if(rs.next()){报错，貌似是什么空指针的问题

Mhypnos 2015-06-14 06:29:15

这是tomcat显示页面的报错内容
org.apache.jasper.JasperException: An exception occurred processing JSP page /reg2.jsp at line 23

20: String uid=request.getParameter("uid");
21: String sql="select*from student where uid='"+uid+"'";
22: ResultSet rs=db.executeQuery(sql);
23: if(rs.next()){
24: rs.close();
25: %>
26: <p>对不起！你输入的学号有误，请重新填写</p>

Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:521)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:430)
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:723)

root cause
java.lang.NullPointerException
org.apache.jsp.reg2_jsp._jspService(reg2_jsp.java:86)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:723)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:388)
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:723)

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caodashen 2015-06-15

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sql文打印出来跑一下目测搜出来没值

yueyakk 2015-06-14

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把数据库查询的代码写在jsp里，，，，，看一下mvc吧，你这个代码看着好乱啊查一下uid是否获取到了，还有你的select*from 中间没有空格吗？

Mhypnos 2015-06-14

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这是java的代码 package opendb; import java.sql.*; public class opendb { String sDBDriver="sun.jdbc.odbc.JdbcOdbcDriver"; String sConnStr="jdbc:odbc:JSP"; Connection conn=null; ResultSet rs=null; public opendb() { try{ Class.forName(sDBDriver);} catch(java.lang.ClassNotFoundException e){ System.err.println("opendb(): "+ e.getMessage());} } public ResultSet executeQuery(String sql) { rs=null; try { conn=DriverManager.getConnection(sConnStr,"sa",""); Statement stmt=conn.createStatement(); rs=stmt.executeQuery(sql); } catch(SQLException ex){ System.err.println("aq.executeQuery: " + ex.getMessage());} return rs; } } 这是jsp的代码 <%@ page language="java" import="java.sql.*" pageEncoding="GBK"%> <SCRIPT language=JavaScript> function backward() { history.back(); } </SCRIPT> <html> <head> <title>请核对一下信息</title> <meta http-equiv="Content-Type"content="text/html;charset=GBK"> </head> <style type="text/css">  </style> <body bgcolor="#FFFFFF"text="#000000"> <%@ page language="java"import="java.sql.*"%> <jsp:useBean id="db"scope="page"class="opendb.opendb"/> <% String uid=request.getParameter("uid"); String sql="select*from student where uid='"+uid+"'"; ResultSet rs=db.executeQuery(sql); if(rs.next()) {rs.close(); %> <p>对不起！你输入的学号有误，请重新填写</p> <p><input type="button" name="Button2" value="返回上一步" onClick="backward()"></p> <%} else{ rs.close(); String IDnumber=request.getParameter("IDnumber"); byte[] tmpbyte=IDnumber.getBytes("ISO8859_1"); IDnumber=new String(tmpbyte); String gender=request.getParameter("gender"); tmpbyte=gender.getBytes("ISO8859_1");