问题：为什么在对数据库进行操作时，用第一个IE能操作成功，而再打开第二个IE不能进行操作，但第一个还是可以正常操作。
出现下列错误
HTTP Status 500 ---------------------------------------------
type Exception report
message
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
org.apache.jasper.JasperException
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:372)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
root cause
java.lang.NullPointerException
org.apache.jsp.in_jsp._jspService(in_jsp.java:85)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:94)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:324)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
note The full stack trace of the root cause is available in the Apache Tomcat/5.0.30 logs.
--------------------------------------------
Apache Tomcat/5.0.30
问题：为什么在对数据库进行操作时，用第一个IE能操作成功，而再打开第二个IE不能进行操作，但第一个还是可以正常操作。
小弟才接触JSP，各位多多指点~~,有那些应注意的地方，就直说~~
备注:jsp+mysql 5.0+tomcat 5.0;
架构:jsp+javabean+database;
文件名为：in.jsp
类名为：DBConn.class
类源文件和jsp源文件如下
package huo;
import java.sql.*;
import java.lang.*;
import java.io.*;
import java.util.*;
public class DBConn{
String dbname= "a ";
String dburl= "jdbc:mysql://localhost/ ";
String dbuser= "root ";
String dbpwd= "r ";
Connection con=null;
ResultSet rs=null;
Statement stm=null;
public DBConn(){
try{
Class.forName( "com.mysql.jdbc.Driver ");
}catch(java.lang.ClassNotFoundException e){
System.out.println( "加载驱动失败 ");
}
}//end DBConn
public void ConnDB(String dbname,String dburl,String dbuser,String dbpwd){//数据库名，地址，用户名和密码
this.dburl=dburl+dbname;
this.dbuser=dbuser;
this.dbpwd=dbpwd;
try{
this.con=DriverManager.getConnection(this.dburl,this.dbuser,this.dbpwd);
//this.con=con;
this.stm=con.createStatement();
//this.stm=stm;
}catch(SQLException e){
System.out.println( "数据库连接失败 ");
}
}//end ConnDB
public ResultSet executQuery(String sql){
try{
rs=this.stm.executeQuery(sql);
}
catch(SQLException ex){
//System.err.println(ex.getMessage());
System.out.println( "记录集获取失败 ");
}
return rs;
}//end executquery
public void executUpdate(String sql){
try{
stm.executeUpdate(sql);
}
catch(SQLException ex){
//System.err.println(ex.getMessage());
System.out.println( "更新操作失败 ");
}
//return true;
}//end executupdate
public void CloseDB(){
con=null;
stm=null;
rs=null;
}
}
in.jsp：
<%@ page contentType= "text/html; charset=gb2312 " language= "java " import= "java.sql.* " errorPage= " " %>
<%@ page import= "java.util.* " %>
<%@ page import= "huo.* " %>
<%@ page pageEncoding= "gb2312 "%>
<%request.setCharacterEncoding( "gb2312 ");%>
<jsp:useBean id= "test2 " class= "huo.DBConn "/>
<html>
<head>
<title> 数据测试页面 </title>
<meta http-equiv= "Content-Type " content= "text/html; charset=gb2312 ">
</head>
<body>
<table width= "760 " border= "10 " align= "center " cellpadding= "2 " cellspacing= "2 " >
<tr>
<td> <div align= "center "> id </div> </td>
<td> <div align= "center "> title </div> </td>
</tr>
<%String sql= "select * from a ";
ResultSet rs2=null;
ResultSet rs=null;
String kk=null;
String title=null;
int id;
String tempp= "test ";
String name= "root ";
String pwd= "r ";
String url= "jdbc:mysql://localhost/ ";
String dbname= "a ";
test2.ConnDB(dbname,url,name,pwd);
kk=request.getParameter( "test ");
if (kk.equals(tempp))
{
String temp=request.getParameter( "title ");
temp=new String(temp.getBytes( "gb2312 "), "gb2312 ");
sql= "insert into a values( "+request.getParameter( "id ")+ ", ' "+temp+ " ') ";
test2.executUpdate(sql);
rs=test2.executQuery( "select * from a ");
while (rs.next())
{
id =rs.getInt(1);
title=rs.getString(2);
%>
<tr>
<td> <div align= "center "> <%=id%> </div> </td>
<td> <div align= "center "> <%=title%> </div> </td>
</tr>
<%
}
rs.close();
test2.CloseDB();
}
%>
</table>
<table align= "center " border= "2 ">
<form method= "post " action= "in.jsp " >
<tr>
<td> id : </td>
<td> <input type= "text " name= "id "> </td>
</tr>
<tr>
<td> content: </td>
<td> <textarea name= "title " > </textarea> </td>
</tr>
<tr>
<td> d <input name= "test " type= "hidden " value= "test "> </td>
<td>
<input type= "submit " name= "ok " value= "oksub ">
</td>
</form>
</tr>
</table>
</body>
</html>
[解决办法]
空指针貌似会出在这里：
kk=request.getParameter( "test ");
if (kk.equals(tempp))
你如果在浏览器直接访问这个页面，那肯定会抛异常的。请检查你访问in.jsp的时候，是否有传参数test过来。
[解决办法]
可能就是楼上说得,你的kk是null,并不一定是操作数据库的空指针
我的异常网推荐解决方案：The server encountered an internal error () that prevented it from fulfilling this request.,http://www.myexception.cn/java-web/317.html
