Extensions : Persistence Properties


DataNucleus is developed as a plugin-driven framework and one of the components that is pluggable is to allow definition of persistence properties. These properties are used by plugins and allow configurability of behaviour. Any plugin can define its own properties.

You can define persistence properties using the plugin extension org.datanucleus.persistence_properties.

Plugin Specification

The only thing required is to register the persistence property with DataNucleus via the plugin.xml. Heres an example

<?xml version="1.0"?>
<plugin id="mydomain" name="DataNucleus plug-ins" provider-name="My Company">
    <extension point="org.datanucleus.persistence_properties
        <persistence-property name="datanucleus.magicBehaviour" value="false" validator="org.datanucleus.properties.BooleanPropertyValidator"/>">

Note that you also require a MANIFEST.MF file as per the Extensions Guide. Note also

  • If you specify the attribute datastore as true in the plugin.xml then your property will be stored with the StoreManager (instead of NucleusContext where it would normally be stored).
  • If you specify the attribute manager-overrideable as true in the plugin.xml then the user can specify this property additionally on the PM/EM (rather than just on the PMF/EMF)
  • The validator attribute is optional but allows you to define a class that validates the values it can be set to.

Plugin Usage

Now you can access this property from within your DataNucleus plugin via

boolean magic = nucleusCtx.getPersistenceConfiguration().getBooleanProperty("datanucleus.magicBehaviour");

// or from the StoreManager
boolean magic = storeMgr.getBooleanProperty("datanucleus.magicBehaviour");