Java开发网 - 急急急！！还是解决不了登陆的问题！◎！(java.lang.NullPointerException)

Topic: 急急急！！还是解决不了登陆的问题！◎！(java.lang.NullPointerException)

1.急急急！！还是解决不了登陆的问题！◎！(java.lang.NullPointerException)

Posted by: colagong
Posted on: 2003-05-20 13:41

请大家帮帮忙看看：
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<%@page contentType="text/html;gb2312" %>
<%@page import="java.util.*"%>
<%@page import="java.io.*"%>
<%@page import="java.lang.*"%>
<%@page import="java.sql.*"%>

<HTML>
<HEAD>
<TITLE>用户登陆JSP文档</TITLE>
<META NAME="Generator" CONTENT="EditPlus">
<META NAME="Author" CONTENT="">
<META NAME="Keywords" CONTENT="">
<META NAME="Description" CONTENT="">
</HEAD>

<BODY>
<%String username=new String(request.getParameter("username").getBytes("8859_1"));%>
<%String password=new String(request.getParameter("mima").getBytes("8859_1"));%>

<%
Connection myCon;
Statement stmt;
ResultSet myRs;%>

<%try{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
myCon=DriverManager.getConnection("jdbc:odbc:cola01");
stmt=myCon.createStatement();
%>

<%
username="select * from abc where id='"+username+"'";
myRs=stmt.executeQuery(username);
if(myRs.getString("password").compareTo(password)!=0)
{%>
对不起，输入的密码不正确！ 
<%}else{
%>
输入的密码正确！ 
<%
myRs.close();
}
stmt.close();
myCon.close();
}catch(Exception e){
System.out.println(e);
}
%>

</BODY>
</HTML>
用的是j2sdk+tomcat,提示中没有错误和警告，只出现：
java.lang.NullPointerException
 at org.apache.jsp.login1$jsp._jspService(login1$jsp.java:82)
 at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:107)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
 at org.apache.jasper.servlet.JspServlet$JspServletWrapper.service(JspServlet.java:202)
 at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:382)
 at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:474)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
 at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:243)
 at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
 at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
 at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:201)
 at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
 at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
 at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
 at org.apache.catalina.valves.CertificatesValve.invoke(CertificatesValve.java:246)
 at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
 at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
 at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
 at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2344)
 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164)
 at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
 at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:170)
 at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:170)
 at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
 at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:462)
 at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
 at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
 at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:163)
 at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
 at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
 at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
 at org.apache.catalina.connector.http.HttpProcessor.process(HttpProcessor.java:1011)
 at org.apache.catalina.connector.http.HttpProcessor.run(HttpProcessor.java:1106)
 at java.lang.Thread.run(Thread.java:536)
把这句<%@page import="java.lang.*"%>删了还是一样，为什么？？？
谢谢！！！！

2.Re:急急急！！还是解决不了登陆的问题！◎！ [Re: colagong]	Copy to clipboard
Posted by: 九佰 Posted on: 2003-05-20 16:40 request.getParameter("username") request.getParameter("mima") username password myCon stmt myRs 依次检查上面的值，一定有空值的

3.Re:急急急！！还是解决不了登陆的问题！◎！ [Re: 九佰]	Copy to clipboard
Posted by: 极品飞车 Posted on: 2003-05-20 18:26 java.lang.NullPointerException 表明你使用一个没有初始化的对象,它的值是null的.

4.Re:还是解决不了登陆的问题！◎！(java.lang.NullPointerException [Re: colagong]	Copy to clipboard
Posted by: why Posted on: 2003-05-20 22:34 You can check the generated jsp java file at <TOMCAT_HOME>/work/Standalone/localhost/...

5.Re:急急急！！还是解决不了登陆的问题！◎！(java.lang.NullPointerException) [Re: colagong]	Copy to clipboard
Posted by: xuanhai Posted on: 2003-06-05 16:01 username="select * from abc where id='"+username+"'"; myRs=stmt.executeQuery(username); 加myRs.next(); if(myRs.getString("password").compareTo(password)!=0) //错误在myRs.getString(.....)