Help，为什么~~~

我也碰到过类似的问题
出现这样的错误java.lang.NullPointerException 
大虾们说 因为 对空对象进行了操作

解决方案 »

  1.   

    仔细看看前一页的程序，<form>要放在文本框前才能传数，好好看看有没这个问题！
      

  2.   

    =======reg.jsp===========================================
    <%@ page contentType="text/html;charset=gb2312" %>
    <html>
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=gb2312">
    <META HTTP-EQUIV="Pragma" CONTENT="no-cache">
    <META HTTP-EQUIV="Cache-Control" CONTENT="no-cache">
    <META HTTP-EQUIV="Expires" CONTENT="0">
    <title>DongGuan Job Bank</title>
    <link href="css/Style.css" rel="stylesheet" type="text/css">
    <script language="JavaScript">
    <!--
    function isemail (s)
    {
            // Writen by david, we can delete the before code
            if (s.length > 50)
            {
                    window.alert("email地址长度不能超过100位!");
                    return false;
            }         var regu = "^(([0-9a-zA-Z]+)|([0-9a-zA-Z]+[_.0-9a-zA-Z-]*[0-9a-zA-Z]+))@([a-zA-Z0-9-]+[.])+([a-zA-Z]{2}|net|NET|com|COM|gov|GOV|mil|MIL|org|ORG|edu|EDU|int|INT)$"
             var re = new RegExp(regu);
             if (s.search(re) != -1) {
                   return true;
             } else {
                   window.alert ("请输入有效合法的E-mail地址 ！")
                   return false;
             }
    }function isusername (s)
    {
             var regu = "^([a-zA-Z]+[[email protected]]*)$"
             var re = new RegExp(regu);
             if (s.search(re) != -1) {
                   return true;
             } else {
                   window.alert ("请使用规范的会员名！")
                   return false;
             }
    }function Jtrim(str)
    {        var i = 0;
            var len = str.length;
            if ( str == "" ) return( str );
            j = len -1;
            flagbegin = true;
            flagend = true;
            while ( flagbegin == true && i< len)
            {
               if ( str.charAt(i) == " " )
                    {
                      i=i+1;
                      flagbegin=true;
                    }
                    else
                    {
                            flagbegin=false;
                    }
            }        while  (flagend== true && j>=0)
            {
                if (str.charAt(j)==" ")
                    {
                            j=j-1;
                            flagend=true;
                    }
                    else
                    {
                            flagend=false;
                    }
            }        if ( i > j ) return ("")        trimstr = str.substring(i,j+1);
            return trimstr;
    }
    function checkdata() {
            if (Jtrim(document.frmReg.userName.value)=='') {
                    window.alert ("请输入您的会员名 ！")
                    return false;
            }
            if (Jtrim(document.frmReg.userName.value).length<4) {
                    window.alert ("您的会员名需大于3位 ！")
                    return false;
            }
            if (!isusername(document.frmReg.userName.value)){
               return false;
            }        if (Jtrim(document.frmReg.password.value)=='') {
                    window.alert ("请输入您的密码 ！")
                    return false;
            }
            if (Jtrim(document.frmReg.password.value).length<4) {
                    window.alert ("您的密码数必须大于3位 ！")
                    return false;
            }
            if (document.frmReg.passwordAffirm.value=='') {
                    window.alert ("请输入您的重复密码 ！")
                    return false;
            }

            if (document.frmReg.password.value!=document.frmReg.passwordAffirm.value) {
                    window.alert ("您的密码不一致 ！")
                    return false;
            }

    if (document.frmReg.passwordQuestion.value==''){
    window.alert ("请输入你取回密码的问题")
    return false;
    }

    if (document.frmReg.passwordAnswer.value==''){
    window.alert ("请输入你取回密码的答案")
    return false
    }

            if (document.frmReg.email.value=='') {
                    window.alert ("请输入您的E-mail地址 ！")
                    return false;
            }

