Core J2EE Pattern Catalog

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Last Updated:
January 29, 2006 8:54 PM


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Term Description
BMP Bean Managed Persistence
CMP Container Managed Persistence
Composite A complex object that holds other objects. Also related to the Composite pattern described in the GoF book.

Controller Interacts with a client, controlling and managing the handling of each request.

Data Access Object An object that encapsulates and abstracts access to data from a persistent store or an external system.
Delegate A stand-in, or surrogate, object for another component; an intermediate layer. A Delegate has qualities of a proxy and façade.
Dependent Object An object that does not exist by itself and whose lifecycle is managed by another object.
Dispatcher Some of the responsibilities of a Controller include managing the choice of and dispatching to an appropriate View. This behavior may be partitioned into a separate component, referred to as a Dispatcher.
Enterprise Bean Refers to an Enterprise JavaBean component; can be a session or entity bean instance. When this term is used, it means that the bean instance can be either an entity or a session bean.
Façade A pattern for hiding underlying complexities; described in the GoF book.
Factory (Abstract Factory or Factory Method) Patterns described in the GoF book for creating objects or families of objects.
Iterator A pattern to provide accessors to underlying collection facilities; described in the GoF book.
GoF Gang of Four—refers to the authors of the popular design patterns book, Design Patterns: Elements of Reusable Object-Oriented Software, by Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides. [GoF]
Helper Responsible for helping the Controller and/or View. For example, the Controller and View may delegate the following to a Helper: content retrieval, validation, storing the model or adapting it for use by the display.
Independent Object An object that can exist by itself and may manage the lifecycles of its dependent objects.
JDO Java Data Objects
JMS Java Message Service
MDB Message Driven Bean
Model A physical or logical representation of the system or its subsystem.
Persistent Store Represents persistent storage systems such as RDBMSs, ODBMSs, file systems, and so forth.
POJO Proxy A pattern to provide a placeholder for another object to control access to it; described in the GoF book.
Scriptlet Application logic embedded directly within a JSP.
Session Bean Refers to a stateless or stateful session bean. May also refer collectively to the session bean’s home, remote object, and bean implementation.
Singleton A pattern that provides a single instance of an object, as described in the GoF book.
Template Template text refers to the literal text encapsulated within a JSP View. Additionally, a template may refer to a specific layout of components in a display.
Transfer Object A serializable POJO that is used to carry data from one object/tier to another. It does not contain any business methods.
View The View manages the graphics and text that make up the display. It interacts with Helpers to get data values with which to populate the display. Additionally, it may delegate activities, such as content retrieval, to its Helpers.
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