Accessing objects after closing the PersistenceManager

Question

I have a session bean which returns a collection of objects obtained from a
query. The problem is if I close my PersistenceManager in the session bean
method, I can't access the objects. What will happen if I don't close it?
Won't I have a memory leak? I'm curious if I'm missing something. Here is
my code, I cut out most of it. The println's work fine if I comment out the
pm.close().
public Collection searchFlights(AirportCode from, AirportCode to, Calendar
calendar, int passengers) {
PersistenceManager pm = null;
try {
pm = factory.getPersistenceManager();
c = (Collection) q.executeWithMap(p);
} finally {
pm.close();
Iterator i = c.iterator();
while (i.hasNext()) {
System.out.println("Flight = " + (Flight) i.next());
return c;

Answer 1

Michael-
Firstly, you do not need to obtain and close the PersistenceManager in
each method if you are using a stateful session bean. However, if you
are using a stateless session bean, section 16.1.1 mandates:
At the end of the business method, the PersistenceManager instance
must be closed. This allows the transaction completion code in the
PersistenceManager to free the instance and return it to the
available pool in the PersistenceManagerFactory.
Now, as it happens, we don't pool PersistenceManagers, and I am fairly
sure that it would work fine if you didn't close it, but it is always
good to respect the spec when writing portable code.
I suspect that the problem that you might be seeing is that your session
bean is serializing the Collection to return to the client. Note that
the full closure of serializable fields can wind up being a huge
performance hit (e.g., the entire object graph in the database may be
instantiated). Bear this in mind when your code is serializing a PC.
To get around the problem, you could throw in a quick serialization
right before you close the PM. E.g.:
new ObjectOutputStream (new ByteArrayOutputStream ()).writeObject (c);
This will be a performance hit, but I doubt that it will be any more so
than sending the entire serialized graph over the network.
In article <[email protected]>, Michael wrote:
I have a session bean which returns a collection of objects obtained from a
query. The problem is if I close my PersistenceManager in the session bean
method, I can't access the objects. What will happen if I don't close it?
Won't I have a memory leak? I'm curious if I'm missing something. Here is
my code, I cut out most of it. The println's work fine if I comment out the
pm.close().
public Collection searchFlights(AirportCode from, AirportCode to, Calendar
calendar, int passengers) {
PersistenceManager pm = null;
try {
pm = factory.getPersistenceManager();
c = (Collection) q.executeWithMap(p);
} finally {
pm.close();
Iterator i = c.iterator();
while (i.hasNext()) {
System.out.println("Flight = " + (Flight) i.next());
return c;
Marc Prud'hommeaux [email protected]
SolarMetric Inc. http://www.solarmetric.com