责任链模式(ChainOfResponsibiliby、Filter)

Request 类:

 1 package com.demo;
 2 
 3 public class Request {
 4     
 5     private String requestStr;
 6 
 7     public String getRequestStr() {
 8         return requestStr;
 9     }
10 
11     public void setRequestStr(String requestStr) {
12         this.requestStr = requestStr;
13     }
14 
15 }

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Response 类:

 1 package com.demo;
 2 
 3 public class Response {
 4     
 5     private String responseStr;
 6 
 7     public String getResponseStr() {
 8         return responseStr;
 9     }
10 
11     public void setResponseStr(String responseStr) {
12         this.responseStr = responseStr;
13     }
14     
15 }

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Filter 接口:

1 package com.demo;
2 
3 public interface Filter {
4     void doFilter(Request request,Response response,FilterChain chain);
5 }

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FilterChain 类，实现Filter接口，重写doFilter()方法，用来遍历过滤器链中所有的filter:

 1 package com.demo;
 2 
 3 import java.util.ArrayList;
 4 
 5 public class FilterChain implements Filter{
 6     
 7     //过滤器链
 8     private ArrayList<Filter> chain = new ArrayList<Filter>();
 9     
10     //过滤器链的索引
11     int index = 0;
12     
13     //往过滤器链中添加过滤器
14     public ArrayList<Filter> add(Filter filter){
15         chain.add(filter);
16         return chain;
17     }
18     
19     /**
20      * 重写 doFilter方法
21      * 如果没有遍历完，调用特定过滤器的doFilter方法
22      */
23     @Override
24     public void doFilter(Request request, Response response, FilterChain chain) {
25         //如果遍历完过滤器链，则返回
26         if(index == this.chain.size()) return;
27         
28         Filter filter = this.chain.get(index);
29         index ++;
30         filter.doFilter(request, response, chain);
31     }
32     
33 }

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HTMLFilter (Fiter接口的实现类):

 1 package com.demo;
 2 
 3 public class HTMLFilter implements Filter {
 4 
 5     @Override
 6     public void doFilter(Request request, Response response, FilterChain chain) {
 7         //处理过滤器该干的事情
 8         request.setRequestStr(request.getRequestStr().replace('<', '[').replace('>', ']')
 9                 + "---HTMLFilter()");
10         
11         //跳往下一个过滤器
12         chain.doFilter(request, response, chain);
13         
14         //回调
15         response.setResponseStr(response.getResponseStr() + "---HTMLFilter()");
16     }
17 
18 }

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SensitiveFilter (Fiter接口的实现类):

 1 package com.demo;
 2 
 3 public class SensitiveFilter implements Filter {
 4 
 5     @Override
 6     public void doFilter(Request request, Response response, FilterChain chain) {
 7         //处理过滤器该干的事情
 8         request.setRequestStr(request.getRequestStr().replace("被就业", "就业").replace("敏感", "") 
 9                 + "---SensitiveFilter()");
10         
11         //跳往下一个过滤器
12         chain.doFilter(request, response, chain);
13         
14         //回调
15         response.setResponseStr(response.getResponseStr() + "---SensitiveFilter()");
16     }
17 
18 }

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Main 执行过滤器操作的类:

 1 package com.demo;
 2 
 3 public class Main {
 4     public static void main(String[] args) {
 5         //请求信息
 6         String msg = "大家好:)，<script>，敏感，被就业，网络授课没感觉，因为看不见大家伙儿";
 7         
 8         //实例化Request对象
 9         Request request = new Request();
10         request.setRequestStr(msg);
11         
12         //实例化Response对象
13         Response response = new Response();
14         response.setResponseStr("response");
15         
16         //过滤器链
17         FilterChain chain = new FilterChain();
18         chain.add(new HTMLFilter()).add(new SensitiveFilter());
19         
20         //开始过滤
21         chain.doFilter(request, response, chain);
22         
23         //打印处理结果
24         System.out.println(request.getRequestStr());
25         System.out.println(response.getResponseStr());
26         
27     }
28 }

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思路：

　　在操作类中调用过滤器链的doFilter方法后，开始遍历过滤器;

　　当每执行完该过滤器的操作后马上chain.doFilter()方法跳往下一个filter，

　　当然，下一个filter的操作思路也是一致的，直至所有的request做完后，过滤器链返回；

　　所有的filter 接着执行doFiter之后的response操作了，而且是逆序的。这样就实现了过滤器的顺着进来，逆着出去的操作。

　　如果不是很清楚，用debug模式进行调试，从main方法的doFilter开始。

代码：http://pan.baidu.com/s/1kUGVy2F 提取码：9q6z