Basic JPA native query design question

Question

Is this ok to reuse the lookup of the EntityManager and not close it?
//Database call
try {
Query query = Resource.getEntityManager().createNativeQuery(sqlStatement);
results = query.getResultList();
catch(Exception pExc) {
LogTool.error("Error running this query CALENDAR sqlStatement:" + sqlStatement);
public final class Resource {
private static EntityManager entityManager;
public static EntityManager getEntityManager() throws NamingException {
if(entityManager==null) {
Context ctx = new InitialContext();
entityManager = (EntityManager) ctx.lookup(JPA_PERSISTENCE_CONTEXT);
return entityManager;
}

Answer 1

917903 wrote:
Well, it felt silly in every instance to do this same lookup everytime A. so I made the function B.First case
1- It represents a resource to which you shouldn't hold onto.
2- It doesn't represent a resource.
If the first then you should always look it up. If the second it doesn't matter if you look it up every time. So everytime wins for that case.
Second case only applies if there is a measurable and significant performance impact and it does NOT represent a resource (so 2 from above.) If that is the case then hanging onto it makes sense. But I doubt that it would have such an impact.
I wouldn't be surprised that if your JEE container allows you to redefine the pool while the app is running that you would find that choice 1 above is what is going on.