Generics in EJB 3.0 Result List?

[dhinojosa]

I was just wondering if and when queries will return
"generisized" results from their query? In other words can we expect something like this in the near future?

List result = query.getResultList(Employee.class);

where query of course is a javax.persistence.Query object.

or maybe a

Query q = entityManager.createQuery(Employee.class, "select...");

[dhinojosa]

Sure would help if I use the code tag

List result = query.getResultList(Employee.class);

where query of course is a javax.persistence.Query object.

or maybe a

Query q = entityManager.createQuery(Employee.class, "select...");

[dhinojosa]

DAMMIT! Alright one last time

List<Employee> result = query.getResultList(Employee.class);

Query<Employee> q = entityManager.createQuery(Employee.class, "select...");

[nholbrook]

Why not write your own persistence class that uses a persistence manager?

public interface PersistenceManager
{
EntityManager getEntityManager();

void insert( T entity );

void remove( T entity );

T update( T entity );

T findById( Class entity, Serializable id );

List findAll( Class entity );
}

Now they work with Generics.

[nholbrook]

My findAll uses the template, too but for some reason it was stripped on the post.

[nholbrook]

What a pain in the butt.....

If somebody can tell me how to post a greater than and less than sign on here, I will be glad to post some code. All my template references get removed.

[mazz]

Wrap it in code blocks (left square bracket followed by "code" followed by right square bracket)... there's a button labled "Code" when you are editing a reply - highlight the code and click that button.

List<String> foo = new List<String>;

[nholbrook]

Hey.... It works. How much do you trust the code of a guy who can't figure out how to post on a message board? lol

Anyway, I set this up so we could have a class with standard persistence mechanisms that could be used with different persistent managers. I also like the templating mechanisms.

public interface PersistenceManager
{
 List findByNamedQuery(String queryName, Map<String, Serializable> queryParams);

 EntityManager getEntityManager();

 <T> void insert( T transientInstance );

 <T> void remove( T persistentInstance );

 <T> T update( T detachedInstance );

 <T> T findById( Class<T> transientInstance, Serializable id );

 <T> List<T> findAll( Class<T> transientInstance );
}


------------------------------------------------- Abstract Implementation -----------

public abstract class AbstractPersistenceManagerImpl
 implements PersistenceManager
{
 private static final Log log = LogFactory.getLog(PersistenceManager.class);

 public <T> void insert(T transientInstance)
 {
 log.debug("persisting " + transientInstance.getClass().getName() + " instance");
 try
 {
 getEntityManager().persist(transientInstance);
 log.debug("persist successful");
 }
 catch (RuntimeException re)
 {
 throw new TessRuntimeException(re);
 }
 }

 public <T> void remove(T persistentInstance)
 {
 log.debug("removing " + persistentInstance.getClass().getName() + " instance");
 try
 {
 getEntityManager().remove(persistentInstance);
 log.debug("remove successful");
 }
 catch (RuntimeException re)
 {
 throw new TessRuntimeException(re);
 }
 }

 public <T> T update(T detachedInstance)
 {
 log.debug("merging " + detachedInstance.getClass().getName() + " instance");
 try
 {
 T result = getEntityManager().merge(detachedInstance);
 log.debug("merge successful");
 return result;
 }
 catch (RuntimeException re)
 {
 throw new TessRuntimeException(re);
 }
 }

 public List findByNamedQuery(String queryName, Map<String, Serializable> queryParams)
 {
 log.debug("running named query " + queryName);
 try
 {
 Query query = getEntityManager().createNamedQuery(queryName);
 if (queryParams != null)
 {
 for (String paramName : queryParams.keySet())
 query.setParameter(paramName, queryParams.get(paramName));
 }
 List result = query.getResultList();
 log.debug("merge successful");
 return result;
 }
 catch (RuntimeException re)
 {
 throw new TessRuntimeException(re);
 }
 }

 public <T> T findById(Class<T> transientInstance, Serializable id)
 {
 try
 {
 log.debug("getting " + transientInstance.getClass().getName() + " instance with id: " + id);
 T instance = getEntityManager().find(transientInstance, id);
 log.debug("get successful");
 return instance;
 }
 catch (RuntimeException re)
 {
 throw new TessRuntimeException(re);
 }
 }

 public <T> List<T> findAll(Class<T> transientInstance)
 {
 try
 {
 log.debug("getting all records for " + transientInstance.getClass().getName());
 List<T> instance = getEntityManager().createQuery(
 "from " + transientInstance.getSimpleName()
 + " as instance").getResultList();
 log.debug("get successful");
 return instance;
 }
 catch (RuntimeException re)
 {
 throw new TessRuntimeException(re);
 }
 }

 public abstract EntityManager getEntityManager();
}

------------------------------------ Implementing persistence manager ----------------------------

@Stateless
@Local ({PersistenceManager.class})
public class SecurityPersistenceManagerImpl
 extends AbstractPersistenceManagerImpl
 implements PersistenceManager
{
 @PersistenceContext(unitName="securitymanager")
 EntityManager entityManager;

 @Override
 public EntityManager getEntityManager()
 {
 return entityManager;
 }
}