Monday, March 22, 2010

Warning in JDO lazy fetch with App Engine

If you consistently meets the warning "org.datanucleus.store.appengine.MetaDataValidator warn: Meta-data warning for ****: The datastore does not support joins and therefore cannot honor requests to place related objects in the default fetch group. The field will be fetched lazily on first access. You can modify this warning by setting the datanucleus.appengine.ignorableMetaDataBehavior property in your config. A value of NONE will silence the warning. A value of ERROR will turn the warning into an exception." like this, please add the following line into your jdoconfig.xml:

<property name="datanucleus.appengine.ignorableMetaDataBehavior" value="NONE" />

Although it is quite obvious, but it's the problem where you put it might confuse many people.

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