Java/Advanced Java

Full form of EJB is Enterprise JavaBeans. It is a non visual component of a distributed system and provides a specification for creating server-side scalable, transactional enterprise-level applications. It provides a consistent component architecture framework for creating distributed n-tier middleware.

Few advantages of EJB are:

1. It allows the programmers to build distributed applications by combining various components which have been developed by using different tools.

2. It enables the programmers to go away with the low level details of the transactions and thus making it very easy and simple to work with.

3. The components can be developed once in this and can be implemented again and again thus saving lot of time and efforts of the programmers.

An EJB architecture consists of few components which are:

1. EJB server,

2. EJB containers that

3. EJB that run in these containers,

4. EJB clients

There are two types of EJBs. They are as under:

1. Session Beans

2. Entity Beans

Session Beans: Session Bean is usually associated with one EJB Client. Each Bean is created and destroyed by the particular EJB Client that it is associated with. The session bean can have either a state or it can be stateless and they exist only till the system is not closed.

Entity Beans: Unlike the session bean, the entity Beans always have states and they can exist even after the system is closed and shut down. Each Entity Bean can be shared by multiple EJB Clients. Their states can be persisted and stored across multiple invocations.

The Full form of JDO is Java Data Objects. They provide the programmers with an interface based definitions to data stores and transactions. They provide with a way to store the Java objects in the transactional data stores. It works on all the Java Platforms. It gives the flexibility to the programmers to write their own logic and queries. Advantages of implementing JDO:

1. It is very easy to be implemented by the programmers as the programmers don’t have to worry about the storage of the data in the application.

2. The applications which are developed using this are flexible enough that they can be executed on multiple implementations.

3.It provides very high efficiency and performance when implemented in the applications.

4. Database independence: Applications written with the JDO API are independent of the underlying database. JDO implementations support many different kinds of transactional data stores, including relational and object databases, xml, flat files, and others.

5. They can very easily be integrated with the EJB Features too.

Java Message Service (JMS) is also known as message-oriented-middleware . It simplifies application development by providing a very simple interface to create, send, receive and read messages in any distributed Enterprise System. It acts as a standard Java based interface to the message services.

It is classified into various types:

1. Public Subscribe messaging

2. Point-to-point messaging

3. Request Reply Messaging

Java Server Pages (JSP) technology helps the programmers to develop and design the web pages for the various systems. These applications are also platform independent and works on the MVC architecture. It separates the user interface from the content generation through which the programmer has the feasibility to dynamically change the pages without much trouble.

Advantages of JSP:

1. JSP can be very easily learnt and implemented by the programmers.

2. Pages written in JSP can be very dynamically developed and maintained.

3. JSP makes it possible to use various HTML tools such as Macromedia Dreamweaver etc.

4. It is portable to multiple servers and operating systems.

Advantages of servlets are :

1. They provide the programmers with an extensive infrastructure to work on

2. Servlets provide the programmer with the opportunity to perform various things which were not possible with regular CGI.

It is a text-based markup language which has got ample amount of acceptance from the programmers for the data interchange on the web. In HTML, we identify data using tags (identifiers enclosed in angle brackets: <...>). Collectively, the tags are known as markup. But unlike HTML, XML tags identify the data rather than specify how to display it. It puts a label on a piece of data that identifies it (for example, <message>...</message>). There are several basic ways to use XML:

• Traditional data processing, where XML encodes the data for a program to process

• Document-driven programming, where XML documents are containers that build interfaces and applications from existing components

• Archiving--the foundation for document-driven programming--where the customized version of a component is saved (archived) so that it can be used later

• Binding, where the DTD or schema that defines an XML data structure is used to automatically generate a significant portion of the application that will eventually process that data

Advantages of XML:

1. Since it is wriiten in simple plain text it is very feasible for the programmer to edit the files in nay text editor.

2. It can also store large amount of data too along with the text.

3. Stylesheets can also be easily implemented in XML.They can be once designed and then repeatedly implemented again and again with just few modifications.

4. We can implement the links very much similar to the HTML linking.