Java 2 Platform, Enterprise Edition (J2EE) Overview

Sun Microsystems set a new standard for client-side computing with the Java 2 Platform, Standard Edition (J2SE). Experience with the J2SE platform, plus input from enterprise software vendors and developers, led to development of the Java 2 Platform, Enterprise Edition (J2EE). The J2EE platform includes four deliverables: the J2EE specification, a J2EE reference implementation, a Compatibility Test Suite, and the Enterprise Java BluePrints.

Subjected to close scrutiny and feedback from a variety of enterprise technology leaders and the industry at large, the J2EE specification defines a consistent yet flexible approach to implementing the platform. The J2EE specification enumerates the APIs to be provided with all J2EE platforms and includes full descriptions of the support levels expected for containers, clients, and components. It defines a flexible standard that can be built on either a single system or deployed across several servers, each providing a specific set of J2EE support services. This means a wide range of existing enterprise systems already in use throughout industry will be able to support the J2EE platform.

Key to validating the Java 2 Platform, Enterprise Edition, the J2EE reference implementation is a complete implementation of the J2EE specification and is used by system vendors to compare with their own implementations.

The J2EE SDK is built on the J2EE reference implementation and provides application developers with a way to familiarize themselves with J2EE technology as they explore full-scale deployment of J2EE applications. The J2EE 1.4 SDK includes the J2EE 1.4 reference implementation, the J2SE SDK, and various tools to help developers prototype J2EE applications and learn about the J2EE platform and technologies.

By providing a means to fully test implementations of the platform standard, the Compatibility Test Suite ensures consistent implementation across various vendor offerings. For application developers, this means full portability for enterprise applications. The suite includes tests for all classes and methods required by the J2EE specification. It also includes end-to-end tests to check that all layers of a J2EE application will interact correctly and consistently. There are over 20,000 tests in the CTS, including tests for WS-I interoperability.

Provided as both documentation and complete examples, the Enterprise Java BluePrints describes and illustrates "best practices" for developing and deploying component-based enterprise applications in the J2EE platform. Topics explored include component design and optimization, Web services, division of development labor, and allocation of technology resources.

In addition to providing support for Enterprise JavaBeans and Java Servlets and JavaServer Pages components and Web services APIs, the J2EE platform specification defines a number of services for use by J2EE components.

Designed to standardize access to a variety of naming and directory services, the Java Naming and Directory Interface (JNDI) API provides a simple mechanism for J2EE components to look up other objects they require.

JDBC API enables applications to manipulate existing data from relational databases and other data repositories. The J2EE platform includes the latest implementation of the JDBC API -- version 3.0. This new technology includes handling of SQL User-Defined Types (UDTs), rowset manipulation, connection pooling, and distributed transactions support.

The J2EE Deployment API defines standard APIs to enable deployment of components and applications based on the J2EE platform, as well as the development of platform-independent deployment tools.

The Java Authorization Contract for Containers (Java ACC) specification defines new java.security.Permission classes to satisfy the J2EE authorization model. The Java ACC specification defines the binding of container access decisions to operations on instances of these permission classes. It defines the semantics of policy providers that employ the new permission classes to address the authorization requirements of the J2EE platform.

The J2EE Management API includes standard mappings of the model to the Common Information Model (CIM), to an SNMP Management Information Base (MIB), and to the Java object model through a server resident Enterprise JavaBeans (EJB) component, known as the J2EE Management EJB Component (MEJB). The MEJB provides interoperable remote access to the model from any standard J2EE application.

The J2EE platform includes JavaMail to support applications such as e-commerce websites. The JavaMail API provides the ability to send order confirmations and other user feedback.

J2EE supports two CORBA-compliant technologies: JavaIDL and RMI-IIOP. JavaIDL enables Java applications to interact with any CORBA-compliant enterprise system. RMI-IIOP technology combines the programming ease of the Java Remote Method Invocation API (RMI) with CORBA's Internet Inter-ORB Protocol (IIOP) for easier integration of J2EE applications with legacy applications.

While J2EE provides transaction support automatically, the Java Transaction API (JTA) provides a way for J2EE components and clients to manage their own transactions and for multiple components to participate in a single transaction.

The Java Message Service (JMS) API defines a standard mechanism for components to send and receive messages asynchronously, for fault-tolerant interaction.