            if ( !isemail(document.frmReg.email.value) ){
               return false;
    }

            return true;
    }
    function check(){
      if ((document.frmReg.Username.value=="")||(document.frmReg.Password.value=="")){
         window.alert("请输入会员名/密码！");
         return false;
      }
      else
      return true;
    }function MM_openBrWindow(theURL,winName,features) { //v2.0
      window.open(theURL,winName,features);
    }
    //-->
    </script>
    </head><body bgcolor="#336699" leftmargin="0" topmargin="0" marginwidth="0" marginheight="0">
    <%@ include file="head.htm"%>
    <table width="776" height="5" border="0" cellpadding="0" cellspacing="0" bgcolor="#004D66">
      <tr>
        <td></td>
      </tr>
    </table>
    <table width="776" border="0" cellpadding="0" cellspacing="0" bgcolor="#6699FF">
      <tr> 
        <td width="700">&nbsp;Wednesday, April 09, 2003&nbsp;&nbsp;Welcome <font color="#FFFFFF">Guest</font> 
          to DongGuan Job Bank.</td>
        <td width="50" align="right"><a href="#"><img src="images/help.gif" width="38" height="19" border="0"></a>&nbsp;</td>
      </tr>
    </table>
    <table width="776" height="100%" border="0" cellpadding="0" cellspacing="0">
      <tr> 
        <td width="5" valign="top" bgcolor="#FF9900"><table width="100%" height="150" border="0" cellpadding="0" cellspacing="0" bgcolor="#6699FF">
            <tr>
              <td>&nbsp;</td>
            </tr>
          </table>
          <table width="100%" height="150" border="0" cellpadding="0" cellspacing="0" bgcolor="#FFCC00">
            <tr> 
              <td>&nbsp;</td>
            </tr>
          </table></td>
        <td width="175" valign="top" bgcolor="#F9F9F9"> 
          <table width="175" border="0" cellspacing="0" cellpadding="0">
            <tr> 
              <td width="155" height="25" valign="top"><font size="3" face="Arial, Helvetica, sans-serif"><strong><font color="#FF6600"><img src="images/left.gif" width="20" height="25"></font></strong></font></td>
              <td width="20" align="right" valign="top"><img src="images/memberright.gif" width="20" height="25"></td>
            </tr>
            <tr> 
              <td colspan="2"></td>
            </tr>
          </table>
          <table width="90%" border="0" align="center" cellpadding="2" cellspacing="2">
            <tr valign="top"> 
              <td width="18%"><img src="images/036.gif" width="15" height="16"></td>
              <td width="82%">首先，谢谢你注册成为我们的用户，下面的向导会使你更容易明白注册的事项。<br> <br> </td>
            </tr>
            <tr valign="top"> 
              <td><img src="images/036.gif" width="15" height="16"></td>
              <td>用户名中只能接受英文字符、数字和下划线<br> <br> </td>
            </tr>
            <tr valign="top"> 
              <td><img src="images/036.gif" width="15" height="16"></td>
              <td>当你填写完用户名后，可以先检测用户名是否已经存在，如果已经存在，你可以选用另一个用户有名进行注册。<br> <br> </td>
            </tr>
            <tr valign="top">
              <td>&nbsp;</td>
              <td>&nbsp;</td>
            </tr>
          </table> </td>
      

  3.   

