How Do I Deploy an EJB?

After an EJB is packaged, it can be deployed in an appropriate J2EE server. There is no limit to the number of times an EJB can be deployed as a part of different applications.

Remember that J2EE defines a separate role for the application deployer. It may be that for particular installations, databases, or other resource names need to be changed to match the local environment. When configuring the application, the deployer can alter this EJB or enterprise application metadata.

Plugging into the Container

When an EJB is deployed into a particular EJB container, the EJB must be plugged into that container. To do this, an EJBObject must be generated based on the EJB's remote interface. This EJBObject will be specific to that EJB container and will contain code that allows it to interface with that container to access security and transaction information. The container will examine the metadata supplied with the EJB to determine what type of security and transaction code is required in the EJBObject.

The container will also generate the home interface implementation so that calls to create, find, and destroy EJB instances are delegated to container-defined methods.

The container will examine the EJB and enterprise application metadata and hook up resource references. It will also provide an environment for the application components.

Finally, the container will register the home interface of the EJB with JNDI. This allows other application components to create and find EJBs of this type.

Performing the Deployment

As mentioned previously, when deploying an EJB or enterprise application, the application developer taking on the J2EE role of deployer can choose to alter certain of the metadata relating to the configuration of the application. Although this can be done manually, it is usually done through a GUI tool to make things easier and to keep things consistent.

After the EJB has been deployed, any subsequent changes to its functionality will mean that the EJB must be re-deployed. If the enterprise application or EJB is no longer needed, it should be undeployed from the container.