SOA

SCDL is used to describe SCA elements such as modules, references, imports, and exports. You will see examples of these throughout the series. SCDL definitions are organized across several files. For example, we store the SCDL for the interface and implementation in a file called CreditApproval.component. References can be included in the CreditApproval.component file (in-line) or in a separate sca.references file located in the Module root. Any standalone reference will be placed in the sca.references file, shown below. As we mentioned, standalone references can be used by non-SCA artifacts (JSP) within the same SCA module to invoke the SCA component.

Listing 6:

<?xml version="1.0" encoding="UTF-8"?>
<scdl:references xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:java="http://www.ibm.com/xmlns/prod/websphere/scdl/java/6.0.0"
xmlns:scdl="http://www.ibm.com/xmlns/prod/websphere/scdl/6.0.0">
  <reference name="CreditRequestPartner">
    <interface xsi:type="java:JavaInterface"
	interface="approval.credit.credit.request.CreditRequest">
      <method name="calulateCreditScore"/>
    </interface>
    <wire target="CreditApproval"/>
  </reference>
</scdl:references>

In our example, a third file we will define is the sca.module. This SCDL file will contain the definition for the module:

Listing 7:

<?xml version="1.0" encoding="UTF-8"?>
<scdl:module xmlns:scdl="http://www.ibm.com/xmlns/prod/websphere/scdl/6.0.0"
name="CreditApproval"/>

Although we defined a WSDL interface for our component, notice that we are able to add another Java interface to the standalone reference and wire it to our target component. In this manner, Java clients can invoke SCA components using a simple POJI. WebSphere Integration Developer will provide the option to translate the call between the Java and WSDL interface. You will see an example of this shortly when you create your first SCA component.

We will see examples of how SCDL defines other SCA artifacts, such as service references, imports, and exports, throughout this article series. The naming conventions for the SCDL files above are used by WebSphere Integration Developer, and were actually by using WebSphere Integration Developer. In our example, you will use WebSphere Integration Developer when building your first SCA component. However, SCA applications can also be built using a notepad process as well.

WebSphere Integration Developer and WebSphere Process ServerIn this article, you will use WebSphere Integration Developer and WebSphere Process Server to build and run your SCA components.

WebSphere Integration Developer is used to develop applications that run on WebSphere Process Server V6. WebSphere Integration Developer, based on the Eclipse 3.0 platform, delivers role-based development for integration projects. You can use WebSphere Integration Developer and IBM WebSphere Business Modeler V6 together with IBM Rational® Application Developer V6 or IBM Rational Software Architect V6 as an integration development platform. J2EE developers, business analysts, or integration developers can use the tooling perspective based on their unique roles, so that each developer can focus on the editors and tools needed for those roles, thereby maximizing productivity.

WebSphere Process Server is a comprehensive integration platform which is based on WebSphere Application Server V6. WebSphere Process Server is used to execute component-based business integration applications in a service-oriented architecture. Because it is based on J2EE 1.4 infrastructure and platform services provided by WebSphere Application Server, WebSphere Process Server includes capabilities such as business process automation.

See Resources for more details on both WebSphere Integration Developer and WebSphere Process Server.

Build your first SCA projectYou are now ready to build your first SCA project. In this example, you will build a simple credit approval component. The component will take in a data object with an ID and name, and then return another data object containing a credit score and credit limit. Download the zip file included with this article and extract it to your hard drive. The instructions assume you extract the zip file to your C: drive.

WebSphere Integration Developer V6.0 is a flexible development environment that provides tools and wizards for developing SCA applications from the bottom-up or from the top-down.

For the creation of the credit approval service, we will explore the aspects of top-down development. The general high level steps in our top-down development process are:

1. Create the SCA module.
2. Create the business objects.
3. Define the service interface.
4. Generate the component and provide an implementation.
5. Unit test the SCA component.
6. Provide a standalone reference.
7. Test the service using a simple JSP client.

Create an SCA moduleFirst, you need to create an SCA module. As stated earlier, an SCA module is the packaging construct of SCA components.

1. Open WebSphere Integration Developer to a blank workspace. (Figure 9)
2. Close the Welcome screen.
3. Next you will create a new module.
   a. Your WebSphere Integration Developer workbench should be open to the Business Integration perspective. Find the Business Integration view.
   b. Right-click inside the Business Integration view and select New => Module. (Figure 10)
   c. The New Module wizard should display (Figure 11). Name the Module CreditApprovalSCAModule.
   d. You should now have a new project displaying in the Business Integration view. SCA modules are described as a SCDL file. The Business Integration view shows you a logical view of your SCA module. You can open the Physical Resource view to see the physical resources contained in the SCA module, as previously discussed. The SCDL for the SCA module is contained in the file called sca.module. If you open the file with a text editor, you should see something like this:

Listing 8:

<?xml version="1.0" encoding="UTF-8"?>
<scdl:module xmlns:scdl="http://www.ibm.com/xmlns/prod/websphere/scdl/6.0.0"
name="CreditApprovalSCAModule"/>

Create the business objects. There is no predefined sequence of tasks for creating interfaces or business objects; you could have just as easily have created the business objects when creating the interface. Here we chose to create business objects from the Business Integration view.

When creating a business object, you are actually creating an XML schema. Business objects are stored as standard XML schema. Applications can access the data using the SDO programming model and XPath.

The Business Object Editor enables us to create the business object definitions that will be used by the credit approval service. There are two business objects that are needed for our service.

CreditApplication: Contains the information about the credit applicant necessary to calculate a credit rating. The credit application business object (CreditApplication) consists of three attributes:

• Customer Id: unique identifier of the customer
• First Name: customer's first name
• Last Name: customer's last name

CreditRating: Contains credit rating information such as credit score and credit limit. The credit rating business object (CreditRating) consists of three attributes:

• Credit Score: customer's credit score based on prior history
• Credit Limit: total amount that the customer may owe.

1.  We begin by creating our Request business object, which will be used as an input parameter to our SCA component.
a. Make sure that the CreditApprovalSCAModule is expanded. Right click on Data Types and select New => Business Object. (Figure 12)
b. Name your business object CreditApplication as shown in Figure 13.
c. The business object should open in the Business Object Editor. You should now have the CreditApplication under the Data Types menu. (Figure 14)

2.  We will now define the attributes of the CreditApplication business object.
a. You can add an attribute by selecting the Add Attribute icon as shown in Figure 15.
b. Enter customerId as the attribute name and accept the default String type. (To change the type, you could just select the type field and select it from the drop-down box. You will do this for the response object.)

Figure 16. Define attribute
c. Add two more String attributes and name them firstName and lastName. Both of them should be of type string as shown below.