    <td width="596" valign="top" bgcolor="#FFFFFF"> <table width="100%" border="0" cellspacing="0" cellpadding="0">
            <tr> 
              <td width="12" align="left" valign="top"><img src="images/top_round_corner.gif" width="12" height="22"></td>
              <td width="257">&nbsp;</td>
              <td width="58" align="right" valign="top"><img src="images/memberright.gif" width="20" height="25"></td>
              <td width="269" bgcolor="#6699FF">&nbsp;</td>
            </tr>
          </table>
          <table width="570" border="0" align="center" cellpadding="0" cellspacing="0">
            <tr>
              <td colspan="3"><font color="#FF6600" size="4" face="黑体, 宋体"><strong>新用户注册</strong></font></td>
            </tr>
            <tr > 
              <td height="4" colspan="3"><table width="100%" height="4" border="0" cellpadding="0" cellspacing="0" background="images/line4px_h.gif">
                  <tr>
        <td></td>
      </tr>
    </table>
    </td>
            </tr>
            <tr> 
              <td width="130" align="right"><img src="images/userRegleft.gif" width="80" height="550"></td>
              <td width="4" background="images/line4px_v.gif"></td>
              <td valign="top">
                <table width="95%" border="0" align="center" cellpadding="2" cellspacing="2">
                  <form name="frmReg" method="post" action="regsave.jsp" onSubmit="return checkdata()" >
                    <tr> 
                      <td height="40">&nbsp;</td>
                      <td height="40">&nbsp;</td>
                      <td height="40">&nbsp;</td>
                    </tr>
                    <tr>
                      <td height="40" align="right">用户类型：</td>
                      <td height="40"><input name="memberType" type="radio" value="person" checked>
                        个人用户<br>
                        <input type="radio" name="memberType" value="company">
                        招聘单位</td>
                      <td height="40">&nbsp;</td>
                    </tr>
                    <tr> 
                      <td width="25%" height="40" align="right">用户名：</td>
                      <td width="37%" height="40"> <input name="userName" type="text" class="input" id="userName" size="15" maxlength="20"></td>
                      <td width="38%" height="40">[<a href="javascript:" ><font color="#3399FF" onclick="MM_openBrWindow('isrepeat.jsp?userName='+frmReg.userName.value,'检测用户名','width=200,height=200')">检查用户名是否存在</font></a>]</td>
                    </tr>
                    <tr> 
                      <td height="40" align="right">密码：</td>
                      <td height="40"> <input name="password" type="password" class="input" id="password" size="15" maxlength="20"></td>
                      <td height="40">密码至少4位,区分大小写</td>
                    </tr>
                    <tr> 
                      <td height="40" align="right">密码确认：</td>
                      <td height="40"> <input name="passwordAffirm" type="password" class="input" id="passwordAffirm" size="15" maxlength="20"></td>
                      <td height="40">&nbsp;</td>
                    </tr>
                    <tr> 
                      <td height="40" align="right">取回密码问题：</td>
                      <td height="40"> <input name="passwordQuestion" type="text" class="input" id="passwordQuestion" size="20" maxlength="30"></td>
                      <td height="40">&nbsp;</td>
                    </tr>
                    <tr> 
                      <td height="40" align="right">取回密码答案：</td>
                      <td height="40"> <input name="passwordAnswer" type="text" class="input" id="passwordAnswer" size="20" maxlength="30"></td>
                      <td height="40">&nbsp;</td>
                    </tr>
                    <tr> 
                      <td height="40" align="right">E-mail:</td>
                      <td height="40"> <input name="email" type="text" class="input" id="email" size="20" maxlength="50"></td>
                      <td height="40">&nbsp;</td>
                    </tr>
                    <tr align="center"> 
                      <td height="40" colspan="3"> <input type="submit" name="Submit" value="提交"> 
                        &nbsp; <input type="reset" name="Submit2" value="重置"></td>
                    </tr>
                  </form>
                </table></td>
            </tr>
          </table>
        </td>
      </tr>
    </table>
    <%@ include file="bottom.htm"%>
    </body>
    </html>
      

  4.   

    ===============inc.jsp==============================<%@ page info="database handler"%>
    <%@ page import="java.io.*"%>
    <%@ page import="java.util.*"%>
    <%@ page import="java.sql.*"%>
    <%@ page import="javax.servlet.*"%>
    <%@ page import="javax.servlet.http.*"%>
    <%@ page import="com.newben.jobbank.*"%>
    <%@ page import="com.newben.jobbank.admin.*"%>
    <%@ page import="com.newben.util.*"%>
    <%@ page import="com.newben.database.*"%>