java設計模式--責任鏈模式

責任鏈模式：將能夠處理同一類請求的對象連成一條鏈，如果不能處理則傳遞給鏈上的下一個對象。

//請假對象
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;
    }

}

//抽象類
public abstract class Leader {
    
    String name;
    
    Leader nextLeader;

    public Leader(String name) {
        this.name = name;
    }

    public void setNextLeader(Leader nextLeader) {
        this.nextLeader = nextLeader;
    }
    
    //設置責任鏈的處理對象（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("員工請假小於3天");
            System.out.println("審批通過");
        }else{
            if(this.nextLeader!=null){
                this.nextLeader.handleRequest(qingjiaRequest);
            }
        }
        
        
    }

}

//經理
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("經理審批通過");
        }else{
             //經理處理后的邏輯
        }
        
        
    }

}

public static void main(String[] args) {
        
        QingjiaRequest qingjiaRequest = new QingjiaRequest("張三", 2, "請假");
        //QingjiaRequest qingjiaRequest1 = new QingjiaRequest("張三", 5, "請假");
        Leader a = new Zhuren("張主任");
        Leader b = new Manager("王經理");
        //可以用一個容器對象責任鏈對象進行一些封裝
        a.setNextLeader(b);
        //開始請假
        a.handleRequest(qingjiaRequest);
        
    }

應用場景：try catch,javascript 冒泡，servlet filter,struts2 攔截器

 

模仿 JavaWeb 中的 Filter，可以對其思路有個很好的把握
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());

        // 先執行所有request再倒序執行所有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;

    // 鏈式調用
    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 測試

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);
    }

}