下面的任何一条缺一不可，注意，我之所以全部都用的XXX，意思就是这几个最好全部都一致！

1、HTML中要用meta content="text/html; charset=XXX"来指出HTML页面的编码为XXX，XXX必须和HTML文件本身的编码一致！

2、JSP页面中必须要出现pageEncoding="XXX"用来指出JSP文件本身的编码，这样JSP文件在编译为java文件的时候才不会有乱码（并且JSP文件对应的java文件是UTF-8的编码），然后JSP文件对应的java文件被编译为class文件，仍然是UTF-8编码，最后class文件被web-container（例如tomcat）执行，得到的结果tomcat会给返回到客户端浏览器上，这时就需要contentType="...; charset=XXX"来指定编码；如果是contentType="text/html"，也可以用meta来指定charset=XXX，

3、JSP和Servlet中，必须确保在用request取出参数之前调用request.setCharacterEncoding("XXX")，这个如果不希望重复写这个代码，就采取在filter中写上这个代码

4、response.setCharacterEncoding和response.setContentType()暂时不明真相

比如下面有个测试的典型，input.html, input.jsp，这些页面的pageEncoding,charset都事先写在代码里了，一个不缺，并且文件本身的编码与之一致，然后你可以看看打开、关闭filter的效果有什么不同

文件结构如下

/WebContent/WEB-INF/web.xml

/WebContent/9.10.3/input.html

/WebContent/9.10.3/input.jsp

 

web.xml

         
             
      
       foo-servlet2
              
      
                   org.lxh.servletdemo.FooServlet2        
          
         
             
      
       foo-servlet2
              
      
       /FooServlet2
          
             
             
              
      
       charset-encoding
               
      
       org.lxh.filterdemo.CharacterEncodingFilter
               
                   
       
        encoding
                    
       
        UTF-8
                
               
                   
       
        enable
                    
       
        true
                
           
         
             
      
       charset-encoding
              
      
       /*
          
     

input.html

         
     
        
              请输入要显示的内容：
              
          
     

input.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%>
         
         <%        String str = (String) request.getAttribute("info") ;        out.println("
"+str+"
") ;    %>

FooServlet2.java

package org.lxh.servletdemo;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.*;public class FooServlet2 extends HttpServlet {    @Override    public void doGet(HttpServletRequest req, HttpServletResponse resp)            throws ServletException, IOException {        // 在这里也没有调用request.setCharacterEncoding()，        // 你把CharacterEncodingFilter关闭了试试，看看结果有什么        // 不一样        String info = req.getParameter("info");        if (info != null) {            info = info + "--- 这是一条小尾巴";            System.out.println(this + ", " + info);            req.setAttribute("info", info);            req.getRequestDispatcher("/9.10.3/input.jsp").forward(req, resp);        }    }    @Override    public void doPost(HttpServletRequest req, HttpServletResponse resp)            throws ServletException, IOException {        this.doGet(req, resp);    }}

CharacterEncodingFilter.java

package org.lxh.filterdemo;import java.io.IOException;import java.nio.charset.Charset;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.HttpServletResponse;public class CharacterEncodingFilter implements Filter {    protected String encoding = null;     protected FilterConfig filterConfig = null;     protected boolean enable = false;     public void destroy() {         this.encoding = null;         this.filterConfig = null;     }     public void doFilter(ServletRequest request, ServletResponse response,                            FilterChain chain) throws IOException, ServletException {         if (this.enable) {            String encoding = this.selectEncoding(request);             if (encoding != null && !encoding.equals("")) {                 System.out.println(this + ": " + encoding);                request.setCharacterEncoding(encoding); //Overrides the name of the character encoding used in the body of this request. This method must be called prior to reading request parameters or reading input using getReader().                // response.setCharacterEncoding(encoding); // 暂时不太清楚            }        }        // Pass control on to the next filter         chain.doFilter(request, response);      }      public void init(FilterConfig filterConfig) throws ServletException {          this.filterConfig = filterConfig;          this.encoding = filterConfig.getInitParameter("encoding");         if (!Charset.isSupported(encoding)) {            encoding = null;         }         String enableString = filterConfig.getInitParameter("enable");         if (enableString.equalsIgnoreCase("true")) {            this.enable = true;         } else {            this.enable = false;         }      }       protected String selectEncoding(ServletRequest request) {           return (this.encoding);       } }