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samzw
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程序出错:java.lang.NullPointerException
程序如下:
package test;
import java.sql.*;
public class DBCon
{
String sDBDriver="com.microsoft.jdbc.sqlserver.SQLServerDriver";
//需要你加载sql server的包
String sConnStr="jdbc:microsoft:sqlserver://127.0.0.1:1433;databaseName=Northwind";
private Connection conn=null;
private ResultSet rs=null;
private Statement stmt=null;
public void DBCon()
{
try
{
Class.forName(sDBDriver);
}
catch(java.lang.ClassNotFoundException e)
{
System.out.println("DBcon():"+e.getMessage());
}
}
public ResultSet executeQuery(String sql)
{
try
{
conn=DriverManager.getConnection(sConnStr,"sa","samzw");
stmt=conn.createStatement();
rs=stmt.executeQuery(sql);
}
catch(SQLException ex)
{
System.out.println("aq.executeQuery:"+ex.getMessage());
}
return rs;
}
public void closeStmt()
{
try
{
stmt.close();
}
catch(SQLException e)
{
e.printStackTrace();
}
}
public void closeConn()
{
try
{
conn.close();
}
catch(SQLException e)
{
e.printStackTrace();
}
}
}
<%@page language="java" import="java.sql.*"%>
<jsp:useBean id="DBConn1" scope="page" class="test.DBCon"/>
<html>
<head>
<title>JSP Test </title>
</head>
<body>
<%
ResultSet RS=DBConn1.executeQuery("select * from guestbook");
if (RS==null) out.print("NullPointerException");
while (RS.next())
{
out.print(""+RS.getString("customerid")+"");
out.print(""+RS.getString("companyname")+"");
out.print(""+RS.getString("ContactName")+"");
}
RS.close();
%>
</body>
</html>
程序编译没问题,class路径也没问题(不然,一大堆找不到class的错误),可在IE下提示
java.lang.NullPointerException,请高手指点
程序如下:
package test;
import java.sql.*;
public class DBCon
{
String sDBDriver="com.microsoft.jdbc.sqlserver.SQLServerDriver";
//需要你加载sql server的包
String sConnStr="jdbc:microsoft:sqlserver://127.0.0.1:1433;databaseName=Northwind";
private Connection conn=null;
private ResultSet rs=null;
private Statement stmt=null;
public void DBCon()
{
try
{
Class.forName(sDBDriver);
}
catch(java.lang.ClassNotFoundException e)
{
System.out.println("DBcon():"+e.getMessage());
}
}
public ResultSet executeQuery(String sql)
{
try
{
conn=DriverManager.getConnection(sConnStr,"sa","samzw");
stmt=conn.createStatement();
rs=stmt.executeQuery(sql);
}
catch(SQLException ex)
{
System.out.println("aq.executeQuery:"+ex.getMessage());
}
return rs;
}
public void closeStmt()
{
try
{
stmt.close();
}
catch(SQLException e)
{
e.printStackTrace();
}
}
public void closeConn()
{
try
{
conn.close();
}
catch(SQLException e)
{
e.printStackTrace();
}
}
}
<%@page language="java" import="java.sql.*"%>
<jsp:useBean id="DBConn1" scope="page" class="test.DBCon"/>
<html>
<head>
<title>JSP Test </title>
</head>
<body>
<%
ResultSet RS=DBConn1.executeQuery("select * from guestbook");
if (RS==null) out.print("NullPointerException");
while (RS.next())
{
out.print(""+RS.getString("customerid")+"");
out.print(""+RS.getString("companyname")+"");
out.print(""+RS.getString("ContactName")+"");
}
RS.close();
%>
</body>
</html>
程序编译没问题,class路径也没问题(不然,一大堆找不到class的错误),可在IE下提示
java.lang.NullPointerException,请高手指点