Composite entity is a Java EE Software design pattern and it is used to model, represent, and manage a set of interrelated persistent objects rather that representing them as individual fine-grained entity beans, and also a composite entity bean represents a graph of objects.
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Structure
there are a number of strategies to implement composite entity pattern. This pattern mainly composites of compsite entity, coarse-grained object,dependent objects.
Composite entity component
Composite entity is the coarse-grained entity bean which may be the coarse-grained object, or may contain a reference to the coarse-grained object.
Coarse-grained object
A coarse-grained object is an object with its own life cycle manages its own relationships to other objects. It can be an object contained in the composite entity, or, composite entity itself can be the coarse-grained object which holds dependent objects.
Dependent objects
It is an object, which can contain other dependent objects (there may be a tree of objects within the composite entity), that depends on the coarse-grained object and has its life cycle managed by the coarse-grained object.
Consequences
According to Oracle description of the pattern, consequences include eliminating inter-entity relationships, improving manageability by reducing entity beans, improving network performance, reducing database schema dependency, increasing object granularity, facilitating composite transfer object creation and overhead of multi-level dependent object graphs.
Drawbacks
The fatal drawback is the requirement of bean-managed persistent (BMP) bean. This involves more work for developers, and create some problems as follows:
Composite entity pattern can only be implemented using BMP or by adding more hand-coded persistence logic to container managed persistence (CMP) beans. These both approaches reduce the maintainability.
Sample code
Sample code for a Professional Service Automation application (PSA) in which the resource object is implemented via composite entity pattern, may look like as follows (entity implements coarse-grained object):