Managing Information Access to an Enterprise Information System Using J2EE and Services Oriented Architecture

174 Managing Information Access to an EIS Using J2EE and Services Oriented Architecture

an so on. All these qualities are discussed in 7.5, “Quality of service for Web

services” on page 180.

The topmost layer in the stack is the

Business Process layer (also known as

Service Orchestration). This layer is implemented using Business Process

Execution Language for Web Services (BPEL4WS0 or BPEL for short. It adds

the capability to compose many services into a workflow to deliver a new

complex business service. Although it is logically positioned as the last layer, it is

independent of the Quality of Service layer. So, we can run a BPEL process even

without security, reliability, coordination, and transaction.

7.4 Using Web services to integrate EIS

This section shows how to make the EIS accessible through the Web services

technology using a build to integrate approach. We used WebSphere Studio

Application Developer Integration Edition to make the EIS accessible with a Web

service interface.

7.4.1 WebSphere Studio Application Developer Integration Edition

WebSphere Studio Application Developer Integration Edition V5.1.1, at its core,

provides easy-to-use tools for creating reusable services out of a variety of

back-end systems and for choreographing the interactions between those

services using BPEL4WS.

WebSphere Studio Application Developer Integration Edition provides a toolbox

for discovering, creating, and publishing Web services that are created from

JavaBeans, DADX files, Enterprise JavaBeans, and URLs. You can also use

Web services tools to create a skeleton JavaBean and a sample application from

a WSDL document.

A Web service can be implemented from:

򐂰 An existing application (bottom-up), transforming an existing application into a

Web service that includes the generation of service wrappers to expose the

business functionality.

򐂰 An existing service definition (top-down), generating a new application

skeleton from a service definition (WSDL).

WebSphere Studio Application Developer Integration Edition extends the Web

service capabilities of WebSphere Studio Application Developer with a more

service-oriented approach.

Chapter 7. Using Web services 175

Business services

At the heart of the Integration Edition programming model are business services,

which are used to consistently model different kinds of service providers.

Services are the business functions of your enterprise, or of your business

partners. You can use the integration tools to develop various types of services,

including Web services, processes, EIS (J2EE Connector) services, JMS

services, and so on. WSDL is used as the model for describing any kind of

service.

Business processes

A business process is a service implementation that represents a part of your

business operations. It can be totally automated or may require human

interaction at certain points. WebSphere Studio Application Developer

Integration Edition provides a model that allows you to implement these

processes in a very efficient graphical way.

The following sections discuss how to expose the developed process as a Web

service, how to invoke a Web service inside the process, and what are the main

related issues.

See 7.6, “Further information” on page 195 for reference information about

WebSphere Studio Application Developer Integration Edition and how to develop

Web services.

7.4.2 Expose the process as a Web service

To expose a process as a Web service is a simple activity. The business process

engine of WebSphere Business Integration Server Foundation is based on the

BPEL4WS language that uses the Web services concept.

BPEL states that any interface from the process and to the external world is a

Web service and is physically described by a WSDL file. As a consequence, you

need to establish only the details of the communication, which is called in Web

services jargon,

defining the binding.

The binding definition for a process is done during the last development phase,

which is

Generate Deploy Code. The deploy wizard of WebSphere Studio

Application Developer Integration Edition shows all the interfaces of the process.

The Interfaces for Partners section contains all the interfaces that the process

exposes to its clients. For each interface (PortType), it is possible to select which

binding to make available. For an example, see Figure 7-4 on page 176.