So far, we've looked at caching objects through WebSphere eXtreme Scale using the ObjectMap API. ObjectMap provides a useful caching API for simple POJOs that do not have relationships between classes. This works well for simple object models, but sometimes we need to work with classes that have relationships between them. WebSphere eXtreme Scale provides the Entity API for the times we need to work with more complex object models. This allows us to group objects together in the grid by using their relationships to group them in a meaningful way. Related objects are stored together in the grid. Though this may not seem important working with a local ObjectGrid instance, it becomes extremely important when we work with distributed ObjectGrids.
The Entity API lets us define relationships between classes so that ObjectGrid can manage those relationships when caching objects. It lets us work with POJOs instead of making us write boilerplate code to manage relationships...