Three-Level J2EE Architecture
Presentation Level
Application Level (J2EE Platform)
Data Level
PRESENTATION LEVEL
• Contains the graphical user interphase.
• Little to no application logic.
• Is realized using a web browser in many cases.
APPLICATION LEVEL (J2EE Platform)
• Web Server
• Executes application logic.
DATA LEVEL
• ERP Systems
• Databases
The J2EE application server processes clients requests, executes the application logic, and returns the results to the clients. The application data is accessed using the database level.
The application logic is implemented in the form of Enterprise Java Beans. These are executed in an EJB Container, which is part of the J2EE Application Server.
The communication between the client and the J2EE is based on Web standards such as HTTP, HTML, and XML. The J2EE server uses Java Server Pages (JSP) and Java Servlets to generate HTML pages or XML data. Java Server Pages and Java servlets are executed in a Web Container, which is, in turn, part of the J2EE Application Server. Java applets can be included in the HTML pages that are sent to the Web browser. These applets are executed in the browser.
Java Server Pages (JSP) are a technology developed by Sun, which essentially allow the simple dynamic generation of HTML and XML output for a Web server.
This technology allows the embedding of Java code and special JSP actions in static content. This has the advantage that the logic can be implemented independently of the design with this technology. Java Server Pages are converted to Java source code using a special JSP compiler. This source code, which corresponds to a Java servlet, is then converted to bytecode by the Java compiler.
Each application component is executed in a container.
These containers provide the application components with services in accordance with the J2EE specification. Examples of these services are transaction management, availability, security, scalability, client connection, and database access. This means that the developer can concentrate purely on the application logic and does not need to deal with these system functions.
Best regards
Rajnikanth