by, 01-01-2012 at 03:25 PM (1144 Views)
Client tier presents Java, Web browser, or other applications like WAP phone, Applet etc. A request is sent to the Web server by the Client tier. Request is then forwarded to JSP or Servlet, or returns static content in case it is in Web server.
Presentation tier summarizes the presentation logic that is required for server clients. A JSP or Servlet present in presentation tier intercepts requests of clients, manages logons, or sessions. Business services are being accessed and finally a response is being constructed that is sent to client.
Business tier Business services are being provided by the Business tier. Business logic as well as business data is present in this tier. Business logics are centralized to this tier, in opposition to 2-tier where business logic has been scattered b/w back and front end. Having a centralized tier provides benefit as similar business logic provides support to the various client types, for example, WAP, browsers or some other stand alone application.
Integration tier To communicate with external resources like ERP systems, databases, messaging systems or legacy systems integration tier is used. JMS, JCA, JDBC are used by these tier components. For accessing resource tier, few proprietary middleware are used.
Resource tier is an external resource like ERP system, database or Mainframe system etc. Its basic responsibility is to store data. EIS (Enterprise Information System), or Data Tier are other names of this tier.