Java EE Platform Overview

The Enterprise Server implements Java 2 Enterprise Edition (Java EE) 1.4 technology. The Java EE platform is a set of standard specifications that describe application components, APIs, and the runtime containers and services of an application server.

Java EE Applications

Java EE applications are made up of components such as JavaServer Pages (JSP), Java servlets, and Enterprise JavaBeans (EJB) modules. These components enable software developers to build large-scale, distributed applications. Developers package Java EE applications in Java Archive (JAR) files (similar to zip files), which can be distributed to production sites. Administrators install Java EE applications onto the Application Server by deploying Java EE JAR files onto one or more server instances (or clusters of instances).

The following figure illustrates the components of the Java EE platform discussed in the following sections.

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Containers

Each server instance includes two containers: web and EJB. A container is a runtime environment that provides services such as security and transaction management to Java EE components. Web components, such as Java Server Pages and servlets, run within the web container. Enterprise JavaBeans run within the EJB container.

Java EE Services

The Java EE platform provides services for applications, including:

• Naming - A naming and directory service binds objects to names. A Java EE application can locate an object by looking up its Java Naming and Directory Interface (JNDI) name.

• Security - The Java Authorization Contract for Containers (JACC) is a set of security contracts defined for the Java EE containers. Based on the client’s identity, containers can restrict access to the container’s resources and services.

• Transaction management - A transaction is an indivisible unit of work. For example, transferring funds between bank accounts is a transaction. A transaction management service ensures that a transaction is either completed, or is rolled back.

• Message Service - Applications hosted on separate systems can communicate with each other by exchanging messages using the Java™ Message Service (JMS). JMS is an integral part of the Java EE platform and simplifies the task of integrating heterogeneous enterprise applications.

Web Services

Clients can access a Java EE application as a remote web service in addition to accessing it through HTTP, RMI/IIOP, and JMS. Web services are implemented using the Java API for XML-based RPC (JAX-RPC). A Java EE application can also act as a client to web services, which would be typical in network applications.

Web Services Description Language (WSDL) is an XML format that describes web service interfaces. Web service consumers can dynamically parse a WSDL document to determine the operations a web service provides and how to execute them. The Application Server distributes web services interface descriptions using a registry that other applications can access through the Java API for XML Registries (JAXR).

Client Access

Clients can access Java EE applications in several ways. Browser clients access web applications using hypertext transfer protocol (HTTP). For secure communication, browsers use the HTTP secure (HTTPS) protocol that uses secure sockets layer (SSL).

Rich client applications running in the Application Client Container can directly lookup and access Enterprise JavaBeans using an Object Request Broker (ORB), Remote Method Invocation (RMI) and the internet inter-ORB protocol (IIOP), or IIOP/SSL (secure IIOP). They can access applications and web services using HTTP/HTTPS, JMS, and JAX-RPC. They can use JMS to send messages to and receive messages from applications and message-driven beans.

Clients that conform to the Web Services-Interoperability (WS-I) Basic Profile can access Java EE web services. WS-I is an integral part of the Java EE standard and defines interoperable web services. It enables clients written in any supporting language to access web services deployed to the Application Server.

The best access mechanism depends on the specific application and the anticipated volume of traffic. The Application Server supports separately configurable listeners for HTTP, HTTPS, JMS, IIOP, and IIOP/SSL. You can set up multiple listeners for each protocol for increased scalability and reliability.

Java EE applications can also act as clients of Java EE components such as Enterprise JavaBeans modules deployed on other servers, and can use any of these access mechanisms.

External Systems and Resources

On the Java EE platform, an external system is called a resource. For example, a database management system is a JDBC resource. Each resource is uniquely identified and by its Java Naming and Directory Interface (JNDI) name. Applications access external systems through the following APIs and components:

• Java Database Connectivity (JDBC) - A database management system (DBMS) provides facilities for storing, organizing, and retrieving data. Most business applications store data in relational databases, which applications access via JDBC. The Application Server includes the PointBase DBMS for use sample applications and application development and prototyping, though it is not suitable for deployment. The Application Server provides certified JDBC drivers for connecting to major relational databases. These drivers are suitable for deployment.

• Java Message Service - Messaging is a method of communication between software components or applications. A messaging client sends messages to, and receives messages from, any other client via a messaging provider that implements the Java Messaging Service (JMS) API. The Application Server includes a high-performance JMS broker, the Sun Java System Message Queue. The Platform Edition of Application Server includes the free Platform Edition of Message Queue. Sun GlassFishEnterprise Server includes Message Queue Enterprise Edition, which supports clustering and failover.

• Java EE Connectors - The Java EE Connector architecture enables integrating Java EE applications and existing Enterprise Information Systems (EIS). An application accesses an EIS through a portable Java EE component called a connector or resource adapter, analogous to using JDBC driver to access an RDBMS. Resource adapters are distributed as standalone Resource Adapter Archive (RAR) modules or included in Java EE application archives. As RARs, they are deployed like other Java EE components. The Application Server includes evaluation resource adapters that integrate with popular EIS.

• JavaMail - Through the JavaMail API, applications can connect to a Simple Mail Transport Protocol (SMTP) server to send and receive email.