An application server is a Java™ Virtual Machine (JVM) that runs user
applications. The application server collaborates with the Web server to return
a dynamic, customized response to a client request. The client request can
consist of servlets, JavaServer Pages (JSP) files, and enterprise beans, and
their supporting classes.
For example, a user at a Web browser visits a company Web site:
- The user requests access to data in a database.
- The user request flows to the Web server.
- The Web server determines that the request involves an application containing
resources not handled directly by the Web server (such as servlets). It forwards
the request to one of its application servers on which the application is
running.
- The invoked application then processes the user request. For example:
- An application servlet prepares the user request for processing by an
enterprise bean that performs the database access.
- The application produces a dynamic Web page containing the results of
the user query.
- The application server collaborates with the Web server to return the
results to the user at the Web browser.
When you install the product, a default application server, named server1,
is automatically created. You can use the administrative console to manage
this server.
You can use the administrative console or wsadmin
commands to create additional application servers that can either be separately
configured processes or nearly identical clones. As with server1, you can
use the administrative console to mange these additional servers.
New feature: You can improve system performance
if you configure some of your application servers, such that each of their
components are dynamically started as they are needed, instead of letting
all of these components automatically start when the server starts. Selecting
this option can improve server startup time, and reduce the memory footprint.
Starting components as they are needed is most effective if all of the applications
that are deployed on the application server are of the same type. For example,
using this option works better if all of your applications are Web applications
that use servlets, and JavaServer Pages (JSP). This option works less effectively
if your applications use servlets, JSPs and Enterprise JavaBeans™ (EJB).
newfeat
You can also perform the following tasks to enhance the operation of an
application server:
- Configure transport chains to provide networking
services to such functions as the service integration bus component of IBM® service
integration technologies, WebSphere® Secure Caching Proxy, and the high availability
manager core group bridge service.
- Add an interface to an application server to define a hook point that
runs when the server starts and shuts down.
- Define command-line information that passes to a server when it starts
or initializes.
- Tune the application server.
- Enhance the performance of the application server JVM.
- Configure an Object Request Broker (ORB) for RMI/IIOP communication.
Asynchronous messaging
The product supports asynchronous
messaging based on the Java Message Service (JMS) of a JMS provider that conforms
to the JMS specification Version 1.1.
The JMS functions of the default
message service that is provided with the product are served by one or more
messaging engines (in a service integration bus) that runs within application
servers.
Version 5.1 nodes can exist in a
deployment manager cell. If a Version 5.1 node does exist in a deployment
manager cell, and is configured to use Version 5.1 default messaging, only
one JMS server can reside on that node.
Generic Servers
A generic server is a server that
is managed in the WebSphere administrative domain, although it is not a server
that is supplied by the product. The generic server can be any server or process
that is necessary to support the product environment.