请教一个jsp过滤器的问题
我是jsp初学者，我在学习过滤器的时候碰到一些问题，望各位大哥给予帮助。
我做了2个很简单的jsp文件，想通过text文本框提交信息到另外一个页面显示，输入英文字母没有问题，但是输入中文后就出现许多问号，而且不管我在web.xml的init-param里设置参数值为UTF-8还是
gb2312都无法解决，请各位大哥帮忙找找问题究竟出在哪里??
user.jsp的代码：
<%@page contentType= "text/html;charset=gb2312 "%>
<html>
<head> <title> 用户登录 </title> <head>
<body>
<form action= "login.jsp " enctype= "gb2312 ">
<p align= "center ">
姓名 <input type= "text " name= "name " size= "20 ">
<input type= "submit " value= "提交 ">
<input type= "reset " value= "重置 "> </p>
</form>
</body>
</html>
login.jsp的代码：
<%@page contentType= "text/html;charset=gb2312 "%>
<%@page import= "java.util.* "%>
<html>
<body>
你好, <%!String Name;%>
<%
Name=request.getParameter( "name ");
%>
<%=Name%>
今天是
<%
Date today=new Date();
%>
<%=today.getDate()%> 号，星期 <%=today.getDay()%>
<p align= "center ">
<form action= "user1.jsp ">
<input type= "submit " value= "返回 ">
</form> </p>
</body>
</html>
过滤器代码：
package filter;
import java.io.IOException;
import javax.servlet.*;
public class RequestEncodingFilter implements Filter {
protected String encoding = null;
protected FilterConfig filterConfig = null;
protected boolean ignore = true;
protected ServletContext context;
public void init(FilterConfig filterConfig) throws ServletException {
this.filterConfig = filterConfig;
context=filterConfig.getServletContext();
this.encoding = filterConfig.getInitParameter( "encoding ");
String value = filterConfig.getInitParameter( "ignore ");
if (value == null)
this.ignore = true;
else if (value.equalsIgnoreCase( "true "))
this.ignore = true;
else
this.ignore = false;
}
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
if (ignore || (request.getCharacterEncoding() == null)) {
String encoding = selectEncoding(request);
if (encoding != null)
request.setCharacterEncoding(encoding);
}
context.log( "Just for test,don 't worry!! ");
chain.doFilter(request, response);
}
public void destroy() {
this.encoding = null;
this.filterConfig = null;
}
protected String selectEncoding(ServletRequest request) {
return (this.encoding);
}
}
过滤器的class放到了WEB-INF\classes\filter下。
web.xml配置如下：
<?xml version= "1.0 " encoding= "UTF-8 " ?>
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN " "http://java.sun.com/dtd/web-app_2_3.dtd ">
<web-app>
<filter>
<filter-name> RequestEncoding </filter-name>
<filter-class> filter.RequestEncodingFilter </filter-class>
<init-param>
<param-name> encoding </param-name>
<param-value> UTF-8 </param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name> RequestEncoding </filter-name>
<url-pattern> /* </url-pattern>
</filter-mapping>
</web-app>
我为了看过滤器是否起作用，在RequestEncodingFilter里加入了context.log( "Just for test,don 't worry!! ");这样的语句，打开网页测试的时候，看见tomcat的log文件里确实有
Just for test,don 't worry!!这样的语句，说明过滤器确实运行了，但是为什么不起作用呢??
[解决办法]
过滤器的代码改为一下的试一下：
/*
* Copyright 2004 The Apache Software Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License ");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS " BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package filters;
import java.io.IOException;
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.UnavailableException;
/**
* <p> Example filter that sets the character encoding to be used in parsing the
* incoming request, either unconditionally or only if the client did not
* specify a character encoding. Configuration of this filter is based on
* the following initialization parameters: </p>
* <ul>
* <li> <strong> encoding </strong> - The character encoding to be configured
* for this request, either conditionally or unconditionally based on
* the <code> ignore </code> initialization parameter. This parameter
* is required, so there is no default. </li>
* <li> <strong> ignore </strong> - If set to "true ", any character encoding
* specified by the client is ignored, and the value returned by the
* <code> selectEncoding() </code> method is set. If set to "false,
* <code> selectEncoding() </code> is called <strong> only </strong> if the
* client has not already specified an encoding. By default, this
* parameter is set to "true ". </li>
* </ul>
*
* <p> Although this filter can be used unchanged, it is also easy to
* subclass it and make the <code> selectEncoding() </code> method more
* intelligent about what encoding to choose, based on characteristics of
* the incoming request (such as the values of the <code> Accept-Language </code>
* and <code> User-Agent </code> headers, or a value stashed in the current
* user 's session. </p>
*
* @author Craig McClanahan
* @version $Revision: 1.2 $ $Date: 2004/03/18 16:40:33 $
*/
public class SetCharacterEncodingFilter implements Filter {
// ----------------------------------------------------- Instance Variables
/**
* The default character encoding to set for requests that pass through
* this filter.
*/
protected String encoding = null;
/**
* The filter configuration object we are associated with. If this value
* is null, this filter instance is not currently configured.
*/
protected FilterConfig filterConfig = null;
/**
* Should a character encoding specified by the client be ignored?
*/
protected boolean ignore = true;
// --------------------- Public Methods
/**
* Take this filter out of service.
*/
public void destroy() {
this.encoding = null;
this.filterConfig = null;
}
/**
* Select and set (if specified) the character encoding to be used to
* interpret request parameters for this request.
*
* @param request The servlet request we are processing
* @param result The servlet response we are creating
* @param chain The filter chain we are processing
*
* @exception IOException if an input/output error occurs
* @exception ServletException if a servlet error occurs
*/
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain)
throws IOException, ServletException {
// Conditionally select and set the character encoding to be used
if (ignore || (request.getCharacterEncoding() == null)) {
String encoding = selectEncoding(request);
if (encoding != null)
request.setCharacterEncoding(encoding);
}
// Pass control on to the next filter
chain.doFilter(request, response);
}
/**
* Place this filter into service.
*
* @param filterConfig The filter configuration object
*/
public void init(FilterConfig filterConfig) throws ServletException {
this.filterConfig = filterConfig;
this.encoding = filterConfig.getInitParameter( "encoding ");
String value = filterConfig.getInitParameter( "ignore ");
if (value == null)
this.ignore = true;
else if (value.equalsIgnoreCase( "true "))
this.ignore = true;
else if (value.equalsIgnoreCase( "yes "))
this.ignore = true;
else
this.ignore = false;
}
// ------------------------------------------------------ Protected Methods
/**
* Select an appropriate character encoding to be used, based on the
* characteristics of the current request and/or filter initialization
* parameters. If no character encoding should be set, return
* <code> null </code> .
* <p>
* The default implementation unconditionally returns the value configured
* by the <strong> encoding </strong> initialization parameter for this
* filter.
*
* @param request The servlet request we are processing
*/
protected String selectEncoding(ServletRequest request) {
return (this.encoding);
}
}
[解决办法]
web.xml中,过滤器这样配:
<filter>
<filter-name> RequestEncoding </filter-name>
<filter-class> filter.RequestEncodingFilter </filter-class>
</filter>
<filter-mapping>
<filter-name> RequestEncoding </filter-name>
<url-pattern> /* </url-pattern>
</filter-mapping>
其余的去掉
真正的过滤不是在web.xml中实现的 ,是要经过你的这个filter.RequestEncodingFilter类来实现的,在你的类中把所有的字符都过滤成你所需要的类型