DataNucleus supports persisting/retrieving objects to/from Google App Engine BigTable datastore
(using the datanucleus-appengine
plugin). Simply specify your connection details as follows
datanucleus.ConnectionURL=appengine:
Please note that you should
always use version 2.1+
of this plugin with this release of
DataNucleus.
Versions 1.x of the plugin have major drawbacks resulting in a very poor reflection of JDO/JPA.
Versions 2.0.x of the plugin are for use with DataNucleus v3.0
Once you have specified your connection details you then create your PMF/EMF as normal
and use JDO/JPA as normal. Things to bear in mind with GAE BigTable usage :-
-
Querying can be performed using JDOQL or JPQL. Some query constructs are evaluated in
the datastore, and you can request that any others are handled in-memory.
If you want queries to automatically evaluate unsupported constructs in-memory just set the
persistence property
datanucleus.appengine.query.inMemoryWhenUnsupported
to "true"
-
Relation Mode : by default all relations are
owned
meaning that when related
objects are persisted they are owned by the original object and their "id" contains the
Key of the owner object. You can set
datanucleus.appengine.relationDefault
to
unowned
and make all relations default to unowned, just like all other supported
datastores
Some references that may be of some use
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