GreetingServlet.java 源代码如下：
package servlets;

import java.io.*;
import java.util.*;
import java.sql.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class GreetingServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
        response.setBufferSize(8192);
        //response.setContentType("text/html;charset=GB2312");
        PrintWriter out = response.getWriter();

        // then write the data of the response
        out.println("<html>" + "<head><title>Hello</title></head>");

        // then write the data of the response
        out.println("<body  bgcolor=\"#ffffff\">" +
            "<h2>Hello, my name is Duke. What is yours?</h2>" +
            "<form method=\"get\">" +
            "<input type=\"text\" name=\"username\" size=\"25\">" + "<p></p>" +
            "<input type=\"submit\" value=\"Submit\">" +
            "<input type=\"reset\" value=\"Reset\">" + "</form>");
        String username = request.getParameter("username");

        if ((username != null) && (username.length() > 0)) {
            RequestDispatcher dispatcher =
                getServletContext()
                    .getRequestDispatcher("/response");

            if (dispatcher != null) {
                dispatcher.include(request, response);
            }
        }

        out.println("</body></html>");
        out.close();
    }

    public String getServletInfo() {
        return "The Hello servlet says hello.";
    }
}
ResponseServlet.java 源代码如下：
package servlets;

import java.io.*;
import java.util.*;
import java.sql.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class ResponseServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
        //response.setContentType("text/html;charset=GB2312");
        PrintWriter out = response.getWriter();
        // then write the data of the response
         String username = request.getParameter("username");
        //String username=new String(request.getParameter("username").getBytes("ISO-8859-1"),"GB2312");
        if ((username != null) && (username.length() > 0)) {
            String s=request.getParameter("username");
            byte a[]=s.getBytes("UTF8");
            username=new String(a);
            out.println("<h2>Hello, " + username + "!</h2>");
        }
    }

    public String getServletInfo() {
        return "The Response servlet says hello.";
    }
}
过滤器：SetCharacterEncodingFilter.java 源代码如下：
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.http.*;

public class SetCharacterEncodingFilter implements Filter {

    protected String encoding = null;

    protected FilterConfig filterConfig = null;

    protected boolean ignore = true;

    public void destroy() {

        this.encoding = null;
        this.filterConfig = null;

    }

    public void doFilter(ServletRequest request, ServletResponse response,
                         FilterChain chain)
    throws IOException, ServletException {

        // Conditionally select and set the character encoding to be used
        if (request.getCharacterEncoding() == null) {
            if (this.encoding != null){
                request.setCharacterEncoding(encoding);
                ((HttpServletResponse) response).setContentType("text/html; charset=" + encoding);
            }
        }


    // 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");
        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 String selectEncoding(ServletRequest request) {

        return (this.encoding);

    }


}
web.xml文件如下：
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/j2ee" version="2.4" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
  <display-name>hello2</display-name>
  <filter>
  <filter-name>SetCharacterEncodingFilter</filter-name>
  <filter-class>filters.SetCharacterEncodingFilter</filter-class>
  <init-param>
  <param-name>encoding</param-name>
  <param-value>gb2312</param-value>
  </init-param>
  </filter>
 
  <servlet>
    <display-name>GreetingServlet</display-name>
    <servlet-name>GreetingServlet</servlet-name>
    <servlet-class>servlets.GreetingServlet</servlet-class>
  </servlet>
  <servlet>
    <display-name>ResponseServlet</display-name>
    <servlet-name>ResponseServlet</servlet-name>
    <servlet-class>servlets.ResponseServlet</servlet-class>
  </servlet>
  <filter-mapping> 
  <filter-name>SetCharacterEncodingFilter</filter-name> 
  <url-pattern>/*</url-pattern> 
  </filter-mapping> 
  <servlet-mapping>
    <servlet-name>GreetingServlet</servlet-name>
    <url-pattern>/greeting</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
    <servlet-name>ResponseServlet</servlet-name>
    <url-pattern>/response</url-pattern>
  </servlet-mapping>
</web-app>
问题是输入中文，显示为乱码，请各位高手指教，谢谢！