refresh state problem

[Carlos Conti]

Hi there,

I am runnign some maintainance tasks and need to update hierarchy relationships between my entities. The process is successful. However I have to restart the application contianer in order to update the contents in the application. Therefore I am having a refresh problem in my Persistence methods.

Let me post the main two methods I use.

public static synchronized void persist(Object o){

        habilitaEntityManager();

        //guardando el objeto
        entityManager.getTransaction().begin();
        entityManager.merge(o);
        entityManager.flush();
        entityManager.getTransaction().commit();
        entityManager.clear();
        entityManager.close();
    }

public static synchronized void deleteFromDatabase(Object o){
		habilitaEntityManager();
        /*
         *	Metodo 1: No lo puedo usar poruqe no he extendido las clases de manera
         *  que para todas pueda cargar la instancia para luego borrarla, para usar
         *  este metodo necesito extender una superinstancia que contenga el metodo
         *  getId() para poder cargarla en el contexto de persistencia.SOLUCION: Usar
         *  la reflexion de Java para localizar el valor
         */
		Integer i = null;
		try{
			Class c = o.getClass();
			Method m = c.getMethod("getId", new Class[]{});
			i = (Integer) m.invoke(o, new Object[]{});

			entityManager.getTransaction().begin();
	        Object so  = entityManager.merge(o);
	        entityManager.getTransaction().commit();
	        entityManager.getTransaction().begin();
	        entityManager.remove(so);
	        entityManager.getTransaction().commit();
	        entityManager.clear();
	        entityManager.close();

		}catch(Exception exc){
			exc.printStackTrace();
		}



		/*
		 * Metodo 2: sino la cargo en persistencia, debo ejecutar un query para
		 * borrarla (query JPA)
		 *
		 */
		/*
		String className = o.getClass().getName();
		className = className.substring(className.lastIndexOf('.')+1);
		String query = "DELETE FROM " + className + " o WHERE o.id = :id";
		entityManager.getTransaction().begin();
		Query q = entityManager.createQuery(query);
		q.setParameter("id", id);
		q.executeUpdate();
		entityManager.getTransaction().commit();
        entityManager.clear();
        entityManager.close();
        */
	}

public static synchronized List readMethod(String contenidoQuery,Hashtable parameters){
		Object res = null;
		habilitaEntityManager();
		Query q = entityManager.createQuery(contenidoQuery);

		Enumeration en = parameters.keys();
		while(en.hasMoreElements()){
			String pamName = (String) en.nextElement();
			Object pamValue = parameters.get(pamName);
			q.setParameter(pamName, pamValue);
		}

		List l = q.getResultList();
		return l;
	}

May there be something I am missing in the reading method, to get the most fresh version of the instance?

Thanks for your help.

Carlos .

[James Sutherland]

What JPA provider are you using?

How does your maintenance task modify the database, directly or through JPA?
It seems like you are using a shared cache (L2 cache).

You need to either,
- clear / invalidate the cache after running your
- refresh your objects
- disable the shared cache

JPA 2.0 provides cache configuration and API. If using JPA 1.0, you will need to use configuration specific to your JPA provider.

See,
http://en.wikibooks.org/wiki/Java_Persistence/Caching

[Carlos Conti]

Hi James, thanks for your answer.
Let me clarify one point which may have not been clear enough in my first post.
On one side I use EclipseLink1.1 (the contained application, with Tomcat 6.0). The maintenance application is a pure batch task which we let run from time to time to update some pieces of information. On this side I use aswell EclipseLink 1.1 but since running it in my machine in a local copy of the database, I use a different persistenceunit. But both share the same ORM Mapping file. The point is that if I perform a change via the maintenance task, when running the web application at the same time (locally of course), the changes are not noticeable until I restart the web application.

So I use two different persistent units to attack the same db, merely to distinguist the context (RESOURCE_LOCAL vs. JTA). In fact in the server the db runs in the same box as the web application, however I preferred to have things settled from the very beginning.

Many thanks for your post. I will have a close look to the link you provided.

Carlos.