J2EE Design Patterns

Name

Transactional Context Pattern

Goal

Allow multiple objects to participate in a single transaction without imposing a large amount of overhead on the programmer (Figure B-20).

Figure B-20. Business delegate and DAOs using the Transactional Context pattern

Participants

Business delegates

Provide access to business logic.

Data access objects

Provide access to persistence resources, such as a database.

Transactional context object

Coordinates activities between business delegates, data access objects, and the underlying database.

Transaction-aware database

Provides system level transaction support.

Interactions

When an application needs to begin a transaction, it obtains a transactional context object from the system and initiates a transaction with the context. All classes with access to the context use it to access transaction-sensitive resources, such as database connections, allowing multiple objects to share a single database transaction.

Notes

This pattern is particularly useful when building servlet-based applications with business delegate and DAO objects. You can associate a transactional context with each request, allowing business delegates to easily manage a transaction involving multiple DAOs and even multiple business delegates. See Chapter 10 for extensive examples.