What are the uses of "Enterprise JavaBeans"?

Replies

• 

  ramzraja

  Some time back, I read an article by Ed Roman on the same subject. I think it is available in the archives of theserverside.com. The key points from that article and some other places are given below:
  
  The definition of EJB states that it is a distributed, transactional, persistent software component written in Java Programming Language. From this definition, it can be derived that EJBs are required in the following scenarios.
  
  i. When the application is distributed: When the resources and data are distributed across multiple sites, then it is ideal to go for an application that is based on EJBs. Choose EJB when you know your application will need to scale beyond initial low usage levels and support multiple, concurrent users.
  
  ii. When the application is performance-centric, use of EJBs and the application server provide high performance and very good scalability.
  
  iii. Declaratively manage transactions. When transaction management is required to ensure data integrity, EJBs may be used. In EJB, you merely specify whether a bean's methods require, disallow, or can be used in the context of a transaction. The EJB container will manage your transaction boundaries appropriately. In a purely servlet architecture, you'll have to write code to manage the transaction, which is difficult if a logical transaction must access multiple DataSources.
  
  iv. Declaratively manage security. The EJB model allows you to indicate a security role that the user must be assigned to in order to invoke a method on a bean.
  
  v. Separation of Business Logic. The most significant difference between a web application using only servlets and one using servlets with EJBs is that the EJB model mandates a separation between display and business logic. This can be achieved using Servlets and DAO also
  
  Hope it helps.
• 

  PraveenKumar Purushothaman

  EJBs are used in the following scenarios:
  
  In a Web-centric application, the EJBs will provide the business logic that sits behind the Web-oriented components, such as servlets and JSPs. If a Web-oriented application requires a high level of scalability or maintainability, use of EJBs can help to deliver this.
  
  Thick client applications, such as Swing applications, will use EJBs in a similar way to Web-centric applications. To share business logic in a natural way between different types of client applications, EJBs can be used to house that business logic.
  
  Business-to-business (B2B) e-commerce applications can also take advantage of EJBs. Because B2B e-commerce frequently revolves around the integration of business processes, EJBs provide an ideal place to house the business process logic. They can also provide a link between the Web technologies often used to deliver B2B and the business systems behind.
  
  Enterprise Application Integration (EAI) applications can incorporate EJBs to house processing and mapping between different applications. Again, this is an encapsulation of the business logic that is needed when transferring data between applications (in this case, in-house applications).
  
  These are all high-level views on how EJBs are applied. There are various other EJB-specific patterns and idioms that can be applied when implementing EJB-based solutions.
• 

  synergynext

  good stuff Praveen and ramzraja
  to answer other 2 questions,
  server installation - Install an Enterprise JavaBeans Server
  which database - oracle is widely used
• 

  PraveenKumar Purushothaman

  Oracle with EJB is the best pair... 😀