Implementing the Backend Components

WebLogic permits three choices for a backend component: a simple Java class, a stateless session EJB, or a JMS destination. Remember, a web service is composed of a number of operations, and you can implement each operation using any one of these backend component types. Quite often, the operations of a web service are implemented using the remote methods of a stateless session EJB. In a sense, the web service simply wraps the corresponding EJB interface. Stateless session EJBs allow you to encapsulate well-defined business processes, and web services built around a stateless session EJB can provide SOAP clients with an elegant conduit to this business functionality.

Thus, stateless session EJBs are a good choice for implementing the operations of a web service, especially if it is process-oriented and needs to benefit from other J2EE services such as the support for distributed transactions, persistence, security, and concurrency. A Java class is a suitable backend for a process-oriented web service. Creating a Java class requires less effort than building a stateless session EJB. In general, you should consider using standard Java classes for implementing the operations of a web service if you don’t need the support for additional EJB features such as persistence, security, transactions, and concurrency. However, Java classes used as backends for web service operations have certain limitations, which we examine in the next section.

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