This one time, at band camp, Bruce Snyder said:
BS>This one time, at band camp, Rowland Watkins said:
BS>
BS>RW>I'm having difficulties with changing the mapping file for different JDO
BS>RW>instances.
BS>RW>
BS>RW>In the Tips & Tricks section on the Castor homepage, there is a mention
BS>RW>of Castor being able to create "partial class views" and map them onto a
BS>RW>table, allowing the programmer to get only some of the data from the
BS>RW>table. I would like to do this as well as getting all the information
BS>RW>using my original class.
BS>RW>
BS>RW>I attempted to do all this in one mapping file, however, I found that
BS>RW>both the partial and complete classes were being loaded, when I only
BS>RW>wanted the partial one.
BS>RW>
BS>RW>I then tried using multiple JDO configurations for each type of object
BS>RW>mapping I had, i.e. one for partial class and another for the complete
BS>RW>one. The problem that I have noted on the mailing list is that the first
BS>RW>loaded configuration is used for *all* subsequent JDO objects.
BS>RW>
BS>RW>Is it not possible to use dynamically configure the JDO at runtime?
BS>
BS>Rowland,
BS>
BS>This can be achieved using the same JDO instance you simply must reload
BS>the correct mapping descriptor. I have accomplished this in the past
BS>using multiple <database> elements in the database descriptor, each one
BS>with a different name and each one holding a different set of <mapping>
BS>elements. For example:
BS>
BS>
BS><!DOCTYPE databases SYSTEM
"/home/bsnyder/src/castor/build/classes/org/exolab/castor/jdo/conf/jdo-conf.dtd">
BS>
BS><database name="wolf1" engine="postgresql" >
BS> <data-source class-name="org.postgresql.jdbc2.optional.PoolingDataSource">
BS> <params server-name="wolf" database-name="demo9" port-number="5432"
user="demo9" password="demo9" />
BS> </data-source>
BS>
BS> <mapping href="mapping1.xml" />
BS> <mapping href="mapping2.xml" />
BS> <mapping href="mapping3.xml" />
BS></database>
BS>
BS><database name="wolf2" engine="postgresql" >
BS> <data-source class-name="org.postgresql.jdbc2.optional.PoolingDataSource">
BS> <params server-name="wolf" database-name="demo9" port-number="5432"
user="demo9" password="demo9" />
BS> </data-source>
BS>
BS> <mapping href="mapping4.xml" />
BS> <mapping href="mapping5.xml" />
BS> <mapping href="mapping6.xml" />
BS></database>
BS>
BS>Then when I need to load a different sent of mapping descriptors,
BS>I simply call (re)set the configuration for the JDO instance:
BS>
BS> public static final String DATABASE_DESC = "database-blah.xml";
BS> ...
BS> String jdoConfUrl = Thread.currentThread().getContextClassLoader().getResource(
DATABASE_DESC ).toString();
BS> ...
BS> _jdo.setConfiguration( jdoConfUrl );
My apologies, the code above is incomplete. Below is the full version:
public static final String DATABASE_DESC1 = "database-blah1.xml";
public static final String DATABASE_DESC2 = "database-blah2.xml";
...
String jdoConfUrl = Thread.currentThread().getContextClassLoader().getResource(
DATABASE_DESC1 ).toString();
...
_jdo.setConfiguration( jdoConfUrl );
_jdo.setName( "wolf1" );
_db = _jdo.getDatabase();
...
// Do some work with this set of mapping descriptors
...
// Now load the other set of mapping descriptors
String jdoConfUrl = Thread.currentThread().getContextClassLoader().getResource(
DATABASE_DESC2 ).toString();
...
_jdo.setConfiguration( jdoConfUrl );
_jdo.setName( "wolf2" );
_db = _jdo.getDatabase();
...
// And you're now using the new set of mapping descriptors
Bruce
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