java bean 连接ACCESS出现问题 以前可以运行的,现在不行了,出错java.lang.NullPointerException
org.apache.jsp.conndb_jsp._jspService(org.apache.jsp.conndb_jsp:68)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:99)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:325)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:291)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802) 请哪们高手指点一下
package student;
import java.sql.*;
public class conn{
String sDBDriver="sun.jdbc.odbc.JdbcOdbcDriver";
String sConnStr="jdbc:odbc:student";
Connection connect =null;
ResultSet rs =null;
public conn(){
try{
Class.forName(sDBDriver);
}
catch(java.lang.ClassNotFoundException e)
{
System.err.println(e.getMessage());
}
}
public ResultSet executeQuery(String sql)
{
try{
connect=DriverManager.getConnection(sConnStr);
Statement stmt=connect.createStatement();
rs=stmt.executeQuery(sql); }
catch(SQLException ex)
{
System.err.println(ex.getMessage());
}
return rs;
} } <%@ page contentType="text/html; charset=GBK" %>
<%@ page language="java" import="java.sql.*" %>
<jsp:useBean id="connDbBean" scope="page" class="student.conn"/>
<html>
<body>
<table width="500" height="72" border="1" cellpadding="0" cellspacing="0">
<tr>
<td> 姓名</td>
<td>性别</td>
<td>分数</td>
</tr>
<%
ResultSet RS_result=connDbBean.executeQuery("select * from table1");
String studentName="";
String studentSex="";
int studentScore=0;
while(RS_result.next())
{
studentName=RS_result.getString("name");
studentSex=RS_result.getString("sex");
studentScore=RS_result.getInt("score");
%>
<tr>
<td><%= studentName %></td>
<td><%= studentSex %></td>
<td><%= studentScore %></td> </tr>
<%
}
RS_result.close(); %>
</table>
</body>
</html> 以前可以运行的,现在不行了,出错java.lang.NullPointerException
org.apache.jsp.conndb_jsp._jspService(org.apache.jsp.conndb_jsp:68)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:99)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:325)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:291)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802) 请哪们高手指点一下
我测试了一下,是RS_result为NULL
java.lang.NullPointerException错误提示也是说空指针错误啊
可是为什么是空啊
我用JAVA可以连接数据库的
org.apache.jsp.conndb_jsp._jspService(org.apache.jsp.conndb_jsp:68)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:99)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:325)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:291)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802) 请哪们高手指点一下
package student;
import java.sql.*;
public class conn{
String sDBDriver="sun.jdbc.odbc.JdbcOdbcDriver";
String sConnStr="jdbc:odbc:student";
Connection connect =null;
ResultSet rs =null;
public conn(){
try{
Class.forName(sDBDriver);
}
catch(java.lang.ClassNotFoundException e)
{
System.err.println(e.getMessage());
}
}
public ResultSet executeQuery(String sql)
{
try{
connect=DriverManager.getConnection(sConnStr);
Statement stmt=connect.createStatement();
rs=stmt.executeQuery(sql); }
catch(SQLException ex)
{
System.err.println(ex.getMessage());
}
return rs;
} } <%@ page contentType="text/html; charset=GBK" %>
<%@ page language="java" import="java.sql.*" %>
<jsp:useBean id="connDbBean" scope="page" class="student.conn"/>
<html>
<body>
<table width="500" height="72" border="1" cellpadding="0" cellspacing="0">
<tr>
<td> 姓名</td>
<td>性别</td>
<td>分数</td>
</tr>
<%
ResultSet RS_result=connDbBean.executeQuery("select * from table1");
String studentName="";
String studentSex="";
int studentScore=0;
while(RS_result.next())
{
studentName=RS_result.getString("name");
studentSex=RS_result.getString("sex");
studentScore=RS_result.getInt("score");
%>
<tr>
<td><%= studentName %></td>
<td><%= studentSex %></td>
<td><%= studentScore %></td> </tr>
<%
}
RS_result.close(); %>
</table>
</body>
</html> 以前可以运行的,现在不行了,出错java.lang.NullPointerException
org.apache.jsp.conndb_jsp._jspService(org.apache.jsp.conndb_jsp:68)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:99)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:325)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:291)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802) 请哪们高手指点一下
我测试了一下,是RS_result为NULL
java.lang.NullPointerException错误提示也是说空指针错误啊
可是为什么是空啊
我用JAVA可以连接数据库的
stmt就被释放了,而Result变量是存在于stmt上的,stmt没了,Result当然没了。把stmt定义为和Result一样的类属性就可以了。