急：jsp连javabean

这是出错信息：出错了！
发生了以下的错误： ----------------------------------------------------------------------------------------------------------------------------------------------------------------
getMessage():
null--------------------------------------------------------------------------------
getLocalizedMessage():
null--------------------------------------------------------------------------------
PrintStatckTrace():
java.lang.NullPointerException at graduate.ExecuteBean.addUser(ExecuteBean.java:60) at org.apache.jsp.AddUser_005fDo_jsp._jspService(org.apache.jsp.AddUser_005fDo_jsp:80) at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97) at javax.servlet.http.HttpServlet.service(HttpServlet.java:802) at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:322) at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:291) at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241) at javax.servlet.http.HttpServlet.service(HttpServlet.java:802) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:856) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:744) at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527) at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80) at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684) at java.lang.Thread.run(Thread.java:595)

解决方案 »

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空指针错误，先看看，数据库有没有连上，就是在java类中，直接调用
public void addUser(UserBean user) throws Exception
{
PreparedStatement pstmt=conn.prepareStatement("insert into user (User_Name,User_Pwd) values(?,?)");
pstmt.setString(1,user.getUserName());
pstmt.setString(2,user.getUserPwd());
pstmt.executeUpdate();
}
看看能不能成功
我用的是tomcat5.5.9，只不会有什么影响吧
可能是连上了,但是你可以用一个bean的main函数中,先构造user类,然后调用addUser看看,有没有问题,<jsp:setProperty name="user" property="*" />确保user类的user属性,和你前一页中的表单中的对应的对象名字一样
肯定是graduate.UserBean有错误,你的SET和GET都写全了吗?两个变量你初始化了吗?你看看,
我把代码贴全些~~~还是没找到
JSP:AddUser.jsp
<%@ page contentType="text/html; charset=gb2312" language="java" import="java.sql.*" errorPage="Error.jsp" %>
<%@ page import="graduate.*" %>
<%@ page import="java.io.*" %>
<%@ page import="java.util.*" %><html>
<head>
<title>Untitled Document</title>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
</head>
<body>
<script language="JavaScript">

</script>
<center>
<h1>增加一个新的用户</h1>
<form action="AddUser_Do.jsp" method="post" name="AddUser">
<table border="1" bgcolor="#0099CC">
<tr><td>用户名：<input type="text" name="username" ></td></tr>
<tr><td>密码：<input type="pssword" name="userpwd" ></td></tr>
<tr><td><input type=submit value=提交 onClick="return RgTest()"></td></tr>
</table>
</form>
</center>
</body>
</html>AddUser_Do.jsp
<%@ page contentType="text/html; charset=gb2312" language="java" import="java.sql.*" errorPage="Error.jsp" %>
<%@ page import="graduate.*" %>
<%@ page import="java.io.*" %><html>
<head>
<title>Untitled Document</title>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
</head>
<jsp:useBean id="user" class="graduate.UserBean" scope="page">
<jsp:setProperty name="user" property="*" />
</jsp:useBean>
<jsp:useBean id="execute" class="graduate.ExecuteBean" scope="page"/>
<%
execute.addUser(user);
%>
<body>
<center>
<h1>增加用户成功</h1>
</center>
</body>
</html>
BEAN:
ExecuteBean.java
/*
* 创建日期 2005-5-19
*
* TODO 要更改此生成的文件的模板，请转至
* 窗口－首选项－ Java －代码样式－代码模板
*/
package graduate;import java.sql.*;
import java.util.*;/**
* @author jc
*
* TODO 要更改此生成的类型注释的模板，请转至
* 窗口－首选项－ Java －代码样式－代码模板
*/
//答题系统相关操作
public class ExecuteBean
{
private Connection conn;

//构造方法获得数据库连接
public void ExecuteBean()
{
String ClassForName="sun.jdbc.odbc.JdbcOdbcDriver";
String ServerDB="jdbc:odbc:graduate";
String User="";
String Password="";

try
{
Class.forName(ClassForName);
conn=DriverManager.getConnection(ServerDB,User,Password);
}
catch(Exception e)
{
e.printStackTrace();
}
}

//查看用户
public void ViewUser(String username) throws Exception
{
Statement stmt=conn.createStatement();
ResultSet rs=stmt.executeQuery("select * from user where User_Name='"+username+"'");
Vector vectoruser=new Vector();
if(rs.next())
{
vectoruser.add(rs.getString("User_Id"));
vectoruser.add(rs.getString("User_Name"));
vectoruser.add(rs.getString("User_Pwd"));
vectoruser.add(rs.getString("User_Score"));
}
}

//添加用户
public void addUser(UserBean user) throws Exception
{
PreparedStatement pstmt=conn.prepareStatement("insert into user (User_Name,User_Pwd) values(?,?)");
pstmt.setString(1,user.getUserName());
pstmt.setString(2,user.getUserPwd());
pstmt.executeUpdate();
}

