In this article on Understanding Enterprise Java Beans, I will explain the concept of Enterprise Java Beans and their role in building a Java Enterprise application.
Basically, an Java Enterprise application that makes use of Java EE technology happens to be a multi-tier application. Further, the enterprise-level applications must be scalable and robust. Often these applications consist of several tiers with each tier performing a specific function in the application. Furthermore, we can build the different tiers of an enterprise-level application using software components. EJB (Enterprise Java Beans) technology provides us with a mechanism to develop the application using components.
What are Enterprise Java Beans (EJB)?
In fact, Enterprise Java Beans (EJB) provides us with a development architecture to build the application using reusable software components. As a matter of fact, these components reside on the server and implement business logic. Also, the use of EJB in applications makes the application distributed in nature. Because the EJB components are distributed, they can be accessed by a remote client. Since, EJB components are responsible for implementing business logic rather than client, which can be a JSP or servlet, the client developers can focus on developing the presentation logic. Hence, the use of EJB in an application supports the separation of concerns so that we can develop and maintain each part of the application separately without affecting the whole application.
Another advantage of using EJB is that we can have a thinner client that comprises lesser functionality. Therefore, the client can efficiently run on smaller devices. The following figure demonstrates the EJB architecture. As can be seen, the application client that may be a servlet or another bean communicates with the bean using a remote or home interface. The beans run in EJB container that the application server provides. Basically, the EJB container is a software component that provides various services like transaction management, lifecycle management, and so on.
However, EJB has some drawbacks also. For instance, deploying EJB requires an application server. Hence, it adds cost to application development. Furthermore, it requires a Java client only. For any other client, we need a web service. Also, EJB has complex architecture. Hence, it requires expertise. All these things make the application costlier. It also increases development time.
Besides these drawbacks, EJB is a robust technology. Because it makes the development of large applications easier and simplified.