(EnterpriseJavaBeans)
A software component in Sun's J2EE platform, which provides a pure Java
environment for developing and running distributed applications. It is a pure Java
environment for developing and running distributed application.
EJB is a component that is created, controlled and
destroyed by the j2EE container. Each container maintains a pool of EJB instances that are to be assigned to
a client. When the clients no longer needs an Ejb it will return to the pool
and all its resources will be released. The primary purpose of it is to control
and provide services for EJB’s it
contains.
Usage of Ejb provides everything to the developer
that is required for enterprise applications including container managed
persistence, declarative transactions, caching, instance pooling, remote access
etc. It
is server software for modular construction of enterprise software that is to
satisfy the needs of an organisation like schools, business etc. It is an
integral part of information system i.e. it is used in the network of hardware
and software that people use to collect, filter, process and collect data. An EJB web container provides a run time
environment for website related software components including computer
security, Java servlet lifecycle
management, transaction processing, and other web services. Each Bean contains a lifecycle and a set of rules and
provides a boundary between application code and system code. Ejb contains various versions they are: EJB
1.0, EJB 1.1, EJB 2.0, EJB 2.1, EJB 3.0. The current version is EJB 3.1. EJB is of 3 types they are:
1. Session EJB: for mapping
business process flow.
2. Entity EJB: maps a combination
of data and associated functionality.
3. Message driven EJB: activates
only when an asynchronous messages arrive.
With the growth of
the Web and the Internet, more and more enterprise applications are now Web
based, including both intranet and extranet applications. Ejb are most valuable for servicing large no of users over or corporate
networks. Learning Ejb is easy and simple to learn.
An EJB
container is a run-time container for beans that are deployed to an application
server. The container is automatically created when the application server
starts up, and serves as an interface between a bean and run-time services such
as: “Life-cycle
management, Code generation, Persistence management Security, Transaction
management, Locking and concurrency control”.
EJB provides an
architecture to develop and deploy component based enterprise applications
considering robustness, high scalability and high performance. An EJB application can be deployed on any of
the application server compliant with J2EE 1.3 standard specification.
