Query Service (Java Enterprise in a Nutshell)

11.10. Query Service

The Query Service provides a general object query mechanism for distributed objects. With this service, collections of objects can be searched to generate subcollections, or subsets of objects within a collection can be deleted or updated through a query. The facilities defined in the Query Service can be mapped to, but are not limited to, persistent storage facilities, such as relational or object databases.

Collections of objects are represented by Collection objects, which are created using a CollectionFactory. You iterate through a Collection of objects using an Iterator. QueryEvaluator objects issue a Query against a given Collection. The result of evaluating a Query can be of any type, but typically it is a Collection of some kind. A QueryManager is a type of QueryEvaluator that allows you to create queries.