Question

I am using hibernate in my project and it is well going, but my problem is i am little bit confused that is i am going good way for writing hibernate functions. Below i paste my block of code to understand how i had written the hibernate functions please check it and tell me whther it is a correct method. Here is my structure of block code

SessionFactory sessionFactory = 
                (SessionFactory) ServletActionContext.getServletContext().getAttribute(HibernateListener.KEY_NAME);
        Session hibernatesession = sessionFactory.openSession();
        try {
            hibernatesession.beginTransaction();
            // my database access will be here
            hibernatesession.getTransaction().commit();
            hibernatesession.flush();
            }
        catch(Exception e){
          hibernatesession.getTransaction().rollback();
          e.printStackTrace();
        }finally{
          hibernatesession.close();
        }

This is the structure that i have created for all my dao class functions, but now my website is loading very slowly. So my questions is the stricture i have used is a correct one. Is the above code causes to open multiple session hibernate at a time.

Answer 1

It is not good design to do transaction management in a DAO class. I would warmly recommend using Spring and its declarative transaction management, which is a breeze to set up and a no-brainer to use. If that is not available to you, then you should at least make a poor man’s alternative. One suggestion is to make each DAO a subclass of a class that has a method that does the boilerplate part (session open/close, transaction begin/commit) and calls out to an overridable method to do the real work. This would implement the Template pattern for your scenario. This is an outline:

public abstract class DaoTemplate
{
  public void execute() {
    final Session s = ((SessionFactory) ServletActionContext.getServletContext()
        .getAttribute(HibernateListener.KEY_NAME)).openSession();
    try {
      s.beginTransaction();
      doTheRealStuff();
      s.getTransaction().commit();
    }
    catch(Exception e) {
      s.getTransaction().rollback();
      e.printStackTrace();
    } finally { s.close(); }
  }

  protected abstract void doTheRealStuff();
}

Another suggestion, and something I actually used on a project ten years ago, is to implement the Strategy pattern. In that case you’d pass an object to execute that implements the method doTheRealStuff. Also, in that case the DaoTemplate class could be a singleton (a different name for the class would be appropriate then).