Question

求大神帮忙解决错误 做JSP浏览器访问时出现如下错误，但是我怎么觉得代码没错呢 说是12行有问题

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: An exception occurred processing JSP page /JSP/testMySQL1.jsp at line 12
9: <jsp:useBean id="DBconn1" scope="page" class="myBean.DBconn" />
10: <%
11: ResultSet RS=DBconn1.executeQuery("select * from test");
12: while (RS.next())
13: {
14: out.print("<LI>"+RS.getString("test1")+"</LI>");
15: out.print("<LI>"+RS.getString("test2")+"</LI>");

Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:519)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:428)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

root cause
java.lang.NullPointerException
org.apache.jsp.JSP.testMySQL1_jsp._jspService(testMySQL1_jsp.java:75)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:386)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

note The full stack trace of the root cause is available in the Apache Tomcat/6.0.32 logs.
--------------------------------------------------------------------------------
Apache Tomcat/6.0.32
以下是java源代码文件
package myBean;
import java.sql.*;
public class DBconn
{
String DBDriver="com.mysql.jdbc.Driver" ;
String url="jdbc:mysql://localhost:3306/pubs" ;
String user="root";
String password="5201314284";
Connection conn=null;
ResultSet rs=null;
public DBconn()
{
try
{
Class.forName(DBDriver);
//加载数据库驱动程序
}
catch(java.lang.ClassNotFoundException e)
{
System.err.println("DBconn():"+e.getMessage());
}
}
public ResultSet executeQuery(String sql)
{
rs=null;
try
{
conn=DriverManager.getConnection(url,user,password);
//与DBMS建立连接
Statement stmt=conn.createStatement();
rs=stmt.executeQuery(sql);
}
catch(SQLException ex)
{
System.err.println("aq.executeQuery:"+ex.getMessage());
}
return rs;
}
}

Answer 1

楼主你到executeQuery这个方法内部看看资源有没有打开，或者是不是关闭了连接，楼主你看看

追问

连接正常 executeQuery不知道知道怎么使用

Answer 2

空指针错误！！你先去数据库确认下看看那条语句是不是能查出数据来！！

追问

select * from test是能够查询出来东西的 我也不知道为什么

Answer 3

建议楼主贴上你的DBconn1那部分的代码，这样才好找原因

追问

亲 文件已经上传了 希望您能继续帮我回答，解答疑问，谢谢

追答

你的程序我试了一遍，在我的电脑上是可以运行出正确结果的，DBconn那部分代码没有问题，那应该是出在JSP页面上了。我把自己试的JSP代码贴上来，你对比一下，看问题出在哪里。你参考一下。

My JSP 'My.jsp' starting page

"+RS.getString("idstudent")+"");
out.print(""+RS.getString("mingzi")+"");
}
%>