Servlet.service() for servlet action threw exception出错！！！！ 急喔

Question

*/
public ActionForward execute(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response) {
DynaValidatorForm loginForm = (DynaValidatorForm) form;// TODO Auto-generated method stub
String username=loginForm.getString("userName");
String password=loginForm.getString("password");
if(request.getAttribute("rand").equals(loginForm.getString("rand"))&&userServiceImp.isUser(username, password))
{   HttpSession session=request.getSession();
    Users us=userServiceImp.getUsersDAO().findByUName(username);
    
    ApplicationContext context = new FileSystemXmlApplicationContext("C://workspace//bookstore//WebRoot//WEB-INF//applicationContext.xml");
    RandomValus   randomValus=new RandomValus(); 
    MD5 md5=new MD5();
    String code=md5.getMD5Instance().compute(randomValus.getRandomStr()).toUpperCase();
    session.setAttribute("name",username);
    session.setAttribute("code", code);
    MapperIF mapper =(MapperIF)context.getBean("net.sf.dozer.util.mapping.MapperIF");
Users_static users_static= (Users_static) mapper.map(us,Users_static.class);
Vector userslist=new Vector();
userslist.add(users_static);
session.setAttribute("users", userslist);
return mapping.findForward("success");}
else return mapping.findForward("faild");
}
}我的login.jsp
 <h5>登录</h5>
        <form id="form1"  method="post" action="login.do">
          <label>用户名
            <input name="userName" type="text"/>
          <a href="register_step_one.do" target="_blank" class="font00F">注册新用户</a></label>
          <label>密　码
          <input name="password" type="password"/>
          </label>
          <label>验证码
          <input name="rand" size="5" type="text"/>
         <img id="rand_img" src="VerifyCode.jsp"  width="75" height="20" hspace="6" align="absmiddle"/><a href="#" onclick="javascript:document.getElementById('rand_img').src='VerifyCode.jsp?'+Math.random();">刷新图片</a></label>
          
  <div class="btn_box" align="center"><input name="f_pw_sub" value="登录" type="submit"/><input type="reset" name="reset" value="重置"/></div>
           
        </form>
跳转的jsp
<%
java.text.SimpleDateFormat formatter = new java.text.SimpleDateFormat("yyyy-MM-dd HH:mm:ss");java.util.Date currentTime = new java.util.Date();//得到当前系统时间String str_date1 = formatter.format(currentTime); //将日期时间格式化
String str_date2 = currentTime.toString(); //将Date型日期时间转换成字符串形式
%>    
<div id="pass_left">
    <div id="mem_info">
      <h5>&#27426;&#36814;maxinlife<br/> <%=str_date1%> 
<br/></h5>
  <dl>
    
<dd class="headimg"><img src="images/defaultUser.jpg" alt="头像" height="98" width="98"/></dd>
<dd>昵  称：<span>maxin</span></dd>
<dd>生　日：<span>1941年01月01日</span></dd><dd class="email"><br/>邮  箱：<a href="mailto:[email protected]" target="_blank">[email protected]</a></dd>
  </dl>上面都是主要部分的代码 求大人来帮帮忙 做毕业设计 急用

Answer 1

错误提示
type Exception reportmessagedescription The server encountered an internal error () that prevented it from fulfilling this request.exceptionjavax.servlet.ServletException
org.apache.struts.action.RequestProcessor.processException(RequestProcessor.java:523)
org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:421)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:224)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1194)
org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)root causejava.lang.NullPointerException
com.csu.struts.action.LoginAction.execute(LoginAction.java:59)
org.springframework.web.struts.DelegatingActionProxy.execute(DelegatingActionProxy.java:106)
org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:419)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:224)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1194)
org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)note The full stack trace of the root cause is available in the Apache Tomcat/5.5.23 logs.

Answer 2

lz检查：java.lang.NullPointerException
com.csu.struts.action.LoginAction.execute(LoginAction.java:59)

Answer 3

if(request.getAttribute("rand").equals(loginForm.getString("rand"))&&userServiceImp.isUser(username, password))
===>
String rand = request.getAttribute("rand");
if(null != rand && rand.equals(loginForm.getString("rand"))&&userServiceImp.isUser(username, password))
...
request.getAttribute取出来的有可能是null的,调用null.equals当然报错,这是基本常识,还连发两贴来问