The following persistence properties will connect to AppEngine

datanucleus.ConnectionURL=appengine

So you create your PersistenceManagerFactory or EntityManagerFactory with these properties. Thereafter you have the full power of the JDO or JPA APIs at your disposal, for your Google BigTable datastore.

Whilst stating that DataNucleus supports Google AppEngine we also need to point out the following to answer some comments made about GAE/J and DataNucleus.

• DataNucleus is an independent project and provides complete JDO/JPA implementations for RDBMS, as well as quite complete implementations for ODBMS, XML, Excel, ODF, HBase, JSON, Amazon S3, LDAP etc. DataNucleus did not provide the plugin for BigTable, though we did offer help in creating it
• Limitations of GAE/J's DataNucleus plugin (provided by Google) are limitations in that and in the BigTable datastore. They are not limitations in DataNucleus, nor are they limitations in the JDO/JPA specifications
• GAE/J's DataNucleus plugin supports some non-standard JDO query syntax. This is against the JDO spec and has been raised with them.
• GAE/J's documentation for JDO implies that each field needs to be marked @Persistent. This is wrong and misleading and has also been raised with them. The definitive documentation for JDO is in the JDO spec and the DataNucleus documentation, nowhere else
• GAE/J's DataNucleus plugin will be extended in the future to remove some of the obvious limitations
• GAE/J's DataNucleus plugin could easily be changed to take advantage of DataNucleus provided in-memory query evaluation and this would alleviate many concerns of users about missing query constructs. Code to do this was contributed to Google but is not included in their plugin yet

Google AppEngine (TM) for Java provides developers with a simple environment in which to develop and deploy web based applications. There have been many blogs about this in recent days. Below are some

• GWT and JDO on the Java App Engine
• 1st look at App Engine using JDO persistence capable classes over GWT RPC
• Google AppEngine for java, first impressions
• Google AppEngine Java Test Ride
• Google App Engine adds Java support (Review)
• Googles Groovy AppEngine
• Google AppEngine for Java with Rich Ruby clients
• Google AppEngine limitations for Java (and how to overcome them)
• Google AppEngine and GWT now a marriage made in heaven
• Re-thinking Object-Relational Mapping in a Distributed Key-Store world
• Migration to Google AppEngine

If you find others and think others would benefit from them please notify us via the forum