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). 

1.6.3

Loosely Coupled Applications

RMI/IIOP

JSP

Session EJB

RMI/IIOP

HTTP/HTML/XML

RMI/IIOP

RMI/IIOP

Session EJB

JSP

intra/inter/extranet

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

Overview

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