Chapter 6 

265

Keep in mind that an important reason for using an integration layer is the ser 

vices it provides for distribution. Usually, EISs are located on different physical

machines, or they may be run as separate processes. To integrate these EISs, you

need to use a distributed technology. J2EE application servers are an excellent

choice for integration because they can handle multiple protocols for distributed

computing: Internet Inter ORB Protocol (IIOP), messaging, HTTP and Web ser 

vices. In addition, J2EE application servers can handle native EIS protocols

through connectors. These native protocols include proprietary protocols used by

ERP and database vendors, among others. 

Figure 6.5 shows the  that are possible with the

J2EE technologies. 

Note:

 This figure uses dashed lines to represent asynchronous calls, such as

sending a JMS message. The solid lines show synchronous calls, which are made

either through EJB or Web service APIs. The three applications, which are shown

on the left side of the diagram, are new EAI applications that you might be writ 

ing. The right side of the diagram shows some of the existing EIS systems that

need to be integrated with the EAI applications. 

.

Connector as integration layer

Application 1

EIS A

B

MD

ector

EJB/JMS as

nn

Application 2

integration layer

J2EE

EJB

Co

Application

ice

Server

rv

Web Se

MP/C

Relational

CB

database

Application 3

Web services

JD

MDB

as integration

layer

EIS B

Figure 6.5

EIS