https://blog.csdn.net/huoguang_/article/details/89238244

Examples

interface

package hello;

public interface HelloWorld {
	public void sayHelloWorld();
}

Interface

package hello;

public class HelloWorldImpl implements HelloWorld {

	@Override
	public void sayHelloWorld() {
		System.out.println("Hello World");
	}

}

 

Interceptor

interface

package interceptor;

import java.lang.reflect.Method;

public interface Interceptor {
	public boolean before(Object proxy, Object target, Method method, Object[] args);

	public void around(Object proxy, Object target, Method method, Object[] args);

	public void after(Object proxy, Object target, Method method, Object[] args);
}

Implement an interface

package interceptor;

import java.lang.reflect.Method;

public class InterceptorImpl implements Interceptor {
	@Override
	public boolean before(Object proxy, Object target, Method method, Object[] args) {
		System.err.println("反射方法前逻辑");
		return false;// 不反射被代理对象原有方法
	}

	@Override
	public void after(Object proxy, Object target, Method method, Object[] args) {
		System.err.println("反射方法后逻辑。");
	}

	@Override
	public void around(Object proxy, Object target, Method method, Object[] args) {
		System.err.println("取代了被代理对象的方法");
	}
}

Interceptor

package interceptor;

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

public class InterceptorJdkProxy implements InvocationHandler {

    private Object target; //真实对象
    private String interceptorClass = null;//拦截器全限定名
    
    public InterceptorJdkProxy(Object target, String interceptorClass) {
        this.target = target;
        this.interceptorClass = interceptorClass;
    }

    /**
     * 绑定委托对象并返回一个【代理占位】
     *
     * @param target 真实对象
     * @return 代理对象【占位】
     */
    public static Object bind(Object target, String interceptorClass) {
        //取得代理对象    
        return Proxy.newProxyInstance(target.getClass().getClassLoader(),
                target.getClass().getInterfaces(), 
                new InterceptorJdkProxy(target, interceptorClass));
    }

    @Override
    /**
     * 通过代理对象调用方法，首先进入这个方法.
     *
     * @param proxy --代理对象
     * @param method --方法，被调用方法
     * @param args -- 方法的参数
     */
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        if (interceptorClass == null) {
            //没有设置拦截器则直接反射原有方法
            return method.invoke(target, args);
        }
        Object result = null;
        //通过反射生成拦截器
        Interceptor interceptor = 
            (Interceptor) Class.forName(interceptorClass).newInstance();
        //调用前置方法
        if (interceptor.before(proxy, target, method, args)) {
            //反射原有对象方法
            result = method.invoke(target, args);
        } else {//返回false执行around方法
            interceptor.around(proxy, target, method, args);
        }
        //调用后置方法
        interceptor.after(proxy, target, method, args);
        return result;
    }
}

 

 

 

 

 

 

Chain of Responsibility

package chain;

import java.lang.reflect.Method;

import interceptor.Interceptor;

public class Interceptor1 implements Interceptor {
	public boolean before(Object proxy, Object target, Method method, Object[] args) {
		System.out.println("【拦截器1】的before方法");
		return true;
	}

	public void around(Object proxy, Object target, Method method, Object[] args) {
	}

	public void after(Object proxy, Object target, Method method, Object[] args) {
		System.out.println("【拦截器1】的after方法");
	}
}

package chain;

import java.lang.reflect.Method;

import interceptor.Interceptor;

public class Interceptor2 implements Interceptor {
    public boolean before(Object proxy, Object target, Method method, Object[] args) {
        System.out.println("【拦截器2】的before方法");
        return true;
    }
    
    public void around(Object proxy, Object target, Method method, Object[] args) {}

    public void after(Object proxy, Object target, Method method, Object[] args) {
        System.out.println("【拦截器2】的after方法");
    }
}

package chain;

import java.lang.reflect.Method;

import interceptor.Interceptor;

public class Interceptor3 implements Interceptor {
    public boolean before(Object proxy, Object target, Method method, Object[] args) {
        System.out.println("【拦截器3】的before方法");
        return true;
    }
    
    public void around(Object proxy, Object target, Method method, Object[] args) {}

    public void after(Object proxy, Object target, Method method, Object[] args) {
        System.out.println("【拦截器3】的after方法");
    }
}

 

 

test

package Interceptortest;

import hello.HelloWorld;
import hello.HelloWorldImpl;
import interceptor.InterceptorJdkProxy;

public class TestInterceptor {
	public static void main(String[] args) {
		testInterceptor();
//		testChain();
	}
	
	
	public static void testInterceptor() {
		HelloWorld proxy = (HelloWorld) InterceptorJdkProxy.bind(new HelloWorldImpl(), "interceptor.InterceptorImpl");
		proxy.sayHelloWorld();
	}
	
	public static void testChain() {
		HelloWorld proxy1 = (HelloWorld) InterceptorJdkProxy.bind(new HelloWorldImpl(), "chain.Interceptor1");
        HelloWorld proxy2 = (HelloWorld) InterceptorJdkProxy.bind(proxy1, "chain.Interceptor2");
        HelloWorld proxy3 = (HelloWorld) InterceptorJdkProxy.bind(proxy2, "chain.Interceptor3");
        proxy3.sayHelloWorld();
	}
}