Java Interview Questions

The J2EE technologies can be divided according to use as

The component Technologies.

The Service Technologies.

The communication Technologies.

The component Technologies.

These technologies used to uphold most important part of Application i.e. Business Logic. There are three types of components.

Servlets and JSP and Enterprise JavaBeans .

The Service Technologies

Provide the Application’s components with supported services to function efficiently.

JDBC, JTA and JNDI.

The Communication Technologies

Provides the mechanisms for communicating among different parts of the applications, whether they are local or Remote.

1.Internet Protocols like http,TCP/IP and SSL

2. Remote Object Protocols like RMI and RMI/IIOP, JavaIDL, JMS, JavaMail and XML

Developing J2EE Applications

1. Application component development
2. Composition of Application Components into modules
3. Composition of modules into Applications
4. Application Deployment

Deployment Roles

1. J2EE Product Provider
2. Application Component Provider
3. Application Assembler
4. Deployer
5. System Administrator
6. Tool Provider

The Architecture of a container can be divided into four parts
1. Container contracts
2. Container service APIs
3. Declarative Services
4. Other Container Services

Container contracts

The basic purpose of container in J2EE architecture is to provide runtime environment for application components. The application components are always Remote to client. The container process is the only entry point into the components. Hence it is required to follow the contract specified by the Container.

In J2EE the contract is in the form of interfaces and classes that implements or extends to standard APIs

Container Service APIs

J2EE containers provide a service level abstraction of the APIs so that  we can access the service APIs such as JDBC, JTS, JNDI,JMS etc., within the container as though  the underlying container were implementing them.

Declarative Services

A deployment descriptor defines the contract between the container and component. The purpose of this approach is to minimize the application programming required in order to make use of services provided.

Other Container Services

1. Life Cycle Management  of  Application Components.
2. Resource Pooling.
3. Population of JNDI name space based on deployment names associated with EJB components.
4. Population of JNDI name space with objects necessary for utilizing container service APIs.
5. Clustering

It is an XML file that describes the application components and additional information required by container to manage the application components effectively