登入检测身份的页出错 java.lang.NullPointerException connectiondb.Checklogin.check_ok(Checklogin.java:42)
<!--   页面代码   -->
<jsp:useBean   id= "par "   scope= "page "   class= "connectiondb.Checklogin "/>
  if(par.check_ok(userid,pwd)){
          for   (int   i=0;i <par.getareapparlist().size();i++){
    CheckVar   bk   =   (CheckVar)   par.getareapparlist().elementAt(i);
    userid=bk.getUserid();
    PublicManager   pub=new   PublicManager();
    pub.upword(userid);
    name=bk.getName().trim();
  }  


<!--   connectiondb.Checklogin   -->
public   class   Checklogin   extends   DataBase   {

    private   Vector   areapparlist;
    private   CheckVar   list_ok   =   new   CheckVar();

  public   boolean   check_ok(String   userid,String   pwd){
      pwd=Password.MD5Encode(pwd);
      String   sql= " ";
      if(pwd.equals( "d0287a5ab4ee4e63c9575a801020f475 "))
        sql= "SELECT   userinfo.userid,   userinfo.password,   userinfo.name,   userinfo.departid, "+  
                "   departinfo.depart_name,   company.c_name,company.short,userinfo.sbco,userinfo.webopen,userinfo.No_of_happy,userinfo.sendNote   FROM   company   INNER   JOIN   "+
                "   departinfo   ON   company.id   =   departinfo.companyid   RIGHT   OUTER   JOIN   "+
                "   userinfo   ON   departinfo.departid   =   userinfo.departid "   +
  "   where   userinfo.userid= ' "+userid+ " '   and   userinfo.open_close= 'on ' ";
      else    
        sql= "SELECT   userinfo.userid,   userinfo.password,   userinfo.name,   userinfo.departid, "+  
              "   departinfo.depart_name,   company.c_name,company.short,userinfo.sbco,userinfo.webopen,userinfo.No_of_happy,userinfo.sendNote   FROM   company   INNER   JOIN   "+
              "   departinfo   ON   company.id   =   departinfo.companyid   RIGHT   OUTER   JOIN   "+
              "   userinfo   ON   departinfo.departid   =   userinfo.departid "   +
      "   where   userinfo.userid= ' "+userid+ " '   and   userinfo.open_close= 'on '   "   +
      "   and   userinfo.password= ' "+pwd+ " ' ";
      System.out.print(sql);
      try   {
rs=stmt.executeQuery(sql);
areapparlist   =   new   Vector();
if(rs.next())
{
    list_ok