The JEE platform provides the environment to develop enterprise applications / services using multitier architecture. The highly intensified technology made the need for scalable, efficient, faster solutions for information management. The JEE technology is rightly apt for meeting these requirements. JEE provides a programming development environment which improves the productivity of development, standards for hosting / deploying enterprise applications.
The following are the tiers in JEE application
Client Tier: The client tier includes the web components such as Servlets, JSP or standalone Java Desktop applications. This tier provides dynamic interfaces to the middle tier.
Middle Tier: This also called as the server tier. In the middle tier enterprise beans and web services encapsulate distributable business logic for the applications which are reusable. The JEE application server contains the server-tier components which provides the platform for these web components for actions to be performed and data to be stored / persisted.
Enterprise data tier: The enterprise level data is stored / persisted preferably or typically in a relational database, in this tier.
The JEE applications comprises of components, containers and services. All the web components (Servlets, JSP) provide dynamic requests and responses from a web page. The EJB components contain the server-side business logic for enterprise applications.
What is J2EE?
J2EE means Java 2 Enterprise Edition. The functionality of J2EE is developing multitier web-based applications .The J2EE platform is consists of a set of services, application programming interfaces (APIs), and protocols.
Tell me more about application clients and applets.
An application client is a first-tier client component with access to certain APIs. An “application client module” contains class files, a deployment descriptor, and it is packaged as a JAR file. An “application client container” is simply a container that supports application client components.
Applets characteristically execute in web browsers with Java Plugins, but they can execute anywhere that supports the applet programming model. As with an application client container, an “applet container” is one that supports applet programming.
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.
The web container is used to host web applications. It provides the run time environment to execute Servlet and JSP component types./li>
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.
What is the MVC on struts.
MVC stands Model-View-Controller.
Model: Model in many applications represent the internal state of the system as a set of one or more JavaBeans.
View: The View is most often constructed using JavaServer Pages (JSP) technology.
Controller: The Controller is focused on receiving requests from the client and producing the next phase of the user interface to an appropriate View component. The primary component of the Controller in the framework is a servlet of class ActionServlet. This servlet is configured by defining a set of ActionMappings.