package org.litesoft.servlets;

import javax.servlet.http.*;

public class HttpSessionHelper
{
    public interface Factory
    {
        Object create();
    }

    public static Object get( HttpSession pSession, Factory pFactory, String pAttribute )
    {
        Object zObject = pSession.getAttribute( pAttribute );
        if ( null == zObject )
        {
            // Quazy double check lock should two browser instances w/ the same Session
            // attempt to create the Attribute at the "same" time!
            //noinspection SynchronizationOnLocalVariableOrMethodParameter
            synchronized ( pAttribute )
            {
                if ( null == (zObject = pSession.getAttribute( pAttribute )) )
                {
                    pSession.setAttribute( pAttribute, zObject = pFactory.create() );
                }
            }
        }
        return zObject;
    }
}