Difference between Database and Data Source ?

A data source is simply something your program relies on to get data. A database is a kind of data source that persists data to some digitized form. Other data sources include files, services, etc — these all provide data to your programs.

which is better to Packaging EJB in JavaEE 6 WAR vs EAR ?

An important motivation for having EJB beans in a separate JAR is for the age old separation of business logic and view logic. Since EJBs are supposed to concentrate solely on business logic, it makes sense to put them into a separate module. This is exactly what the

What is the difference between EJB2 and EJB3?

EJB2 vs EJB3

EJB (Enterprise JavaBeans) is a Java API (Application Programming Interface) found within Java EE (Java Platform, Enterprise Edition) specification. EJB describes an architectural model for the development of enterprise applications. This is a managed server-side model that is able to capture the business logic of the enterprise application. IBM is EJB’s original creator who developed it in 1997. Sun Microsystems adopted it in 1999.

Before the introduction of EJB, it was found that solutions to problems found in back-end business code were frequently re-implemented by the programmers. As a result, EJB was introduced to address these common problems such as persistence, transactional integrity and security. EJB provides standard ways to handle these back end problems, by specifying how the application server should process transactions, integrate with JPA (Java Persistence API) services, handle concurrency control, handle JMS (Java Message Service) Events, resolve naming issues with JNDI (Java Naming and Directory Interface), develop secure programs with JCE (Java Cryptography Extension) and JAAS (Java Authentication and Authorization Service), deploy components, communicate remotely with RMI-IIOP (Java Remote Method Invocation interface over the Internet Inter-Orb Protocol), develop web services, invoke asynchronous methods and use the Timer service.