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A concept called aggregation is commonly used to plug multiple objects together to form one single object at runtime. The main interface in this context is com.sun.star.uno.XAggregation. After plugging the objects together, the reference count and the queryInterface() method is delegated from multiple slave objects to one master object.

It is a precondition that at the moment of aggregation, the slave object has a reference count of exactly one, which is the reference count of the master. Additionally, it does not work on proxy objects, because in Java, multiple proxy objects of the same interface of the same slave object might exist.

While aggregation allows more code reuse than implementation inheritance, the facts mentioned above, coupled with the implementation of independent objects makes programming prone to errors. Therefore the use of this concept is discourage and not explained here. For further information visit http://udk.openoffice.org/common/man/concept/unointro.html#aggregation.

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