WebSphere Application Server is a platform on which Java-based business applications run. WebSphere Application Server Is an implementation of the Java 2 Enterprise Edition(J2ee) Specification.
WebSphere Application Server provides services (database connectivity, threading, workload management, and so forth) that can be used by the business applications. The main element is the application server, a java process that encapsulates many services, including the containers, where business logic executes. If you are familiar with J2EE, you will recognize the Web Container and the EJB container. The Web container executes Servlets and JavaServer Pages(JSPs), both of which are java classes that generate markup to be viewed by a Web browser. Traffic into and out of the Web Container travels through the embedded HTTP Server. While Servlets and JSPs can act independently, they most commonly make calls to Enterprise Java Beans (EJBs) to executes business logic or access data. EJBs, which run in the EJB container, are easily reusable java classes. They most commonly communicate with a relational database or other external source of application data, either returning that data to the Web container or making changes to the data on behalf of the servlet or JSP.
The JMS messaging engine is built into the application server. This is a pure-java messaging engine. JMS destinations, known as queues and topics provide asynchronous messaging services to the code running inside the containers, JMS will be covered in more depth later in this course.
As you will see in more detail later on, the web services engine enables application components to be exposed as web services, which can be accessed using Simple Object Access Protocol (SOAP).
Several other services run within the application server, including the dynamic cache, data replication, security, and others. These will be covered later in this course.
There are also some important components outside of the application server process.
WebSphere Application Server also provides a plug-in for HTTP servers that determines what HTTP traffic is intended to be handled by WebSphere, and routes the requests to the appropriate server. The plug-in is also a critical player in workload management of HTTP requests, as it can distribute the load to multiple application server, as well as steer traffic away from unavailable servers. It too roads its configuration from a special XML file.
One of the servervices provided within the application server is the admin service. This service allows for the ability to configure the application server. This files necessary for configuration are stored outside of the actual application server in a set of XML configuration files. There is an application that runs within the Web application-the admin console.