In this model the application is composed of (n>=3) tiers, where the middle tier, the JSP,
interacts with the back end resources via an Enterprise JavaBeans component. The Enterprise
JavaBeans server and the EJB provide managed access to resources thus addressing the
performance issues. An EJB server will also support transactions and access to underlying
security mechanisms to simplify programming. This is the programming model supported by
2 Platform Enterprise Edition (J2EE).
Loosely Coupled Applications
In this model we have two loosely coupled applications (either on the same Intranet, or over
an Extranet or the Internet). These applications may be peers, or act as client or server for the
other. A common example of this is supply chain applications between vendor enterprises. In
such situations it is important that each participant be isolated from changes in the
implementation of it's dependents. In order to achieve this loose coupling the applications do
not communicate using a fine grain imperative interface contract like those provided for by
RMI/IIOP or Java IDL. The applications communicate with each other via HTTP, using
either HTML or XML to/from a JSP page.