1.2 WAS

WAS provides the environment to run your Web-enabled e-business applications. An appserver functions as Web middleware or a middle tier in a three-tier e-business environment. The first tier is the HTTP server that handles requests from the browser client. The third tier is the business database (for example, DB2 UDB for iSeries) and the business logic (for example, traditional business applications, such as order processing). The middle tier is WAS, which provides a framework for a consistent and architected link between the HTTP requests and the business data and logic.

WAS is available on a wide range of platforms and in multiple packages to meet specific business needs. It also serves as the base for other WebSphere products, such as WebSphere Enterprise Service Bus and WebSphere Process Server, by providing the appserver that is required to run these specialized applications.

Figure 1-1 illustrates a product overview of WAS.

Figure 1-1 WAS product overview

The appserver is the key component of WAS, providing the run time environment for applications that conform to the J2EE 1.2, 1.3, and 1.4 specifications. Clients access these applications through standard interfaces and APIs. The applications, in turn, have access to a wide variety of external sources, such as existing systems, databases, Web services, and messaging resources that can be used to process the client requests. V6.1 extends the appserver to allow it to run JSR 168 compliant portlets and Session Initiation Protocol (SIP) applications written to the JSR 116 specification.

With the Base and Express packages, you are limited to single appserver environments. The ND package allows you to extend this environment to include multiple appservers that are administered from a single point of control and can be clustered to provide scalability and high availability environments.

WAS supports asynchronous messaging through the use of a JMS provider and its related messaging system. WAS includes a fully integrated JMS 1.1 provider called the default messaging provider. This messaging provider complements and extends WebSphere MQ and appserver. It is suitable for messaging among appservers and for providing messaging capability between WAS and an existing WebSphere MQ backbone.

WAS provides authentication and authorization capabilities to secure administrative functions and applications. Your choice of user registries include the operating system user registry, an LDAP registry (for example, TivoliŽ Directory Server), custom registries, file-based registries, or federated repositories. In addition to the default authentication and authorization capabilities, you have the option of using an external Java Authorization Contract for Containers (JACC) compliant authorization provider for application security. The IBM Tivoli Access Manager client embedded in WAS is JACC-compliant and can be used to secure your WAS-managed resources. This client technology is designed to be used with the Tivoli Access Manager Server (shipped with ND).

WAS works with a Web server (such as the IBM HTTP Server) to route requests from browsers to the applications that run in WAS. Web server plug-ins are provided for installation with supported Web browsers. The plug-ins direct requests to the appropriate appserver and perform workload balancing among servers in a cluster.

WAS ND includes the Caching Proxy and Load Balancer components of Edge Component for use in highly available, high volume environments. Using these components can reduce Web server congestion, increase content availability, and improve Web server performance.