J2EE web container

Provide an overview of web container.

- The web container is used to implement the web components functionality.

- The functionality specifies an environment, called as runtime environment which the web components security, deployment, life-cycle management transaction management, request-response services.

- A container manages the servlet / JSP/ EJB functionality.

- J2EE server runs the components and the containers.

- A web container will also manage the database connection pooling, data persistence and access to the J2EE API.

Explain the Java Servlet programming model.

- The servlets are server side components in a web application.

- These components platform independent and on any server as the java technology is platform independence.

- The servlets are dynamically loaded by the JRE of servlets.

- When a request is received from a client, the web container / web server will ignite the servlet. The servlet processes the request and sends the response back to the container / web server which in turn it sends the response back to the client.

Describe in brief about deployment descriptors.

- A deployment descriptor describes the configuration information to deploy a web application.

- For a web application, it directs the deployment tool that is to deploy a module for a specific container such as ejb container / servlet/jsp container.

- For web applications the deployment descriptor is web.xml and must be placed in a WEB-INF directory of a web application root directory.

- For EE deployment descriptor the name should be application.xml and must be placed in a META-INF directory at the top level of the application .ear file.

Explain the J2EE container architecture.

J2EE Container Architecture:

- The J2EE application components needs support at runtime.

- This support is provided by J2EE containers.

- They use protocols, methods of the containers to access other application components.

- The containers of J2EE are:

1. Web Container
2. EJB Container.

1. Web Container:

- It is used to host web applications.
- It provides the run time environment to execute Servlet and JSP component types.

2. EJB Container:

- The business logic is dealt by the server components called EJB components.
- The access to local and remote enterprise beans is provided by the EJB container.
- The operations of the three beans namely Entity Bean, Session Bean and Message-driven bean are handled by the EJB Container.