- Application server
In n-tier architecture an application server is a
serverthat hosts an APIto expose Business Logicand Business Processesfor use by other applications [ [http://mediaproducts.gartner.com/reprints/microsoft/vol3/article2/article2.html Magic Quadrant for Enterprise Application Servers, 2Q08 ] ] . The term can refer to:
# The Services that are made available by the server
Computer Hardwareon which the Services are deployed
Software frameworkused to host the Services such as JBoss application serveror Oracle Application Server
Java application servers
Following the success of the
Java platform, the term "application server" sometimes refers to a J2EEor Java EE 5 application server. Among the better known Java Enterprise Edition application servers are WebLogic Server (BEA), JBoss( Red Hat), WebSphere Application Server and WebSphere Application Server Community Edition ( IBM), JRun( Adobe), Apache Geronimo( Apache Software Foundation), Oracle OC4J ( Oracle Corporation), Sun Java System Application Server( Sun Microsystems), SAP Netweaver AS (SAP), and Glassfish Application Server(based on Sun Java System Application Server). JOnAS application serverwas the first open source application server to have achieved official compliance with the Java Enterprise Specification. BEA delivered the first Java EE 5 certified application server followed by Sun Microsystems' reference implementation GlassFish.
The Web modules are
servletsand JavaServer Pages, and business logic is built into Enterprise JavaBeans (EJB-3 and later). The Hibernateproject offers an EJB-3 container implementation for the JBossApplication server. Tomcat from Apache and JOnAS from ObjectWeb are typical of containers into which these modules can be put.
A Java Server Page (JSP) is a servlet from Java that executes in a Web container—the Java equivalent of
CGI scripts. JSPs are a way to create HTMLpages by embedding references to the server logic within the page. HTML coders and Java programmers can work side by side by referencing each other's code from within their own. JavaBeansare the independent class components of the Java architecture from Sun Microsystems.
The application servers mentioned above mainly serve Web applications. Some application servers target networks other than the Web:
Session Initiation Protocolservers, for instance, target telephony networks.
Microsoft's contribution to application servers is the
.NET Framework. This technology includes the Windows Communication Foundation, .NET Remoting, Microsoft Message Queuing, ADO.NET, and Internet Information Services.
Open source application servers are available from other vendors. Examples include
Appaserver, Base4 and Zope.
Non-Java offerings have no formal interoperability specifications, like the Java Specification Request. As a result, interoperability between non-Java products is poor compared to that of Java EE based products. To address these shortcomings, specifications for
enterprise application integrationand service-oriented architecturewere designed to connect the many different products. These specifications include Business Application Programming Interface, Web Services Interoperability, and Java EE Connector Architecture.
Advantages of application servers
; Data and code integrity : By centralizing business logic on an individual or small number of server machines, updates and upgrades to the application for all users can be guaranteed. There is no risk of old versions of the application accessing or manipulating data in an older, incompatible manner.; Centralized configuration : Changes to the application configuration, such as a move of database server, or system settings, can be done centrally.; Security : A central point through which access to data and portions of the application itself can be managed is considered a security benefit, devolving responsibility for authentication away from the potentially insecure client layer without exposing the database layer.; Performance : By limiting the network traffic to performance tier traffic, it is perceived that the client-server model improves the performance of large applications in heavy usage environments.;
Total Cost of Ownership(TCO) : In combination, the benefits above are considered to represent a cost saving to a company when developing enterprise applications. In practice, however, the technical challenges of writing software that conforms to that paradigm combined with the need for software distributionto distribute client code somewhat negate these benefits.
; Transaction Support : A transaction is a unit of activity, in which many updates to resources (that can be on the same or distributed data sources) can be made atomic (as an indivisible unit of work). End users can benefit by a system wide standard behaviour and less time to develop (and cost) as the server does a lot of the hard programming. Developers can focus on business logic.
Comparison of application serversSee this article for a list of web application servers listed by programming language.
* [http://www.jboss-server.com/ Jboss server tutorials]
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