Java EE (JEE or J2EE) tutorials.
See the figure below to see J2EE application server sample class loader hierarchy. As it has been shown in the diagram, “system class path” class loaders are parents of specific class loaders. If parent class loaders are present above “system class path” in hierarchy it means child class loaders have visibility to those classes that have been loaded by parents. However, when a parent class loader is present below “system-Class path” child class loaders will have visibility only into those classes
Updated 01-15-2012 at 08:33 AM by J2EE
A deployment descriptor consists of a XML based text file along with “.xml” extension which describes deployment settings of a component. J2EE application along with modules consists of their deployment descriptor. Attention shall be paid to those elements that have been marked as bold in deployment descriptor files samples, given below. Application.xml: is considered as a standard deployment descriptor of J2EE, which has structural information as following: WEB war modules, EJB jar
Updated 01-14-2012 at 06:41 PM by J2EE
ear, jar and war are standard application deployment archive files. As they are considered standard therefore any kind of application server is well aware that how to deploy or unpack them.
An EAR file (standard JAR file) has an “.ear” extension, which is also known as Enterprise Archive file. J2EE application along with its modules is delivered into EAR file. Other JAR files couldn’t be present in JAR files. However, WAR and EAR files possess JAR files. An EAR file has all WARs and
Updated 01-15-2012 at 08:32 AM by J2EE
MVC or Model View Controller architecture divides display functionality and maintains data to reduce the degree of coupling between components. J2EE MVC
A model presents the state and core business logic. Data present in database is mapped by the model and holds the core business logic.
A View renders model’s contents. Data is accessed by a view from the model and display logic is added for presentation of the
Updated 01-15-2012 at 08:30 AM by J2EE
Multi-tier or 3-tier architectures compel separation between business logic, presentation logic and database logic. Few important benefits are detailed over here:
• Manageability: Every tier can be upgraded, monitored or tuned independently & different duties could be assigned to different tiers.
• Scalability: More hardware could get added up and also permits the clustering that is horizontal scaling.
• Maintainability: Up gradation or other changes are performed
Client tier presents Java, Web browser, or other applications like WAP phone, Applet etc. A request is sent to the Web server by the Client tier. Request is then forwarded to JSP or Servlet, or returns static content in case it is in Web server. Presentation tier summarizes the presentation logic that is required for server clients. A JSP or Servlet present in presentation tier intercepts requests of clients, manages logons, or sessions. Business services are being accessed and finally
Updated 01-15-2012 at 08:29 AM by J2EE
The J2EE platform is basically a multi-tiered system. Functionally, a tier is system’s partitioning. In 3-tier system, every tier has its own unique responsibility. Every tier is loosely coupled and logically separated from each other. J2EE Architecture
Updated 01-15-2012 at 08:28 AM by J2EE
J2EE clients are considered to be those components, services, applications and systems that have access to the J2EE environment so that to access a service or to fulfill a request. Being dependent upon an enterprise J2EE environment’s horizon and scope, there may be simple HTTP requests or complex interactions among different J2EE servers present over the network. J2EE Client Access has following types: Accessing business logic services in EJB: For example, Funds transfer
The J2EE platform comprises of J2EE services, protocols, components and (API) Application Programming Interfaces. Functionality is being provided by J2EE to develop distributed and multi-tiered Web based applications. A J2EE component is considered to be a functional and self contained software unit which has been assembled to J2EE application, along with related files and classes, to do communication with other components. Following components are present in J2EE.