How To Get Free Aim On A Sidekick

EJB3 ( JBoss)

is a JBoss Application Server J2EE of open source implemented in pure Java . Being based on Java, JBoss can be used on any operating system that supports it. Leading developers working for a services company, JBoss Inc., Red Hat acquired in April 2006, founded by Marc Fleury , the creator of the first version of JBoss. The project is supported by a worldwide network of collaborators. The revenues of the company are based on a services business model. JBoss

package implements all J2EE services.

The Enterprise JavaBeans (also known by its acronym EJB) is one of the API as part of standard business application building J2EE of Sun Microsystems (now JEE 5.0 .) Its specification details how the application servers provide objects from the server side are precisely the EJBs:

• remote communication using CORBA

• transactions concurrency control events using
• JMS (Java messaging service) services
• directory names and security
• location of components in an application server.

The Enterprise Java Bean specification defines the roles played by the EJB container and EJBs, as well as having the EJBs in a container.

There are three types of EJBs:

• Entity EJBs ( Entity EJBs): its aim is to encapsulate the server-side objects that stores the data. Entity EJBs have the fundamental characteristic of persistence :
  • container-managed persistence (CMP) the container is responsible for storing and retrieving object data structure through a mapping table database.
  • bean-managed persistence (BMP) entity object itself is responsible, through a database or other mechanism to store and retrieve data referred, therefore, the responsibility implement the persistence mechanisms is the programmer.
• Session EJBs (Session EJBs ): manage the flow of information on the server. Customers generally serve as a front for the services provided by other components available on the server. There may be two types: stateful
  • (stateful ). The stateful session beans are distributed objects that have a state. The state is not persistent, but access to the bean is limited to a single customer.
  • stateless (stateless ). The stateless session beans are distributed objects that have no associated state thereby allowing it the access concurrently. There is no guarantee that the contents of the instance variables are retained between method calls.
• message-driven EJBs ( Message-driven EJBs) are the only beans with asynchronous operation. Using the Java Messaging System ( JMS), subscribe to a topic (topic ) or a queue (queue ) and are activated upon receiving a message addressed to the topic or queue. Instantiation does not require client-side.

The EJB specification has evolved at the same time did the J2EE specification itself. Different versions that have existed to date are:

• EJB 1.0: the original specification
• EJB 1.1: the first included within
• J2EE EJB 2.0, including J2EE 1.3, added the local interfaces and Message-Driven Beans.
• EJB 2.1, including the latest revision of J2EE 1.4.
• EJB 3.0: Now with Cluster and is included in JEE 5.0

There is a proposal for a review of the Enterprise JavaBeans specification, the EJB 3.0, which aims to simplify the deployment of beans without sacrificing power and flexibility.

The new EJB 3.0 specification simplifies the process of EJB creation and facilitates the implementation of persistence.

This specification will be available in the new version of J2EE JEE named 5.0.