使用过滤器解决JSP页面的乱码问题

乱码详情

总结：讨论了使用GET和POST方法，控制台和JSP页面显示的问题。

最终发现：在servlet或者过滤器中添加：request.setCharacterEncoding("utf-8");

　　　　　　　　res.setContentType("text/html;charset=utf-8");

即可解决页面显示乱码问题。

JSP页面中

<%@ page language="java"

    pageEncoding="UTF-8"%>

<!DOCTYPE html>

<html>

<head>

<meta charset="UTF-8">

<title>Insert title here</title>

</head>

<body>

<form action="${pageContext.request.contextPath}/encodingServlet" method="get">  //选择GET或者POST提交

<input type="text" name="text" > <input type="submit"> </form> </body> </html>

过滤器页面：

 public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)

                   throws IOException, ServletException {

             HttpServletRequest req = (HttpServletRequest) request;

             HttpServletResponse res = (HttpServletResponse) response;

             //放行！！！——————————————————————

             chain.doFilter(newRequest, res);

      }

编写的servlet的get方法中：

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

      String str=request.getParameter("text");

      if(str!=null)System.out.println(str);

      response.getWriter().write(str);

      }

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alt="" width="287" />

我们在过滤器中注释掉

//req.setCharacterEncoding("utf-8");
// res.setContentType("text/html;charset=utf-8");

	控制台显示	JSP页面显示
GET	你好啊	???
POST	ä½ å¥½å	：浣犲ソ鍟�

在filte过滤器加上：request.setCharacterEncoding("utf-8");

　　　　　　　　res.setContentType("text/html;charset=utf-8");

	控制台显示	JSP页面显示
GET	你好啊	你好啊
POST	你好啊	你好啊

这里JSP页面出现乱码是因为：在getParameter()方法中，得到的字符串是乱码的。

在Filter中：

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)

            throws IOException, ServletException {

        HttpServletRequest req = (HttpServletRequest) request;

        HttpServletResponse res = (HttpServletResponse) response;

        //放行！！！——————————————————————

//

        EnhanceRequest newRequest=new EnhanceRequest(req);

  　　//      req.setCharacterEncoding("utf-8");

    //    res.setContentType("text/html;charset=utf-8");

        System.out.println("filtering");

        chain.doFilter(newRequest, res);

    }

使用装饰者模式，增强getParameter().

小插曲：装饰者模式：

增强类与被增强类实现统一接口。

增强类中传入被增强的类

需要增强的方法重写。

之后在Filter中增强req：

class EnhanceRequest extends HttpServletRequestWrapper {

      private HttpServletRequest request;

      public EnhanceRequest(HttpServletRequest req) {

             super(req);

             this.request=req;

      }

      //对getParameter增强

      @Override

      public String getParameter(String name) {

             String parameter =request.getParameter(name);//乱码

             try {

                   parameter=new String(parameter.getBytes("iso8859-1"),"UTF-8");

             } catch (UnsupportedEncodingException e) {

                   // TODO Auto-generated catch block

                   e.printStackTrace();

             }

             return parameter;

      }

}

	控制台显示	JSP页面显示
GET	???	???
POST	你好啊	???

同时发现：当JSP页面中去除掉这条代码contentType="text/html; charset=UTF-8"，将造成JSP页面显示数据为乱码。

结论：要解决JSP页面和控制台的乱码问题，只要在filter过滤器加上：request.setCharacterEncoding("utf-8");

　　　　　　　　res.setContentType("text/html;charset=utf-8");

或者就在servlet页面上添加：request.setCharacterEncoding("utf-8");

　　　　　　　　res.setContentType("text/html;charset=utf-8");

便可解决POST和GET方法的乱码问题。

巴特西

使用过滤器解决JSP页面的乱码问题

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