Interoperability Features

Interoperability is important in many large enterprise installations of J2EE servers. Specifically, interoperability refers to the ability of software components between dissimilar software or hardware systems to talk with one another.

Difference between J2EE EIS Tier and Interoperability

This is quite different from the features on the EIS tier. While the EIS tier enables the Geronimo-hosted software components to access external systems (which are typically monolithic systems that are not component-based), interoperability features enable two-way communications between Geronimo software components and the external software components. In other words, interoperability implies a more fine-grained and tightly coupled interaction than the EIS-level access. EIS tier refers to access to systems such as relational databases and message queues, while interoperability refers to component-to-component interactions.

CORBA Interoperability

When a client application talks to an EJB in Geronimo, the default protocol used is a proprietary one. This protocol is used by OpenEJB to efficiently access the EJB container. When using this protocol, however, you are restricted to access only via Geronimo J2EE clients.

Through interoperability support, Geronimo extends the accessibility of EJBs for non-J2EE clients and Common Object Request Broker Architecture (CORBA) clients.

CORBA is an interoperability standard based on a specification from the Object Management Group (OMG). The OMG is a group made up of hundreds of global companies, institutions, and individuals who are actively deploying OMG technologies - primarily CORBA. The mission of CORBA is to enable systems with dissimilar hardware, operating systems, and programming languages to work together. The CORBA specification itself is very mature, and working implementations of CORBA exist for many mainframe, industrial control, scientific, and defense applications. You can find more information on CORBA at:

http://www.omg.org/gettingstarted/history_of_corba.htm

The interoperability support in Geronimo 1.1 is performed mainly through RMI-IIOP in JDK 2. RMI-IIOP allows Remote Message Invocation (RMI) based software components to communicate with CORBA clients or servers.

With Geronimo CORBA interoperation, CORBA client applications may access Geronimo-hosted EJBs, and Geronimo-hosted EJBs may access external CORBA-based services.

In addition to communication between CORBA and J2EE components, Geronimo’s implementation also includes a security implementation. The security implementation is the Common Security Interoperation Version 2 (CSIv2) that is specified for CORBA 2.3 and later systems. CSIv2 provides secure, authenticated communications between CORBA- and Geronimo-hosted J2EE components.

Figure 4-7 shows the CORBA interoperability afforded by Geronimo.

Figure 4-7: Geronimo’s CORBA interoperation support

As an administrator, you can configure EJB for CORBA client access; you can also assist in configuration of external access to CORBA components. Chapter 14 shows how to configure Geronimo CORBA inter-operations.