1.1 Introduction to J2EE

1.1 Introduction to J2EE

-          Java is one of the most commonly used and mature programming languages for building enterprise applications.

-          Over the years, Java development has evolved from small applets run on a Web browser to large enterprise distributed applications run on multiple servers.

-          Now, Java has three different platforms, or flavors, and each addresses certain programming requirements:

1)      J2SE :

v  The Java 2 Platform, Standard Edition (J2SE) is the underlying base platform for the J2EE.

v  The J2SE platform consists of the Java 2 Software Development Kit (SDK) and the Java 2 Runtime Environment (JRE).

v  J2SE includes tools and application programming interfaces (APIs) for developing client applications with graphical user interfaces (GUIs), database access, directory access, Common Object Request Broker Architecture (CORBA), fine-grained security, input/output functions, and many other functions.

2)      J2EE :

v  The Java 2 Platform, Enterprise Edition (J2EE) is a platform for building server-side components and applications.

v  It provides the infrastructure needed for these applications through a set of common services.

v  J2EE is a platform and an industry-accepted standard that enables solutions for developing and deploying multitier enterprise applications.

v  It provides a unified platform for building distributed, server-centric systems.

v  J2EE is a set of standard APIs that is offered by a vendor through products and tools to be used by the enterprise.

v  It was developed to meet recent enterprise requirements to the complexity of business processes. such as :Diversity of both

o   applications and

o   Data

3)      J2ME :

v  The Java 2 Platform, Micro Edition (J2ME) helps with building Java applications for micro-devices with limited display and memory requirements.

v  The entire API fits into 1KB, such as :

o   Wireless devices

o   PDAs

o   Network devices

-          Promises of Java apply for enterprise applications too:

·         Enterprise applications can be run on different platforms.

·         Supporting the Java 2 platform.

·         Enterprise applications are portable.

·         Between application servers supporting the J2EE specification.

  What does J2EE comprise (Include/involve)?

-          J2EE is comprised of many APIs used to build enterprise applications.

-          Although the total list of APIs initially seems overwhelming.

-          It is worth bearing in mind that :

1)      Some are primarily used by the J2EE environment. ( in which wer application executes),

2)      While some provide services. (that wer specific application may not require).

-          Therefore, it is worth remembering that we don't have to use all of them.

-          For completeness, however, the full list of technologies that make up J2EE is as follows:

• Java Servlets
• JavaServer Pages (JSP)
• Enterprise JavaBeans (EJB)
• Java Message Service (JMS)
• Java Naming and Directory Interface (JNDI)
• Java Database Connectivity (JDBC)
• JavaMail
• Java Transaction Service (JTS)
• Java Transaction API (JTA)
• J2EE Connector Architecture (J2EE-CA, or JCA)

-          From a developer perspective, the main technologies are :

1)      EJB,

2)      JSP,

3)      Java Servlets,

4)      JDBC and JMS,

5)      Although JNDI is used for locating EJBs and

6)      Other enterprise resources.

-          As this is about web application development, there is always two sides:

1)       as Client &

2)      Server.

-           In the client side the:

1)      java pages,

2)      html pages are running .

-          And  in the server side :

1)      Java Server Pages (JSP) ,

2)       Servlets,

3)      Enterprise Java Beans (EJB) are running.

-           So tiers made them separate from each other

-          And also give a clear way to communicate each other.