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 
the Java
2 Platform Enterprise Edition (J2EE). 
Loosely Coupled Applications
Session EJB
Session EJB
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.
Chapter 1

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