使用filter解决request.getParameter的中文乱码问题

注意：一般一个站点的所有页面的编码，包括数据库编码都要保持一致，下面默认的编码都是UTF-8

----------------------------------例1：直接提交到jsp页面----------------------------------

input_info.html

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
    <form action="display_info.jsp" method="post">
        <!-- 输入中文来测试 -->
        请输入要显示的内容：<input type="text" name="info">
        <input type="submit" value="显示">
    </form>
</body>
</html>

display_info.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
    <!--
        注意这里并没有调用request.setCharacterEncoding()，
        你把CharacterEncodingFilter关闭了试试，看看结果有什么
        不一样
    -->
    <%
        String str = (String) request.getParameter("info");
    %>
    <h1><%=str%></h1>
</body>
</html>

CharacterEncodingFilter.java

　　charset参数是从web.xml中配置好的，这里读取进来

 1 public final class CharacterEncodingFilter implements Filter {
 2     private String encoding = null; 
 3     private boolean enable = false; 
 4     public void destroy() { 
 5         this.encoding = null; 
 6     } 
 7     /**
 8      * 完成request.setCharacterEncoding(encoding);
 9      */
10     public void doFilter(ServletRequest request, ServletResponse response, 
11                            FilterChain chain) throws IOException, ServletException { 
12         if (this.enable) {
13             String encoding = this.selectEncoding(request); 
14             if (encoding != null && !encoding.equals("")) { 
15                 request.setCharacterEncoding(encoding);
16             }
17         }
18         // Pass control on to the next filter 
19         chain.doFilter(request, response);
20         // After other filters are done:
21         if (this.enable) {
22             String encoding = this.selectEncoding(request); 
23             if (encoding != null && !encoding.equals("")) {
24                 // response.setCharacterEncoding(encoding); // 实验证明这货没起什么作用，所以，不要也行
25             }
26         }
27      } 
28      /**
29       * 读取encoding参数以及enable参数，enable参数与encoding的功能无关，只是用来启用或者停用这个filter的
30       */
31     public void init(FilterConfig filterConfig) throws ServletException {
32         this.encoding = filterConfig.getInitParameter("encoding");
33         if (!Charset.isSupported(encoding)) {
34             encoding = null; // 如果不支持的话，只能选择默认的encoding了，这个filter就不起作用
35         }
36         // 读取enable参数
37         String enableString = filterConfig.getInitParameter("enable");
38         if (enableString.equalsIgnoreCase("true")) {
39             this.enable = true;
40         } else {
41             this.enable = false;
42         }
43     }
44 }

web.xml

 1     <filter> 
 2         <filter-name>charset-encoding</filter-name> 
 3         <filter-class>org.foo.filterdemo.CharacterEncodingFilter</filter-class> 
 4         <init-param> 
 5             <param-name>encoding</param-name> 
 6             <param-value>UTF-8</param-value> 
 7         </init-param> 
 8         <init-param> 
 9             <param-name>enable</param-name> 
10             <param-value>true</param-value> 
11         </init-param> 
12     </filter>
13     <filter-mapping>
14         <filter-name>charset-encoding</filter-name>
15         <url-pattern>/*</url-pattern>
16     </filter-mapping>

--------例2：提交到Servlet，Serlvet再设置为request的attribute，再提交到jsp页面--------

AttributeSetterServlet.java

 1 public class AttributeSetterServlet extends HttpServlet {
 2     /**
 3      * Generated serialVersionUID
 4      */
 5     private static final long serialVersionUID = 8458482445490259121L;
 6 
 7     @Override
 8     public void doGet(HttpServletRequest req, HttpServletResponse resp)
 9             throws ServletException, IOException {
10         // 在这里也没有调用request.setCharacterEncoding()，
11         // 你把CharacterEncodingFilter关闭了试试，看看结果有什么
12         // 不一样
13         String attr = req.getParameter("attr");
14         if (attr != null) {
15             // System.out.println(this + ", " + attr); // @Debug
16             attr += " -- 这是一个小尾巴";
17             req.setAttribute("attr", attr);
18             req.getRequestDispatcher("display_attribute.jsp").forward(req, resp);
19         }
20     }
21     @Override
22     public void doPost(HttpServletRequest req, HttpServletResponse resp)
23             throws ServletException, IOException {
24         this.doGet(req, resp);
25     }
26 }

input_attribute.html

 1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 2 <html>
 3 <head>
 4 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 5 <title>Insert title here</title>
 6 </head>
 7 <body>
 8     <form action="AttributeSetterServlet" method="post">
 9         <!-- 输入中文来测试 -->
10         请输入要设置的attribute：<input type="text" name="attr">
11         <input type="submit" value="显示">
12     </form>
13 </body>
14 </html>

display_attribute.jsp

<%@ page language="java" contentType="text/html"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>Insert title here</title>
</head>
<body>
    <h1>设置的attribute是：<%=request.getAttribute("attr")%></h1>
</body>
</html>

web.xml中添加如下代码：

 1     <servlet>
 2         <servlet-name>attribute-setter-servlet</servlet-name>
 3         <servlet-class>
 4             org.foo.servletdemo.AttributeSetterServlet
 5         </servlet-class>
 6     </servlet>
 7     <servlet-mapping>
 8         <servlet-name>attribute-setter-servlet</servlet-name>
 9         <url-pattern>/AttributeSetterServlet</url-pattern>
10     </servlet-mapping>