Re: [castor-dev] Multiple JDO objects with different mapping files

[Patrick van Kann]

Castor uses a caching mechanism that would probably account for the 
behaviour you are experiencing. The cache of the first JDO is invisible 
to the second, and vice-verse. When you use the db.load() method, the 
object will be loaded from the cache if it has been previous loaded. If 
you use an OQL query, then the cache is not used.

It is possible to set cache-type to "none" in the mapping, though this 
may not solve all of your problems if you have a high degree of 
concurrency. If the 2 JDO objects are both trying to update rows in the 
database simultaneously, you may get errors associated with the 
detection of dirty reads/writes.

I hope this helps.

Patrick

HAMMELL,THOMAS (HP-NewJersey,ex2) wrote:

I'm trying to use multiple JDO objects to access the same database in 
different ways.  I have a database that I'm using to represent 
directories and files in a file system.  I have two tables a directory 
table and a file table. In some operations when I load a directory I 
want to load all the corresponding files that are children of the 
directory. For other operations when I load a directory I don't want 
to load the corresponding files.  To do this I created two mapping 
files one that specifies the relation between the directories and 
files and one that doesn't.  I then created two JDO objects one 
corresponding to each mapping file.  The problem is that both JDO 
objects give the same results when I retrieve a directory.  For 
example I first create the JDO object which corresponds to the mapping 
file that defines a relation between the directories and files then I 
create the JDO object that corresponds to the mapping file that 
doesn't have a relationship between directories and files.  If I use 
the second JDO object to retrieve a directory I get its corresponding 
files for some reason even though the second JDO object doesn't know 
the relationship between directories and files.  If I create the JDO 
objects in the opposite order then I get the opposite behavior.  It 
almost seems that there is some kind of caches that is happening that 
is preventing the second JDO object from being created correctly.  Is 
this a know problem and if so how do I get around it. If it is not a 
know problem then I would like to add it to the bug list.  If I did 
not explain the problem properly and you need more explanation let me 
know. I have a complete example that shows the problem.
 
 
    Thanks
        Tom
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