数据库发生NullPointerException错误
当用下面数据库代码可以insert即送入数据库数据
但当select即掉出数据库数据时发生NullPointerException错误
怎样解决
javabean代码
package mydate;
import java.lang.*;
import java.sql.*;
public class mydb
{
String sDBDriver="sun.jdbc.odbc.JdbcOdbcDriver";
String sConnStr="jdbc:odbc:chat";
Connection conn=null;
Statement stmt=null;
ResultSet rs=null;
public mydb()
{
try
{
Class.forName(sDBDriver);
}
catch(ClassNotFoundException e)
{
System.err.println("mydb:"+e.getMessage());
}
}
public ResultSet executeQuery(String sql)
{
try
{
conn=DriverManager.getConnection(sConnStr);
stmt=conn.createStatement();
rs=stmt.executeQuery(sql);
}
catch(SQLException ex)
{
System.err.println("aq.executeQuery:"+ex.getMessage());
}
return rs;
}
public void executeUpdate(String sql)
{
try
{
conn=DriverManager.getConnection(sConnStr);
stmt=conn.createStatement();
stmt.executeUpdate(sql);
}
catch(SQLException ex)
{
System.err.println("aq.executeUpdate:"+ex.getMessage());
}
}
}