練習時只做了對request 的處理，這裏記錄一下，filter 對 response的處理。

原文地址：java使用Filter過濾器對Response返回值進行修改

有時候在開發過程中會有這樣一個場景，有時需要對返回的數據進行處理。比如加密啊，添加某些標記啊等等。這種情況我們可以通過過濾器去處理。

過濾器是什麽就不介紹了，百度一下，你就知道。

以下是代碼：

返回值輸出代理類：這個類主要是為了吧Response裏面的返回值獲取到，因為直接Response沒有提供直接拿到返回值的方法。所以要通過代理來取得返回值

 1 package com.channel.filter;
 2  
 3  
 4 import java.io.ByteArrayOutputStream;
 5 import java.io.IOException;
 6  
 7 import javax.servlet.ServletOutputStream;
 8 import javax.servlet.WriteListener;
 9 import javax.servlet.http.HttpServletResponse;
10 import javax.servlet.http.HttpServletResponseWrapper;
11  
12  
13 /**
14  * 返回值輸出代理類
15  * 
16  * @Title: ResponseWrapper
17  * @Description:
18  * @author kokJuis
19  * @date 上午9:52:11
20  */
21 public class ResponseWrapper extends HttpServletResponseWrapper
22 {
23  
24     private ByteArrayOutputStream buffer;
25  
26     private ServletOutputStream out;
27  
28     public ResponseWrapper(HttpServletResponse httpServletResponse)
29     {
30         super(httpServletResponse);
31         buffer = new ByteArrayOutputStream();
32         out = new WrapperOutputStream(buffer);
33     }
34  
35     @Override
36     public ServletOutputStream getOutputStream()
37         throws IOException
38     {
39         return out;
40     }
41  
42     @Override
43     public void flushBuffer()
44         throws IOException
45     {
46         if (out != null)
47         {
48             out.flush();
49         }
50     }
51  
52     public byte[] getContent()
53         throws IOException
54     {
55         flushBuffer();
56         return buffer.toByteArray();
57     }
58  
59     class WrapperOutputStream extends ServletOutputStream
60     {
61         private ByteArrayOutputStream bos;
62  
63         public WrapperOutputStream(ByteArrayOutputStream bos)
64         {
65             this.bos = bos;
66         }
67  
68         @Override
69         public void write(int b)
70             throws IOException
71         {
72             bos.write(b);
73         }
74  
75         @Override
76         public boolean isReady()
77         {
78  
79             // TODO Auto-generated method stub
80             return false;
81  
82         }
83  
84         @Override
85         public void setWriteListener(WriteListener arg0)
86         {
87  
88             // TODO Auto-generated method stub
89  
90         }
91     }
92  
93 }

過濾器類：

 1 package com.channel.filter;
 2  
 3  
 4 import java.io.IOException;
 5  
 6 import javax.servlet.Filter;
 7 import javax.servlet.FilterChain;
 8 import javax.servlet.FilterConfig;
 9 import javax.servlet.ServletException;
10 import javax.servlet.ServletOutputStream;
11 import javax.servlet.ServletRequest;
12 import javax.servlet.ServletResponse;
13 import javax.servlet.http.HttpServletResponse;
14  
15 import com.channel.util.RsaEncryptUtil;
16  
17  
18 /**
19  * 返回值輸出過濾器，這裏用來加密返回值
20  * 
21  * @Title: ResponseFilter
22  * @Description:
23  * @author kokJuis
24  * @date 上午9:52:42
25  */
26 public class ResponseFilter implements Filter
27 {
28  
29     @Override
30     public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain)
31         throws IOException, ServletException
32     {
33         ResponseWrapper wrapperResponse = new ResponseWrapper((HttpServletResponse)response);//轉換成代理類
34         // 這裏只攔截返回，直接讓請求過去，如果在請求前有處理，可以在這裏處理
35         filterChain.doFilter(request, wrapperResponse);
36         byte[] content = wrapperResponse.getContent();//獲取返回值
37     //判斷是否有值
38         if (content.length > 0)
39         {
40  
41             String str = new String(content, "UTF-8");
42             System.out.println("返回值:" + str);
43             String ciphertext = null;
44  
45             try
46             {
47                 //......根據需要處理返回值
48             }
49             catch (Exception e)
50             {
51                 e.printStackTrace();
52             }
53         //把返回值輸出到客戶端
54             ServletOutputStream out = response.getOutputStream();
55             out.write(ciphertext.getBytes());
56             out.flush();
57         }
58  
59     }
60  
61     @Override
62     public void init(FilterConfig arg0)
63         throws ServletException
64     {
65  
66     }
67  
68     @Override
69     public void destroy()
70     {
71  
72     }
73  
74 }

配置很簡單：

spring boot：

 1  　　/**
 2      * 配置過濾器，這裏過濾器主要是對返回值做後繼處理
 3      * 
 4      * @return
 5      */
 6     @Bean
 7     public FilterRegistrationBean someFilterRegistration()
 8     {
 9         FilterRegistrationBean registration = new FilterRegistrationBean();
10         registration.setFilter(new ResponseFilter());// 配置一個返回值加密過濾器
11         registration.addUrlPatterns("/*");
12         registration.addInitParameter("paramName", "paramValue");
13         registration.setName("responseFilter");
14         return registration;
15     }

spring mvc 下直接在web.xml下添加配置即可

 1 <!-- 返回值過濾器 -->
 2     <filter>
 3         <filter-name>responseFilter</filter-name>
 4         <filter-class>com.im.filter.ResponseFilter</filter-class>
 5     </filter>
 6  
 7     <filter-mapping>
 8         <filter-name>responseFilter</filter-name>
 9         <url-pattern>/*</url-pattern>
10     </filter-mapping>

java使用Filter過濾器對Response返回值進行修改