Chapter 20. Distribution and EJB Interoperability

Interoperability Overview

One of the aspects that makes EJB so attractive as a component architecture is that the components can be hosted in containers from different vendors on various platforms and can communicate with one another. For example, you can deploy a JSP page in a Web container from one vendor and invoke operations on a session bean that is deployed in an EJB container provided by a different vendor. One of the containers can be hosted on a Windows platform, and the other might be on a Unix workstation. As an application developer using EJB, you don't have to worry about the location or which platform the server component is hosted on.

You are not required to choose the same vendor for your Web tier container as you have chosen for the EJB container. You are allowed to mix and match so that you get the best performing containers, while at the same time not worrying too much about whether your current enterprise components will run in the container.

This is not to say that there are no issues with mixing vendors; there's always some cost. Container vendors are not perfect, and neither are the specifications that the vendors use to build their containers. However, the interoperability requirements in the J2EE 1.3 and EJB 2.0 Specifications are much clearer than the previous versions about how to accomplish interoperability throughout the enterprise.

The EJB 2.0 Specification includes requirements on EJB container providers that help ensure interoperability for invocations on enterprise beans from various types of clients , including the case where enterprise beans themselves are the clients.