Enterprise JavaBeans (EJBs) are generally considered a required component of a robust Java 2 Enterprise Edition (J2EE) architecture. Indeed, it does not make sense to invest in J2EE application servers such as WebLogic if one does not plan to manage EJBs. Without EJBs, most of the advanced features in these products – such as clustering, pooling, caching, load balancing and failover – are irrelevant.
The major benefit of EJBs is they force the separation of presentation and business logic in applications. This radically improves application scalability and flexibility, because business logic is centrally located on the server and accessible to any number of user interfaces. And, changes made to the business logic do not impact the client interface, and vice versa.
EJBs are ideally suited to the SOA because they make it relatively easy to expose specific application functionality as business services, via Web Services. Some J2EE applications do not have this EJB tier and instead rely on JavaBeans as their component architecture. In these cases, there is an intermingling of business logic and presentation, which impairs the application’s ability to participate in an SOA. According to Gartner, "To establish services, the business logic must be dissected, then ‘isolated’ from the user interface/forms."1
Mobile applications may be the best illustration of the benefits of EJB. Because EJBs encapsulate business logic and create the necessary isolation from the presentation layer, mobile applications can be deployed on virtually any mobile platform, and changes to the business logic do not impact the mobile clients, and vice versa. With JavaBeans, business logic resides on the client and the server, which means mobile applications, it must be purpose-built for a specific platform, and any change to the business logic requires changes to both the client and server.
As Sun Microsystems explains in its publication, "Java Server Programming – J2EE Edition," "The JavaBeans architecture is meant to provide a format for general-purpose components, whereas the Enterprise JavaBeans architecture provides a format for highly specialized business logic components." Since the SOA requires encapsulating and exposing business logic for consumption by other applications, an EJB layer is a requirement for SOA-ready applications.
HxGN EAM boasts a true J2EE architecture with an EJB layer, enabling customers to gain all the scalability and flexibility benefits that come with EJBs. EJBs also serve as a "future proof," negating the need for HxGN EAM to change business requirements. For example, EJBs can work with any number of clients – including Java Server pages (JSP), Java clients, CORBA, and XML – which protects customers from being locked in to "HTML-only" client architectures. This also means that EJBs can be accessed from virtually any interface, even those of other applications.
Perhaps most important of all, though, is that EJB enables HxGN EAM to interoperate with components that are not part of the J2EE stack, including .Net components. This is a critical capability since, according to Forrester Research, nearly one-third of enterprise applications are written in .Net programming languages.2 This means that J2EE products lacking an EJB layer are simply not practical in the era of the SOA, where it is critical for application components to interoperate.
The Bottom Line:
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EJB is a critical layer for applications participating in SOAs because it encapsulates business logic for use by any number of clients.
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Many J2EE applications lack an EJB layer and use simple JavaBeans as their component architecture. This intermingling of business logic and presentation makes it difficult to extend applications to multiple clients.
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EJB also enables J2EE applications to interoperate with other component architectures, like .Net.
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HxGN EAM is a J2EE application complete with an EJB layer.
1 Gartner, "SOA Will Demand Re-Engineering of Business Applications," Y. Genovese, S. Hayward, J. Comport, Oct. 8, 2004.
2 Forrester, "Of Strategic Languages, Java’s Adoption is Highest," July 12, 2005