使用filter对请求设置编码

Posted 2020-10-29 evil_liu

一、复习

加强方法：

1）继承

2）装饰模式

3）动态代理。

使用装饰模式：

1）要求装饰者和被装饰者实现同一个接口或者继承同一个类。

2）装饰者要求被装饰者的引用。

3）对于要加强的方法进行加强，对于不需要的加强，执行原先的方法。

二、需求分析

1）使用filter来对所有的请求进行过滤。需要设置的url-pattern设置成/* 并且位置是在所有的filter的过滤器（filter-mapping）的前面。

2)对原先的方法进行加强。

　　1、加强的方法---request类-->通过filter的放行方法 重写request。

自己写的版本：

 1 package jd.com.coding;
 2 
 3 import javax.servlet.*;
 4 import javax.servlet.annotation.WebFilter;
 5 import javax.servlet.http.HttpServletRequest;
 6 import javax.servlet.http.HttpServletRequestWrapper;
 7 import javax.servlet.http.HttpServletResponse;
 8 import java.io.IOException;
 9 
10 @WebFilter(filterName = "FilterAllSeting")
11 public class FilterAllSeting implements Filter {
12     public void destroy() {
13     }
14 
15     public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
16         HttpServletRequest re=(HttpServletRequest) req;
17         HttpServletResponse res=(HttpServletResponse) resp;
18         chain.doFilter(new SetCoding(re), resp);
19     }
20 
21     public void init(FilterConfig config) throws ServletException {
22     }
23 
24 }
25 
26 class  SetCoding extends HttpServletRequestWrapper{
27     private HttpServletRequest request;
28 
29 
30     public  SetCoding(HttpServletRequest request){
31         super(request);
32         this.request=request;
33     }
34 
35     @Override
36     public String getParameter(String name) {
37         String method=request.getMethod();
38         String val=request.getParameter(name);
39        40        41         42         if( method.equalsIgnoreCase("get"))
43         {   try {
44             return new String(val.getBytes("ISO_8859_1"), "UTF-8");
45         }catch (IOException ex){
46             ex.printStackTrace();
47         }
48         }
49 
50         else if(method.equalsIgnoreCase("POST")){
51             try {
52                 request.setCharacterEncoding("utf-8");
53             }catch (IOException ex){
54                 ex.printStackTrace();
55             }
56 
57         }
58         return super.getParameter(name);
59     }
60 }

最终版本：

  1 package cn.itcast.web.filter;
  2 
  3 import java.io.IOException;
  4 import java.io.UnsupportedEncodingException;
  5 import java.util.Map;
  6 
  7 import javax.servlet.Filter;
  8 import javax.servlet.FilterChain;
  9 import javax.servlet.FilterConfig;
 10 import javax.servlet.ServletException;
 11 import javax.servlet.ServletRequest;
 12 import javax.servlet.ServletResponse;
 13 import javax.servlet.http.HttpServletRequest;
 14 import javax.servlet.http.HttpServletRequestWrapper;
 15 import javax.servlet.http.HttpServletResponse;
 16 /**
 17  * 统一编码
 18  * @author Administrator
 19  *
 20  */
 21 public class EncodingFilter implements Filter {
 22 
 23     @Override
 24     public void init(FilterConfig filterConfig) throws ServletException {
 25         // TODO Auto-generated method stub
 26 
 27     }
 28 
 29     @Override
 30     public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws IOException, ServletException {
 31         //1.强转
 32         HttpServletRequest request=(HttpServletRequest) req;
 33         HttpServletResponse response=(HttpServletResponse) resp;
 34         
 35         //2.放行
 36         chain.doFilter(new MyRequest(request), response);
 37     }
 38 
 39     @Override
 40     public void destroy() {
 41         // TODO Auto-generated method stub
 42 
 43     }
 44 
 45 }
 46 class MyRequest extends HttpServletRequestWrapper{
 47     private HttpServletRequest request;
 48     private boolean flag=true;
 49     
 50     
 51     public MyRequest(HttpServletRequest request) {
 52         super(request);
 53         this.request=request;
 54     }
 55     
 56     @Override
 57     public String getParameter(String name) {  
 58         if(name==null || name.trim().length()==0){
 59             return null;
 60         }
 61         String[] values = getParameterValues(name);
 62         if(values==null || values.length==0){
 63             return null;
 64         }
 65         
 66         return values[0];
 67     }
 68     
 69     @Override
 70     /**
 71      * hobby=[eat,drink]
 72      */
 73     public String[] getParameterValues(String name) {
 74         if(name==null || name.trim().length()==0){
 75             return null;
 76         }
 77         Map<String, String[]> map = getParameterMap();
 78         if(map==null || map.size()==0){
 79             return null;
 80         }
 81         
 82         return map.get(name);
 83     }
 84     
 85     @Override
 86     /**
 87      * map{ username=[tom],password=[123],hobby=[eat,drink]}
 88      */
 89     public Map<String,String[]> getParameterMap() {  
 90         
 91         /**
 92          * 首先判断请求方式
 93          * 若为post  request.setchar...(utf-8)
 94          * 若为get 将map中的值遍历编码就可以了
 95          */
 96         String method = request.getMethod();
 97         if("post".equalsIgnoreCase(method)){
 98             try {
 99                 request.setCharacterEncoding("utf-8");
100                 return request.getParameterMap();
101             } catch (UnsupportedEncodingException e) {
102                 // TODO Auto-generated catch block
103                 e.printStackTrace();
104             }
105         }else if("get".equalsIgnoreCase(method)){
106             Map<String,String[]> map = request.getParameterMap();
107             if(flag){
108                 for (String key:map.keySet()) {
109                     String[] arr = map.get(key);
110                     //继续遍历数组
111                     for(int i=0;i<arr.length;i++){
112                         //编码
113                         try {
114                             arr[i]=new String(arr[i].getBytes("iso8859-1"),"utf-8");
115                         } catch (UnsupportedEncodingException e) {
116                             e.printStackTrace();
117                         }
118                     }
119                 }
120                 flag=false;
121             }
122             //需要遍历map 修改value的每一个数据的编码
123             
124             return map;
125         }
126         
127         return super.getParameterMap();
128     }
129     
130 }