Hi, I'm new in JDO, so I think this problem may sounds stupid...
I'm working on my application on App-engine, and feel really confused
about how to use the PersistenceManager in my app...
1) At the very beginning I tried to maintain only one static pm
instance in my app, but I found that when I try to update the entities
in datastore, it does not write back, since I do not close the pm.
2) Then, I tried to get a new pm in every request, and after the
request I close it. But I still store the pm as a static field in a
DaoBase class. the code looks like:
PersistenceManager pm = PFM.get().getPersistenceManager();
DaoBase.setPm(pm);
....do the request...
DaoBase.getPm().close();
DaoBase.setPm(null);
But when multiple requests come concurrently, things becomes messy and
sometimes the DaoBase.getPm() will returns null during a request.
3) Use new pm each time when reading the datastore, then detach the
object from pm, close the pm. Then during update time, use a new pm to
update it. But the problem here is when there is some owned
relationship between datastore entities, a detatched object will not
fetch the data automatically, like:
/////////////////////////////
class Address {
....
}
class Employee {
private List<Address> addressList;
public List<Address> getAddressList() {
return addressList;
}
}
///////////////////////////////
the getAddressList() will always return null.
So...What is the right way to use PersistenceManager?
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