Enterprise Java Beans

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  • Topic: Enterprise JavaBean, Java, Java Platform, Enterprise Edition
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  • Published : April 11, 2011
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Enterprise JavaBeans
A Component Development Model

Dan Ochieng' Odhiambo

Component Based Software Development, SSE 402
Mr. Peter Kimemiah
March 1, 2011

Enterprise JavaBeans:
Enterprise JavaBeans (EJB) is a managed, server-side component architecture for modular construction of enterprise applications. The enterprise application developer may build his/her application as a set of interconnected enterprise beans and deploy such an application in an EJB-compliant application server. The specification also mandates that EJB-compliant application servers provide a set of enterprise services through well-defined Java interfaces. The standard also specifies certain interfaces that all developer-written components should implement in order for them to be deployed in an EJB-compliant application server. In other words, the EJB server promises a set of services and, in return, expects the components (enterprise beans) to implement certain interfaces so the server may manage these components. The EJB standard enables the enterprise developer to focus on the actual business logic of the application, encoded in the beans, and the EJB server is responsible for all the enterprise services such as Concurrency, Persistence, Transaction Management, Security Management, Naming Services, Object Distribution and Resource Management. EJB based applications are secure, robust, scalable, portable and transactional. Benefits of EJB

EJB simplifies the development of small and large enterprise applications. The EJB container provides system-level services to enterprise beans, the bean developer can just concentrate on developing logic to solve business problems. Organization Responsible for maintaining EJB Component model Standards: Sun's Microsystems that was currently bought by Oracle Corporation Terminologies used in describing of EJB

Session Bean
Session is one of the EJBs and it represents a single client inside the Application Server. Stateless session is easy to develop and its efficient. As compared to entity beans session beans require few server resources. A session bean is similar to an interactive session and is not shared; it can have only one client, in the same way that an interactive session can have only one user. A session bean is not persistent and it is destroyed once the session terminates. Session Beans are of two types, Stateful Session Bean and Stateless Session Bean. Stateless Session Bean

A stateless session bean does not maintain a conversational state for the client. When a client invokes the method of a stateless bean, the bean's instance variables may contain a state, but only for the duration of the invocation. Because stateless session beans can support multiple clients, they can offer better scalability for applications that require large numbers of clients. Typically, an application requires fewer stateless session beans than stateful session beans to support the same number of clients. Stateful Session Beans

The state of an object consists of the values of its instance variables. In a stateful session bean, the instance variables represent the state of a unique client-bean session. Because the client interacts ("talks") with its bean, this state is often called the conversational state. Entity Bean

Entity beans are persistence java objects, whose state can be saved into the database and later can it can be restored from Data store. Entity bean represents a row of the database table. Message Driven Bean

Message Driven Bean is an enterprise bean that can be used by JEE applications to process the messages asynchronously. Message Driven Bean acts as message consumer and it receives JMS messages. History of Enterprise JavaBeans

EJB 3.1, final release (2009-12-10)JSR 318. The purpose of the Enterprise JavaBeans 3.1 specification is to further simplify the EJB architecture by reducing its complexity from the developer's point of view, while also adding new functionality in...
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