Добавил:
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз: Предмет: Файл:
Enterprise JavaBeans™ Specification, Version 2.0 - Sun Microsystems.pdf
Скачиваний:
14
Добавлен:
24.05.2014
Размер:
2.71 Mб
Скачать

Sun Microsystems Inc.

Overview

Enterprise JavaBeans 2.0, Public Draft

Standard mapping to CORBA protocols

entity’s state is automatically reset to the state of the last committed transaction. The crash is not fully transparent to the client—the client may receive an exception if it calls an entity in a container that has experienced a crash.

A typical EJB Container and Server provide a scalable runtime environment for a large number of concurrently active entity objects.

4.3.3 Message-driven objects

A typical message-driven object has the following characteristics:

Executes on receipt of a single client message.

Can be transaction-aware.

May update shared data in an underlying database.

Does not represent directly shared data in the database, although it may access and update such data.

Is relatively short-lived.

Is stateless.

Is removed when the EJB Container crashes. The container has to re-establish a new mes- sage-driven object to continue computation.

A typical EJB Container provides a scalable runtime environment to execute a large number of mes- sage-driven objects concurrently.

4.4 Standard mapping to CORBA protocols

To help interoperability for EJB environments that include systems from multiple vendors, the EJB 2.0 specification requires compliant implementations to support the interoperability protocol based on CORBA/IIOP for invocations from J2EE clients on Sessions Beans and Entity Beans through their Home and Remote interfaces. Implementations may support other remote invocation protocols in addition to IIOP.

Chapter 18 summarizes the support for distribution and the interoperability requirements for EJB 2.0.

5/31/00

46