File APIs for Java Developers
Manipulate DOC, XLS, PPT, PDF and many others from your application.
The moose likes Object Relational Mapping and the fly likes 2 Questions regarding JDO Big Moose Saloon
  Search | Java FAQ | Recent Topics | Flagged Topics | Hot Topics | Zero Replies
Register / Login

Win a copy of Java Interview Guide this week in the Jobs Discussion forum!
JavaRanch » Java Forums » Databases » Object Relational Mapping
Bookmark "2 Questions regarding JDO" Watch "2 Questions regarding JDO" New topic

2 Questions regarding JDO

sopal Pal
Ranch Hand

Joined: Aug 04, 2003
Posts: 83
Q1 : I was going through the article JDO Vs CMP located at

What does the author mean when he says

- "JDO does not support managed relationships, although some vendors offer them as optional features"

I am confused what does managed relationships mean here.
Does it imply that Cascade Delete(s) etc. are not taken care of in JDO

Q2. My next question is with reference to the Caching Model in JDO.

Assuming that the Client and JDO Implementations are running on the same JVM, if JDO caches all of the query data - would not the JVM run out of memory after some time.

Where are the caching times etc conffigured.

If the Client is a GUI Intensive applications that needs to maintain the queried data in its own structures would not it result in a memory hungry JVM


Erik Bengtson
Ranch Hand

Joined: Dec 06, 2003
Posts: 90
answer 1:

jdo 2 introduces dependent objects which permits you to cascade delete your objects

answer 2:

the default jdo cache is weak reference type which means in general terms if you get out of memory the cache will be gargabe collected
Erik Bengtson
Ranch Hand

Joined: Dec 06, 2003
Posts: 90
I forgot to say, JPOX supports managed relationships
I agree. Here's the link:
subject: 2 Questions regarding JDO
It's not a secret anymore!