javabean与jsp的传值
我写了类,在类内或类间调用一个函数有返回直,但在jsp中调用同一个函数就返回空直  
这是什么原因啊,怎么解决,谢谢  
package   sqlBean;  
import   java.sql.*;  
public   class   topicBean{  
Connection   con=null;  
ResultSet   rs   =   null;  
public   topicBean()   throws   InstantiationException,   IllegalAccessException,   ClassNotFoundException,   SQLException{  
try  
{  
Class.forName( "sun.jdbc.odbc.JdbcOdbcDriver ");  
}   catch   (ClassNotFoundException   e)  
{  
System.out.println(e.toString());  
}  
}  

public   ResultSet   getResult(String   sql){  
rs   =   null;  
try   {  
con   =   DriverManager.getConnection( "jdbc:odbc:web ");  
Statement   stmt   =   con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);  
rs   =stmt.executeQuery(sql);  
}   catch   (SQLException   e)   {  
e.printStackTrace();  
}  
return   rs;  
}  
/*   public   static   void   main(String   at[])   throws   SQLException,   InstantiationException,   IllegalAccessException,   ClassNotFoundException{  
topicBean   cdb   =   new   topicBean();  
ResultSet   rs   =   cdb.getResult( "select   *   from   topic ");  

try   {  
while(rs.next()){  
System.out.println(cdb.rs.getString( "topic_name ")+ " ");  
}  
}   catch   (SQLException   e)   {  
System.out.println( "2 ");  
e.printStackTrace();  
}  
}   */  
}  
jsp中的调用：  
String   sql   =   "select   *   from   topic ";  
ResultSet   rs   =   topicbean.getResult(sql);  
rs   在页面中有NullPointerException  

<jsp:useBean   id= "topicbean "   scope= "session "   class= "sqlBean.topicBean "   />  
topicbean的申明


------解决方案--------------------
。。 没看出来。。
------解决方案--------------------
好呀，我试，你把这“ResultSet rs = topicbean.getResult(sql); ”改为ResultSet rs = request.topicbean.getResult(sql); 看一下行不？不然就把“ <jsp:useBean id= "topicbean " scope= "session " class= "sqlBean.topicBean " /> ”改为 <jsp:useBean id= "topicbean " scope= "request " class= "sqlBean.topicBean " /> 看看。