使用filter对请求设置编码

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：

 package jd.com.coding;

 import javax.servlet.*;
 import javax.servlet.annotation.WebFilter;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletRequestWrapper;
 import javax.servlet.http.HttpServletResponse;
 import java.io.IOException;

 @WebFilter(filterName = "FilterAllSeting")
 public class FilterAllSeting implements Filter {
     public void destroy() {
     }

     public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
         HttpServletRequest re=(HttpServletRequest) req;
         HttpServletResponse res=(HttpServletResponse) resp;
         chain.doFilter(new SetCoding(re), resp);
     }

     public void init(FilterConfig config) throws ServletException {
     }

 }

 class  SetCoding extends HttpServletRequestWrapper{
     private HttpServletRequest request;

     public  SetCoding(HttpServletRequest request){
         super(request);
         this.request=request;
     }

     @Override
     public String getParameter(String name) {
         String method=request.getMethod();
         String val=request.getParameter(name);
                                  if( method.equalsIgnoreCase("get"))
         {   try {
             return new String(val.getBytes("ISO_8859_1"), "UTF-8");
         }catch (IOException ex){
             ex.printStackTrace();
         }
         }

         else if(method.equalsIgnoreCase("POST")){
             try {
                 request.setCharacterEncoding("utf-8");
             }catch (IOException ex){
                 ex.printStackTrace();
             }

         }
         return super.getParameter(name);
     }
 }

最终版本：

 package cn.itcast.web.filter;

 import java.io.IOException;
 import java.io.UnsupportedEncodingException;
 import java.util.Map;

 import javax.servlet.Filter;
 import javax.servlet.FilterChain;
 import javax.servlet.FilterConfig;
 import javax.servlet.ServletException;
 import javax.servlet.ServletRequest;
 import javax.servlet.ServletResponse;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletRequestWrapper;
 import javax.servlet.http.HttpServletResponse;
 /**
  * 统一编码
  * @author Administrator
  *
  */
 public class EncodingFilter implements Filter {

     @Override
     public void init(FilterConfig filterConfig) throws ServletException {
         // TODO Auto-generated method stub

     }

     @Override
     public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws IOException, ServletException {
         //1.强转
         HttpServletRequest request=(HttpServletRequest) req;
         HttpServletResponse response=(HttpServletResponse) resp;

         //2.放行
         chain.doFilter(new MyRequest(request), response);
     }

     @Override
     public void destroy() {
         // TODO Auto-generated method stub

     }

 }
 class MyRequest extends HttpServletRequestWrapper{
     private HttpServletRequest request;
     private boolean flag=true;

     public MyRequest(HttpServletRequest request) {
         super(request);
         this.request=request;
     }

     @Override
     public String getParameter(String name) {
         if(name==null || name.trim().length()==){
             return null;
         }
         String[] values = getParameterValues(name);
         if(values==null || values.length==){
             return null;
         }

         return values[];
     }

     @Override
     /**
      * hobby=[eat,drink]
      */
     public String[] getParameterValues(String name) {
         if(name==null || name.trim().length()==){
             return null;
         }
         Map<String, String[]> map = getParameterMap();
         if(map==null || map.size()==){
             return null;
         }

         return map.get(name);
     }

     @Override
     /**
      * map{ username=[tom],password=[123],hobby=[eat,drink]}
      */
     public Map<String,String[]> getParameterMap() {  

         /**
          * 首先判断请求方式
          * 若为post  request.setchar...(utf-8)
          * 若为get 将map中的值遍历编码就可以了
          */
         String method = request.getMethod();
         if("post".equalsIgnoreCase(method)){
             try {
                 request.setCharacterEncoding("utf-8");
                 return request.getParameterMap();
             } catch (UnsupportedEncodingException e) {
                 // TODO Auto-generated catch block
                 e.printStackTrace();
             }
         }else if("get".equalsIgnoreCase(method)){
             Map<String,String[]> map = request.getParameterMap();
             if(flag){
                 for (String key:map.keySet()) {
                     String[] arr = map.get(key);
                     //继续遍历数组
                     for(int i=;i<arr.length;i++){
                         //编码
                         try {
                             arr[i]=new String(arr[i].getBytes("iso8859-1"),"utf-8");
                         } catch (UnsupportedEncodingException e) {
                             e.printStackTrace();
                         }
                     }
                 }
                 flag=false;
             }
             //需要遍历map 修改value的每一个数据的编码

             return map;
         }

         return super.getParameterMap();
     }

 }