责任链模式：将能够处理同一类请求的对象连成一条链，如果不能处理则传递给链上的下一个对象。

//请假对象public class QingjiaRequest {        private String name;        private int days;        private String reason;    public QingjiaRequest(String name, int days, String reason) {        this.name = name;        this.days = days;        this.reason = reason;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public int getDays() {        return days;    }    public void setDays(int days) {        this.days = days;    }    public String getReason() {        return reason;    }    public void setReason(String reason) {        this.reason = reason;    }}

//抽象类public abstract class Leader {        String name;        Leader nextLeader;    public Leader(String name) {        this.name = name;    }    public void setNextLeader(Leader nextLeader) {        this.nextLeader = nextLeader;    }        //设置责任链的处理对象（核心）    public abstract void handleRequest(QingjiaRequest qingjiaRequest);}

//主任public class Zhuren extends Leader{    public Zhuren(String name){        super(name);    }            public void handleRequest(QingjiaRequest qingjiaRequest) {        if(qingjiaRequest.getDays()<3){            System.out.println("员工请假小于3天");            System.out.println("审批通过");        }else{            if(this.nextLeader!=null){                this.nextLeader.handleRequest(qingjiaRequest);            }        }                    }}

//经理public class Manager extends Leader{    public Manager(String name){        super(name);    }            public void handleRequest(QingjiaRequest qingjiaRequest) {        if(qingjiaRequest.getDays()<10&&qingjiaRequest.getDays()>3){            System.out.println("经理审批通过");        }else{             //经理处理后的逻辑        }                    }}

public static void main(String[] args) {                QingjiaRequest qingjiaRequest = new QingjiaRequest("张三", 2, "请假");        //QingjiaRequest qingjiaRequest1 = new QingjiaRequest("张三", 5, "请假");        Leader a = new Zhuren("张主任");        Leader b = new Manager("王经理");         //可以用一个容器对象责任链对象进行一些封装        a.setNextLeader(b);        //开始请假        a.handleRequest(qingjiaRequest);            }

应用场景：try catch,javascript 冒泡，servlet filter,struts2 拦截器

 

模仿 JavaWeb 中的 Filter，可以对其思路有个很好的把握

1.Filter

package com.cun.filters;

import com.cun.main.FilterChain;

import com.cun.main.Request;

import com.cun.main.Response;

public interface Filter {

    void doFilter(Request request, Response response, FilterChain chain);

}

 

2.FirstFilter

package com.cun.filters;

import com.cun.main.FilterChain;

import com.cun.main.Request;

import com.cun.main.Response;

public class FirstFilter implements Filter {

    @Override

    public void doFilter(Request request, Response response, FilterChain chain) {

        request.doSomething(this.getClass().getName());

        // 先执行所有request再倒序执行所有response

        chain.doFilter(request, response, chain);

        response.doSomething(this.getClass().getName());

    }

}

3.SecondFilter

package com.cun.filters;

import com.cun.main.FilterChain;

import com.cun.main.Request;

import com.cun.main.Response;

public class SecondFilter implements Filter {

    @Override

    public void doFilter(Request request, Response response, FilterChain chain) {

        request.doSomething(this.getClass().getName());

        chain.doFilter(request, response, chain);

        response.doSomething(this.getClass().getName());

    }

}

  

3.ThirdFilter

package com.cun.filters;

import com.cun.main.FilterChain;

import com.cun.main.Request;

import com.cun.main.Response;

public class ThirdFilter implements Filter {

    @Override

    public void doFilter(Request request, Response response, FilterChain chain) {

        request.doSomething(this.getClass().getName());

        chain.doFilter(request, response, chain);

        response.doSomething(this.getClass().getName());

    }

}

4.Request

package com.cun.main;

public class Request {

    public void doSomething(String str) {

        System.out.println("Request ---> " + str);

    }

}

5.Response

package com.cun.main;

public class Response {

    public void doSomething(String str) {

        System.out.println("Response ---> " + str);

    }

}

  

6.FilterChain

package com.cun.main;

import com.cun.filters.Filter;

import java.util.ArrayList;

import java.util.List;

public class FilterChain implements Filter {

    private List<Filter> filters = new ArrayList<Filter>();

    private int index = 0;

    // 链式调用

    public FilterChain addFilter(Filter filter) {

        this.filters.add(filter);

        return this;

    }

    @Override

    public void doFilter(Request request, Response response, FilterChain chain) {

        if (index == filters.size()) {

            return;

        }

        Filter filter = filters.get(index);

        index++;

        filter.doFilter(request, response, chain);

    }

}

   

7.FilterTest 测试

package com.cun.main;

import com.cun.filters.FirstFilter;

import com.cun.filters.SecondFilter;

import com.cun.filters.ThirdFilter;

import org.junit.Test;

public class FilterTest {

    @Test

    public void Test(){

        FilterChain filterChain = new FilterChain();

        filterChain.addFilter(new FirstFilter()).addFilter(new SecondFilter()).addFilter(new ThirdFilter());

        filterChain.doFilter(new Request(),new Response(),filterChain);

    }

}