1.4 J2EE Platform

1.4 J2EE Platform

-          The J2EE platform uses a distributed multitiered application model for enterprise applications.

-          Application logic is divided into components according to function.

-          the various application components that make up a J2EE application are installed on different machines.

-          depending on the tier in the multitiered J2EE environment.

-          Essentially, J2EE is a collection of APIs that can be used to build such systems.

-          Although this is only half of the picture.

-          J2EE is also a standard for building and deploying enterprise applications.

-          Held together by the specifications of the APIs.

-          That it defines and the services (that J2EE provides).

-          In other words, this means that the "write once, run anywhere" (WORA).

-          J2EE or Java 2 Platform, Enterprise Edition is one of the most powerful ways of developing Multitier web applications.

-          Using the Java 2 Platform, Standard Edition (J2SE) as a basis, Java 2 Platform, Enterprise Edition (J2EE) builds on top of this.

-          To provide the types of services.

-          Sun Microsystems introduce the J2EE application server & Enterprise JavaBeans (EJB) specification as a venture into the multitier component architecture.

-          J2EE function as a middle tier server in three tier architecture.

-          It provides certain specifications that can be used to implement enterprise solution for all types of business requirements.

-          J2EE is also offers cost effective solutions for business requirements.

-          That are necessary to build :

1)      Large scale,

2)      Distributed,

3)      Component based,

4)      Multi-tier applications.

5)       

-          Here are some of the highlights:

• The J2EE security model lets we configure a Web component or enterprise bean so that system resources are accessed only by authorized users.
• The J2EE transaction model lets we specify relationships among methods that make up a single transaction so that all methods in one transaction are treated as a single unit.
• JNDI lookup services provide a unified interface to multiple naming and directory services in the enterprise so that application components can access naming and directory services.
• The J2EE remote connectivity model manages low-level communications between clients and enterprise beans. After an enterprise bean is created, a client invokes methods on it as if it were in the same virtual machine.

The J2EE platform offers the following benefits to the enterprise and to product vendors:

1)      Establishes standards for :

o   Database connectivity

o   Web components

o   Business logic components

o   Message-oriented middleware (MOM)

o   Communication protocols

o   Interoperability

2)      Provides a standard for :

o   Avoiding vendor lock-in

o   Building portable applications

o   Components that are :

                                                              i.      flexible,

                                                            ii.      expandable, and

                                                          iii.       reliable

3)      Also helps in developing secure, scalable, and transactional applications.

4)      Decreases time-to-market.

5)      Because much of the infrastructure and common services are provided by vendors’ products. (That are implemented according to the standard J2EE specification.)

6)      IT organizations can get out of the middleware business and concentrate on building applications for their business.

7)      Increases developer productivity.

8)      Because Java programmers can relatively easily learn J2EE technologies based on the Java language.

9)      All enterprise software development can be accomplished under the J2EE platform, using Java as the programming language.

10)  Promotes interoperability within existing heterogeneous systems, such as :

o   CORBA – ( Common Object Request Broker Architecture)

o   J2EE

11)  Enables developers to focus on supporting business process requirements rather than building the in-house application infrastructure.

12)  The application server handles :

o   Complex tasks of multithreading

o   Synchronization

o   Transactions

o   Resource allocation

o   Life cycle management.

13)  In general, the J2EE platform helps the enterprise to overcome certain issues such as :

o   Programming productivity

o   Application reliability

o   Availability

o   Security

o   Scalability

o   Integration with existing systems.

-  The component-based and platform:

-          Independent J2EE architecture makes J2EE applications easy to write.

-          Because business logic is organized into reusable components.

-          In addition, the J2EE server provides underlying services in the form of a container for every component type.

-          Because we do not have to develop these services werself.

-          We are free to concentrate on solving the business problem at hand.

-          So the container is doing the controlling part of the web components in the web development.

-          Container is the interface.

-          Between a component & its functional behavior.

-          So in order to execute an application the container should be loaded beforehand.