Working with properties
If the Properties module is configured correctly and the services are wired, the properties of a specific entity can be read and set as follow:
Foo foo = new Foo( "aFoo" );
UserProperties userProperties = userPropertiesService.getProperties( userId );
Set<Foo> foos = userProperties.getValue( "userFoo" );
foos.add( foo );
userPropertiesService.saveProperties( userProperties );
Note that properties should always be saved after updating.