JavaBean Connect to Database, Which should return?

[xie yufei]

Commonly, we use JavaBean to connect to database in Jsp, What should return to the Jsp? Some one say the "ResultSet", and others say use ArrayList, I am confused. The examples:
1、return ResultSet

public class DbBean { ��
public ResultSet execSQL(String sql) throws SQLException{ 
                    Statement s = dbCon.createStatement(); 
                    ResultSet r = s.executeQuery(sql); 
                    return (r == null) ? null : r; 
                    } ��
}
    

2、return ArraList

public class DbBean { ��
    public List getUsers() { 
        ResultSet rs = userDbQuery();
        List retval = new ArrayList();
        while (rs.next()) {
           retval.add(rs.getString(1));
        }
        return retval;
    }
}
    

[Christophe Verré]

I think that we usually return an ArrayList, BUT:
I don't think that it is a good idea to launch a query for each call.
Usually, we only have

public List getUsers() {
  return users;
} 

where users is a member variable. You should make a DB call only once, before displaying the JSP.

[xie yufei]

where users is a member variable. You should make a DB call only once, before displaying the JSP.

Satou kurinosuke, thanks a lot for your kindness!

[ak pillai]

The best practice is to write your own Data Access Object (DAO class/ look for DAO pattern). Your DAO class is responsible for accessing the data from the database and map the ResultSet to JavaBean(s) and return a Collection (i.e List, Set, Map etc) of JavaBeans or a single JavaBean.

Note: If you have heard of a O-R(Object to Relational mapping) framework called Hibernate that is what it does. Still you need to use a DAO.

[xie yufei]

Arulkumaran Kumaraswamipillai, thank you very much!

Though what you say is difficult for me, I still can learn more fresh knowlege from you words.