264

.

Application 1

EIS A

Application 2

J2EE

Application

Server

Relational

database

Application 3

EIS B

Figure 6.4

J2EE Application Server as Integration Hub

Integration approaches vary, and often the situation dictates the best approach.

In some situations, the integration approach is fairly obvious. For example, when

a client requires a tightly coupled interaction with a relational database, clearly the

JDBC API is the design strategy to use. Similarly, another design strategy uses the

J2EE Connector architecture for data integration with non relational databases.

These two design strategies are particularly appropriate when the client requires

an API for connecting, querying, and updating a database with transactional

semantics. Other situations require you to combine technologies to meet the inte 

gration requirements. You might use connectors on top of a non relational data 

base, but then, based on the client requirements, you might add a Web service

layer on top of the connector. 

It is helpful to view the process of formulating an integration approach as

three separate tasks (each requiring a design and implementation phase):

  Decide on the integration layer, including where it should be located and what 

form it should take. With the J2EE platform, various integration layers are pos 

sible, including connectors, enterprise beans, JMS, and Web services. Remem 

ber that you want the integration layer to be such that other applications or 

systems can evolve easily. 

  Decide how to adapt each EIS to the integration layer.

  Decide how to write new applications against these integration layers.