Using Petals to Implement a Service-oriented Architecture

The ESB is now capable of hosting JSR181 services exchanging SOAP messages.Deploying the previously created assembly is as easy as A-B-C: it is noting more than aregular component, and a simple copy/paste into the «install» directory does the trick:this action deploys the component on the ESB.But this is not sufficient to make it available as a regular SOAP service: a link between theSOAP component and the deployed service assembly must be created. The point is toexplain to the SOAP component to which component incoming SOAP requests must beforwarded to.Create a new «Petals Service Consumer», selecting «Communication Protocol» as keywords, and «SOAP // petals-bc-soap» as petals component (version «4.2»). The wizardnow asks which ESB service operation should be exposed through the SOAP protocol.Click on the «Select a service» link to open the selection wizard. In this wizard, select theport «HelloWorldPort» in the «Available Service» list, and then the operation to expose(i.e., «helloWorld»). The default project name is OK (i.e., «su-SOAP-HelloWorldconsume»),but change the «SOAP Service Name» to clearly identify its SOAP nature(e.g., «SOAPHelloWorld»). Ask PetalsStudio to generates the service assembly (rightclick,«Petals», «Fast export to Petals»), and deploy the generated zip archive on the ESBusing the usual copy/paste auto-deploy mechanism.The developed web service is now executed by the JSR-181 Service Engine, and exposedthrough the SOAP Binding Component. You can list the services available through theSOAP BC on the dedicated web page: http://localhost:8084/petals/services/listServices.The service can be accessed through a standard SOAP client (e.g., soapUI 1 ).Fig 4. Using soapUI to interact with the service1 http://sourceforge.net/projects/soapui/files/4

Create and Deploy a BPEL processThe Business Process Execution Language (BPEL) supports the description of servicecomposition (as «business processes») in a high level and standardised formalism.Hosting a BPEL artefact in the Petals ESB follows the same principles than the previousweb service deployment: (i) deploy the associated service engine, (ii) implement theprocess, (iii) deploy it on the ESB and finally (iv) expose it to the external world though theSOAP-BC component.To deploy the BPEL service engine, copy/paste the «petals-se-bpel-1.1.0.zip»component into the «install» directory.To implement a BPEL process, simply create a new «Petals Service Provider» inthe PetalsStudio IDE. The «BPEL // petals-se-bpel» component is available under the«Service Composition» key word. Use «HelloWorldProcess» name, in the «http://sandbox.soa.polytech.unice.fr» namespace. In this tutorial, we’ll create asynchronous process. The wizard generates a process skeleton, which basically containsthree activities: (i) the reception of a triggering message (receive), (ii) the sending of asynchronous response to the caller (reply), and (iii) and empty activity in between. As theservice is useless «as is», open the source of the «HelloWorldProcess.bpel» file, andreplace the «empty» activity by the following code:Hello, World!This code declares an assign activity that first initialise the output message with agreetings.To deploy the process, ask Petals Studio to «fast export toPetals», and then copy/paste the generated zip archive inthe «install» directory of the ESB.Then, the service is not yet accessible for external callers:a SOAP binding must be defined and then deployed.Create a new «Petals Service Consumer», using«SOAP // petals-bc-soap» component. With the «select aservice» wizard, selects the «HelloWorldProcessPort»,and the «process» operation. Do not forget to prefix bySOAP the «SOAP Service Name».To deploy the binding, ask PetalsStudio to «fast export toPetals», and then copy/paste the generated zip archive inthe «install» directory of the ESB. The process becomesavailable to the outside world, and is listed in the http://localhost:8084/petals/services/listServices page.Fig 5. BPEL graph. display5

Fig 6. Using soapUI to interact with the process6