Servlet跳转问题

在下写了两个Servlet，想第一个跳到第二个，但是运行后抛出这样的错误：
type： Exception report
message：
description：The server encountered an internal error () that prevented it from fulfilling this request.
exception：
java.lang.NullPointerException
 ex3_8.UserServlet2.doGet(UserServlet2.java:34)
 ex3_8.UserServlet2.doPost(UserServlet2.java:88)
 javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
 javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
 ex3_8.UserServlet1.doGet(UserServlet1.java:27)
 ex3_8.UserServlet1.doPost(UserServlet1.java:34)
 javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
 javax.servlet.http.HttpServlet.service(HttpServlet.java:802)源代码：
customer.html
<html>
 <head><title>用户详细信息</title></head>
 <body>
  <form method=post action="/ServletModule/userservlet1">
   <h1 align=center>欢迎来到 Shop Stop</h1>
   请您输入用户ID以显示您的详细信息:
   <br>
   <input type=text name=txtuserid>
   <br/>
   <input type=submit value="提交">
  </form>
 </body>
</html>UserServlet1:
package ex3_8;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;public class UserServlet1 extends HttpServlet {
    private static final String CONTENT_TYPE = "text/html; charset=GBK";    //Initialize global variables
    public void init() throws ServletException {
    }    //Process the HTTP Get request
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws
            ServletException, IOException {
        String uid=request.getParameter("txtuserid");
        response.setContentType(CONTENT_TYPE);
        PrintWriter out = response.getWriter();
        ServletContext context=getServletContext();
        context.setAttribute("UserId",uid);
        RequestDispatcher dispatcher=request.getRequestDispatcher("/userservlet2");
        if(dispatcher==null){
                response.sendError(response.SC_NO_CONTENT);
        }
        dispatcher.forward(request,response);
        out.close();
    }    //Process the HTTP Post request
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws
            ServletException, IOException {
        doGet(request, response);
    }    //Clean up resources
    public void destroy() {
    }
}UserServlet2:
package ex3_8;import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import java.sql.*;public class UserServlet2 extends HttpServlet {
    private static final String CONTENT_TYPE = "text/html; charset=GBK";    //Initialize global variables
    public void init() throws ServletException {
    }    //Process the HTTP Get request
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws
            ServletException, IOException {
        String UserPassword=null;
        String FirstName=null;
        String LastName=null;
        String Age=null;
        String Gender=null;
        ServletContext context=getServletContext();
        Object obj=context.getAttribute("userid");
        response.setContentType(CONTENT_TYPE);
        PrintWriter out = response.getWriter();
        out.println("<html>");
        out.println("<head><title>CusterDetails</title></head>");
        try{
            Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
            Connection con=DriverManager.getConnection("jdbc:odbc:petclinicapps","administrator","GSLwenbaihua");
            Statement s=con.createStatement();
            ResultSet rs=s.executeQuery("Select * from CustomerRegistration where UserId'"+obj.toString().trim()+"'");
            boolean flag=rs.next();
            if (flag==true) {
                UserPassword=rs.getString(2);
                FirstName=rs.getString(3);
                LastName=rs.getString(4);
                Gender=rs.getString(5);
                Age=rs.getString(6);
            }else{
                out.println("<font color=red size=7>登录失败</font>");
            }
        }
        catch(java.sql.SQLException sqle){
            out.println("<font color=red size=7>"+sqle.toString()+"</font>");
        }
        catch(ClassNotFoundException e){
            out.println("类未找到异常"+e);
        }
        
        out.println("<body>");
        out.println("<H1 align=center>欢迎来到Shop Stop</H1>");
        out.println("<table width=80% border=0 align=center>");
        out.println("<tr align=center valign=top>");
        out.println("<td colspan=2><h1><em><strong>客户详细信息</strong></em></h1></td>");
        out.println("</tr>");
        out.println("<tr>");
        out.println("<td width=25%><span><strong>用户 ID:</strong></span></td>");
        out.println("<td width=75%><span>"+obj.toString()+"</span></td>");
        out.println("</tr>");
        out.println("<tr>");
        out.println("<td><span><strong>口令:</strong></span></td>");
        out.println("<td><span>"+UserPassword+"</span></td");
        out.println("<tr>");
        out.println("</tr>");
        out.println("<td><span><strong>全名:</strong></span></td>");
        out.println("<td><span>"+FirstName+""+LastName+"</span></td>");
        out.println("</tr>");
        out.println("<tr>");
        out.println("<td><span><strong>性别:</strong></span></td>");
        out.println("<td>"+Gender+"</td>");
        out.println("      </tr>");
        out.println("      <tr>");
        out.println("        <td><span><strong>年龄:</strong></span></td>");
        out.println("        <td>"+Age);
        out.println("        <span>岁</span></td>");
        out.println("</tr>");
        out.println("</table>");
        out.println("</html>");
        out.close();
    }    //Process the HTTP Post request
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws
            ServletException, IOException {
        doGet(request, response);
    }    //Clean up resources
    public void destroy() {
    }
}