---------------------------------------------------------------
- Preferences design considerations.
---------------------------------------------------------------

java.util.prefs.Preferences implementation.

The preferences implementation has been designed to be able to persist the
following preferences structure:

<preferences EXTERNAL_XML_VERSION="1.0">
<root type="user">
<map />
	<node name="user">
	<map />
		<node name="principal1">
		<map />
			<node name="propertyset1">
			<map>
				<entry key="set1prop1" value="256" />
				<entry key="set1prop2" value="314" />
				<entry key="set1prop3" value="540" />
				<entry key="set1prop4" value="63" />
			</map>
			</node>
			<node name="propertyset2">
			<map>
				<entry key="set2prop1" value="256" />
				<entry key="set2prop2" value="314" />
				<entry key="set2prop3" value="540" />
				<entry key="set2prop4" value="63" />
			</map>
			</node>
		</node>
		<node name="principal2">
		<map />
			<node name="propertyset1">
			<map>
				<entry key="set1prop1" value="256" />
				<entry key="set1prop2" value="314" />
				<entry key="set1prop3" value="540" />
				<entry key="set1prop4" value="63" />
			</map>
			</node>
			<node name="propertyset2">
			<map>
				<entry key="set2prop1" value="256" />
				<entry key="set2prop2" value="314" />
				<entry key="set2prop3" value="540" />
				<entry key="set2prop4" value="63" />
			</map>
			</node>
		</node>
		-----
		etc.
		-----
	</node>
	
	<node name="group">
	<map />
		<node name="groupid1">
		<map />
			<node name="propertyset1">
			<map>
				<entry key="set1prop1" value="256" />
				<entry key="set1prop2" value="314" />
				<entry key="set1prop3" value="540" />
				<entry key="set1prop4" value="63" />
			</map>
			</node>
			<node name="propertyset2">
			<map>
				<entry key="set2prop1" value="256" />
				<entry key="set2prop2" value="314" />
				<entry key="set2prop3" value="540" />
				<entry key="set2prop4" value="63" />
			</map>
			</node>
		</node>
		<node name="groupid1">
		<map />
			<node name="propertyset1">
			<map>
				<entry key="set1prop1" value="256" />
				<entry key="set1prop2" value="314" />
				<entry key="set1prop3" value="540" />
				<entry key="set1prop4" value="63" />
			</map>
			</node>
			<node name="propertyset2">
			<map>
				<entry key="set2prop1" value="256" />
				<entry key="set2prop2" value="314" />
				<entry key="set2prop3" value="540" />
				<entry key="set2prop4" value="63" />
			</map>
			</node>
		</node>
		-----
		etc.
		-----
	</node>

</node>
</root>
</preferences>

The idea is to be able to persist group or user principals properties
where properties are logically grouped into property sets.

Therefore, we could have preferences nodes of type user such as:
1. /user/userprincipal1/propertyset1 where propertyset1 contains properties
according to a property set definition.
2. /group/groupprincipal1/propertyset2 where propertyset1 contains properties
according to a property set definition.

Good preferences article: http://www.onjava.com/pub/a/onjava/synd/2001/10/17/j2se.html

---------------------------------------------------------------
- Implementation notes.
---------------------------------------------------------------

- Added the following method to the OJB persistence plugin:

In org.apache.jetspeed.services.perisistence
LookUpCriteria: add(String, java.util.Collection)
PersistencePlugin: deleteByQuery(java.lang.Object)

In org.apache.jetspeed.services.perisistence.impl
OjbLookUpCriteria: add(String, java.util.Collection)
AbstractOJBPersistencePlugin: deleteByQuery(java.lang.Object)

The test were modified to test deleteByQuery.

- Documentation and javadoc can be found under design-docs and docs.

- Implemented java.util.prefs.Preferences spi.

- Updated to checkstyle 3.0.