package webdemo1;

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

public class MyServlet extends HttpServlet {

    private static final String CONTENT_TYPE = "text/html; charset=GBK";

    //初始化全局变量
    public void init() throws ServletException {
    }

    //处理 HTTP 请求
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws
            ServletException, IOException {
        response.setContentType(CONTENT_TYPE);
        response.setCharacterEncoding("GB2312");
        PrintWriter out = response.getWriter();
        try{
            String userName = request.getParameter("username");
            String Password = request.getParameter("password");
            if(userName.equals(" ")||Password.equals(" "))
            {
                 userInterface(response);
            }
            else
            {
                out.println("<b>" + userName +"</b> 欢迎第一次使用Servlet <br/>");
                out.println("<b>今天的日期是:</b>" + new Date());
            }
        }
        catch(Exception e){
            userInterface(response);
        }
        out.close();
    }

    public void userInterface(HttpServletResponse response)throws
           IOException{
       PrintWriter out = response.getWriter();
       out.println("<html>");
       out.println("<head><title>欢迎使用Servlet!</title></head>");
       out.println("<body bgcolor =  \" #ffffff \">");
       out.println("<h1 align = center>欢迎第一次使用Servlet</h1>");
       out.println("<form method=post action=/WebModule1/MyServlet>");
       out.println("<br/>");
       out.println("用户名:<input type='text' name='username'><br/>");
       out.println("密码:<input type='password' name='password'><br/>");
       out.println("<input type=submit value='提交'><br/>");
       out.println("</form>");
       out.println("</body>");
       out.println("</html>");
   }

    //处理 HTTP Post 请求
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws
            ServletException, IOException {
        doGet(request, response);
    }

    //清除资源
    public void destroy() {
    }

    private void jbInit() throws Exception {
    }

}

应该是填完登陆页面显示用户名，为什么总是出错？望高手指教！！不胜感激！！