用过滤器来解决JSP中文乱码问题

首先写一个过滤器的类，如下：

 1 package com.util; 2  3 import java.io.IOException; 4 import java.io.UnsupportedEncodingException; 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.ServletRequest;11 import javax.servlet.ServletResponse;12 import javax.servlet.http.HttpServletRequest;13 import javax.servlet.http.HttpServletRequestWrapper;14 import javax.servlet.http.HttpServletResponse;15 import javax.servlet.http.HttpSession;16 17 18 //过滤器处理表单传到servlet的乱码问题19 public class MyFilter implements Filter{20     //自写一个request换掉原来的request,重写里面的getParemeter方法，可以设置编码21     class MyRequest extends HttpServletRequestWrapper{22         23         @Override24         public String getParameter(String param) {25             String value = null;26             try {27                 //post28                 super.setCharacterEncoding(encoding);//把编码转换为encoding29                 value = super.getParameter(param);30                 if(super.getMethod().equalsIgnoreCase("GET")){31                     if(value!=null){32                         value = new String(value.getBytes("iso8859-1"),encoding);33                     }34                 }35             } catch (UnsupportedEncodingException e) {36                 // TODO Auto-generated catch block37                 e.printStackTrace();38             }39             return value;40         }41 42         public MyRequest(HttpServletRequest request) {43             super(request);44         }45         46     }47     protected String encoding=null; 48     public void destroy() { //销毁49         // TODO Auto-generated method stub50         this.encoding=null;51     }52    //对编码问题进行转换53     public void doFilter(ServletRequest request, ServletResponse response,54             FilterChain chain) throws IOException, ServletException {55         // TODO Auto-generated method stub56         response.setContentType("text/html;charset="+encoding);57         //过滤未登录用户58         HttpServletRequest req = (HttpServletRequest) request;59         HttpServletResponse resp = (HttpServletResponse) response;60         String path=req.getServletPath();61         String param=req.getQueryString();62         if(path!=null){63             path=path+"?"+param;//全请求路径64         }65         if(path.endsWith("myAddress")||path.endsWith("myJingDong")||path.indexOf("myShouCang")!=-1||path.endsWith("updateUser")||path.indexOf("showOrder")!=-1||path.indexOf("showValidOrder")!=-1||path.indexOf("showCancelOrder")!=-1||path.indexOf("fillOrder")!=-1){66             HttpSession session = req.getSession();67             String userName = (String) session.getAttribute("username");68             if(userName == null){69                 session.setAttribute("url", path.replaceFirst("/", ""));70                 System.out.println(session.getAttribute("url"));71                 resp.sendRedirect("user.do?op=loginAction");72                 return;73             }74         }75         //把过滤器给下一个过滤器或资源处理器76         chain.doFilter(new MyRequest((HttpServletRequest) request), response); 77     }78 79     public void init(FilterConfig filterConfig) throws ServletException {80         // TODO Auto-generated method stub81         this.encoding=filterConfig.getInitParameter("encoding");//encoding在web.xml中指定82     }83 84 }

然后在web.xml对该过滤器进行注册和映射：

<filter>    <filter-name>EncodingFilter</filter-name>    <filter-class>com.util.MyFilter</filter-class>    <init-param>       <param-name>encoding</param-name>       <param-value>utf-8</param-value>    </init-param>  </filter> <filter-mapping>     <filter-name>EncodingFilter</filter-name>     <url-pattern>/*</url-pattern> </filter-mapping>

上面写的过滤器MyFilter类，本来只能处理post提交的数据(post是先处理后接收，get是先接收后处理)。

但是MyFilter里面在对任何页面过滤的时候，来了一个偷梁换柱：把原来客户端请求的request给换掉了，换成自己定义的一个request了，即内部类MyRequest，不过该类要继承一个类HttpServletRequestWrapper。

在自定义的一个内部类MyRequest里面，实现了一个好强大的功能，就是重写了request的getParameter()方法。该方法里面即处理了post提交，又能处理get提交，返回的值就是处理后的值，所以该过滤器就能实现处理post和get提交的乱码问题！