//修改用户
public void modifyUser(UserBean user) throws Exception
{
PreparedStatement pstmt=conn.prepareStatement("update user set User_Name=?,User_Pwd=?");
pstmt.setString(1,user.getUserName());
pstmt.setString(2,user.getUserPwd());
pstmt.executeUpdate();
}

    //删除用户
public void DeleteUser(String username) throws Exception
{
Statement stmt=conn.createStatement();
stmt.execute("delete from user where User_Name='"+username+"'");
}

//查看管理员
public void ViewAdmin(String adminname) throws Exception
{
Statement stmt=conn.createStatement();
ResultSet rs=stmt.executeQuery("select * from admin where Admin_Name='"+adminname+"'");
Vector vectoradmin=new Vector();
if(rs.next())
{
vectoradmin.add(rs.getString("Admin_Id"));
vectoradmin.add(rs.getString("Admin_Name"));
vectoradmin.add(rs.getString("Admin_Pwd"));
}
}

//添加管理员
public void addAdmin(AdminBean admin) throws Exception
{
PreparedStatement pstmt=conn.prepareStatement("insert into admin (Admin_Name,Admin_Pwd) values(?,?)");
pstmt.setString(1,admin.getAdminName());
pstmt.setString(2,admin.getAdminPwd());
pstmt.executeUpdate();
}

//修改管理员
public void modifyAdmin(AdminBean admin) throws Exception
{
PreparedStatement pstmt=conn.prepareStatement("update admin set Admin_id=?,Admin_Name=?,Admin_Pwd=?");
pstmt.setInt(1,admin.getAdminId());
pstmt.setString(2,admin.getAdminName());
pstmt.setString(3,admin.getAdminPwd());
pstmt.executeUpdate();
}

    //删除管理员
public void DeleteAdmin(String adminname) throws Exception
{
Statement stmt=conn.createStatement();
stmt.execute("delete from admin where Admin_Name='"+adminname+"'");
}

//查看题目
public void ViewSubject(int subjectid) throws Exception
{
Statement stmt=conn.createStatement();
ResultSet rs=stmt.executeQuery("select * from subject where Subject_Id='"+subjectid+"'");
Vector vectorsubject=new Vector();
if(rs.next())
{
vectorsubject.add(rs.getString("Subject_Type"));
vectorsubject.add(rs.getString("Subject_Info"));
vectorsubject.add(rs.getString("getSubject_A"));
vectorsubject.add(rs.getString("getSubject_B"));
vectorsubject.add(rs.getString("getSubject_C"));
}
}

//添加题目
public void addSubject(SubjectBean subject) throws Exception
{
PreparedStatement pstmt=conn.prepareStatement("insert into subject (Subject_Type,Subject_Info,Subject_A,Subject_B,Subject_C,Subject_Answer) values(?,?,?,?,?,?)");
pstmt.setString(2,subject.getSubjectType());
pstmt.setString(3,subject.getSubjectInfo());
pstmt.setString(4,subject.getSubjectA());
pstmt.setString(5,subject.getSubjectB());
pstmt.setString(6,subject.getSubjectC());
pstmt.setString(7,subject.getSubjectAnswer());
pstmt.executeUpdate();
}

    //修改题目
public void modifySubject(SubjectBean subject) throws Exception
{
PreparedStatement pstmt=conn.prepareStatement("update subject set Subject_Id=?,Subject_Type=?,Subject_Info=?,Subject_A=?,Subject_B=?,Subject_C=?,Subject_Answer=?");
pstmt.setInt(1,subject.getSubjectId());
pstmt.setString(2,subject.getSubjectType());
pstmt.setString(3,subject.getSubjectInfo());
pstmt.setString(4,subject.getSubjectA());
pstmt.setString(5,subject.getSubjectB());
pstmt.setString(6,subject.getSubjectC());
pstmt.setString(7,subject.getSubjectAnswer());
pstmt.executeUpdate();
}

    //删除题目
public void DeleteSubject(int subjectid) throws Exception
{
Statement stmt=conn.createStatement();
stmt.execute("delete from subject where Subject_Id='"+subjectid+"'");
}
}
UserBean.java
/*
* 创建日期 2005-5-19
*
* TODO 要更改此生成的文件的模板，请转至
* 窗口－首选项－ Java －代码样式－代码模板
*/
package graduate;/**
* @author jc
*
* TODO 要更改此生成的类型注释的模板，请转至
* 窗口－首选项－ Java －代码样式－代码模板
*/
public class UserBean
{
//定义UserBean类的私有数据
private int userid;
private String username;
private String userpwd;
private int userscore;

//UserBean属性设置方法
public void setUserId(int userid)
{
this.userid=userid;
}
public void setUserName(String username)
{
this.username=username;
}
public void setUserPwd(String userpwd)
{
this.userpwd=userpwd;
}
public void setUserScore(int userscore)
{
this.userscore=userscore;
}

//UserBean属性读取方法
public int getUserId()
{
return this.userid;
}
public String getUserName()
{
return this.username;
}
public String getUserPwd()
{
return this.userpwd;
}
public int getUserScore()
{
return this.userscore;
}
}