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J2EE, which stands for Java 2 Platform, Enterprise Edition, was a platform and set of specifications for developing large-scale, distributed, and multi-tiered enterprise applications using the Java programming language. Originally developed by Sun Microsystems, it was later rebranded as Java EE and is now known as Jakarta EE, managed by the Eclipse Foundation. The platform was created to simplify the development of complex business applications by providing a standardized, modular, and component-based approach.
The J2EE architecture is typically organized into a multi-tiered model, which separates an application into logical layers to improve scalability, reliability, and security:
- Client Tier: This is the user-facing part of the application, which could be a web browser using HTML, a Java applet, or a standalone application client.
- Web Tier: This layer handles the user requests and responses. Key technologies here include Java Servlets for generating dynamic content and JavaServer Pages (JSP) for creating web pages with embedded Java code.
- Business Tier: This is the core of the application where the business logic resides. It is composed of Enterprise JavaBeans (EJBs), which are server-side components that handle complex tasks like transaction management, security, and data persistence.
- Enterprise Information System (EIS) Tier: This layer includes the databases and legacy systems that store and manage an organization’s data.
The strength of J2EE lies in its extensive set of APIs and services that handle many of the complexities of enterprise development automatically. This allows developers to focus on the business logic rather than on low-level system details. Some of the key technologies and services within J2EE include:
- Enterprise JavaBeans (EJB): A component model for creating reusable, secure, and transactional business logic.
- JavaServer Pages (JSP) and Servlets: For building dynamic web applications.
- Java Database Connectivity (JDBC): A standard API for connecting to and interacting with databases.
- Java Naming and Directory Interface (JNDI): A service that allows application components to discover and look up other resources and components.
- Java Message Service (JMS): For enabling asynchronous communication between different parts of a distributed application.
By providing a standardized platform, J2EE ensured application portability, meaning an application developed on one J2EE-compliant server could be deployed on another without significant changes. The platform’s robust set of features made it a popular choice for building applications in high-stakes industries like finance, telecommunications, and e-commerce, where scalability and reliability are paramount.
