责任链模式(ChainOfResponsibiliby、Filter)

Request 类:

 package com.demo;

 public class Request {

     private String requestStr;

     public String getRequestStr() {
         return requestStr;
     }

     public void setRequestStr(String requestStr) {
         this.requestStr = requestStr;
     }

 }

Response 类:

 package com.demo;

 public class Response {

     private String responseStr;

     public String getResponseStr() {
         return responseStr;
     }

     public void setResponseStr(String responseStr) {
         this.responseStr = responseStr;
     }

 }

Filter 接口:

 package com.demo;

 public interface Filter {
     void doFilter(Request request,Response response,FilterChain chain);
 }

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:

 package com.demo;

 import java.util.ArrayList;

 public class FilterChain implements Filter{

     //过滤器链
     private ArrayList<Filter> chain = new ArrayList<Filter>();

     //过滤器链的索引
     int index = 0;

     //往过滤器链中添加过滤器
     public ArrayList<Filter> add(Filter filter){
         chain.add(filter);
         return chain;
     }

     /**
      * 重写 doFilter方法
      * 如果没有遍历完，调用特定过滤器的doFilter方法
      */
     @Override
     public void doFilter(Request request, Response response, FilterChain chain) {
         //如果遍历完过滤器链，则返回
         if(index == this.chain.size()) return;

         Filter filter = this.chain.get(index);
         index ++;
         filter.doFilter(request, response, chain);
     }

 }

HTMLFilter (Fiter接口的实现类):

 package com.demo;

 public class HTMLFilter implements Filter {

     @Override
     public void doFilter(Request request, Response response, FilterChain chain) {
         //处理过滤器该干的事情
         request.setRequestStr(request.getRequestStr().replace('<', '[').replace('>', ']')
                 + "---HTMLFilter()");

         //跳往下一个过滤器
         chain.doFilter(request, response, chain);

         //回调
         response.setResponseStr(response.getResponseStr() + "---HTMLFilter()");
     }

 }

SensitiveFilter (Fiter接口的实现类):

 package com.demo;

 public class SensitiveFilter implements Filter {

     @Override
     public void doFilter(Request request, Response response, FilterChain chain) {
         //处理过滤器该干的事情
         request.setRequestStr(request.getRequestStr().replace("被就业", "就业").replace("敏感", "")
                 + "---SensitiveFilter()");

         //跳往下一个过滤器
         chain.doFilter(request, response, chain);

         //回调
         response.setResponseStr(response.getResponseStr() + "---SensitiveFilter()");
     }

 }

Main 执行过滤器操作的类:

 package com.demo;

 public class Main {
     public static void main(String[] args) {
         //请求信息
         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";

         //实例化Request对象
         Request request = new Request();
         request.setRequestStr(msg);

         //实例化Response对象
         Response response = new Response();
         response.setResponseStr("response");

         //过滤器链
         FilterChain chain = new FilterChain();
         chain.add(new HTMLFilter()).add(new SensitiveFilter());

         //开始过滤
         chain.doFilter(request, response, chain);

         //打印处理结果
         System.out.println(request.getRequestStr());
         System.out.println(response.getResponseStr());

     }
 }

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