In this blog we will discuss how we can create BPEL using multiple operations in WSDL
Scenario: We will take the example of four basic mathematic binary operations (addition, subtraction, multiplication, division) to demonstrate this. Our task is to build a web service that has four different operations. The condition however we have is to do that only one BPEL Process. We cannot have four BPEL process implementing four different web services.
Step wise discription provided to implement the process
Step 1: create an Empty BPEL process project ‘MultipleWSDLoperations’ (Define Interface later template )
Step 2: Add a new schema MAthCalculations.xsd to the BPEL process project. In this example I used simple types for input and output. You may have complex types depending on your business use case. Also as all operations are binary and all of them share the same input and output signature, Request and Response elements are reused in this example. You may have different Request Response element types/structure. You can declare them in the same schema file.
Step 3: create my WSDL with the required Operations in it. My WSDL uses the schema created in the previous step
<?xml version="1.0" encoding="UTF-8" ?>
<definitions targetNamespace="tns:MAthCalculationWSDL"
xmlns="http://schemas.xmlsoap.org/wsdl/"
xmlns:tns="tns:MAthCalculationWSDL"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
xmlns:mime="http://schemas.xmlsoap.org/wsdl/mime/"
xmlns:ns2="http://www.example.org"
xmlns:soap12="http://schemas.xmlsoap.org/wsdl/soap12/">
<types>
<xsd:schema targetNamespace="tns:MAthCalculationWSDL/types"
elementFormDefault="qualified">
<xsd:import namespace="http://www.example.org" schemaLocation="xsd/MathCalculations.xsd" />
</xsd:schema>
</types>
<message name="MathoperationrequestMessage">
<part name="MathoperationInputmessage" element="ns2:Inputvales"/>
</message>
<message name="MathoperationresponseMessage">
<part name="MathoperationOutputmessage" element="ns2:Outputvales"/>
</message>
<portType name="MathOperation">
<operation name="add">
<input message="tns:MathoperationrequestMessage"/>
<output message="tns:MathoperationresponseMessage"/>
</operation>
<operation name="Substract">
<input message="tns:MathoperationrequestMessage"/>
<output message="tns:MathoperationresponseMessage"/>
</operation>
<operation name="Multiply">
<input message="tns:MathoperationrequestMessage"/>
<output message="tns:MathoperationresponseMessage"/>
</operation>
<operation name="Divide">
<input message="tns:MathoperationrequestMessage"/>
<output message="tns:MathoperationresponseMessage"/>
</operation>
</portType>
</definitions>
Step 4: add a partner link using the WSDL above. Name this ‘client’ with Role as ‘Provider’. This action imports the WSDL and adds a partnerLinType tag to the imported WSDL.
<plnk:partnerLinkType name="MathOperation_PL">
<plnk:role name="MathOperation_Role">
<plnk:portType name="tns:MathOperation"/>
</plnk:role>
</plnk:partnerLinkType>
and also Namespace as : xmlns:plnk="http://schemas.xmlsoap.org/ws/2003/05/partner-link/"
During this step also create two global variables ‘inputVariable’ and ‘outputVariable’ for the Request and Response data using the Project WSDL.
You can directly add sourcecode in Bpel
<variables>
<!-- Reference to the message passed as input during initiation -->
<variable name="inputVariable"
messageType="ns1:MathoperationrequestMessage"/>
<!-- Reference to the message that will be sent back to the requester during callback -->
<variable name="outputVariable"
messageType="ns1:MathoperationresponseMessage"/>
</variables>
note: the code above creates two global variables namely inputVariable,outputVariable
Step 5: add a pick activity to the empty BPEL process,. This activity waits for the occurrence of one event in a set of events and performs the activity associated with that event. In our case an event translates to a web service operation. If more than one of the events occurs, then the selection of the activity to perform depends on which event occurred first. If the events occur nearly simultaneously, there is a race and the choice of activity to be performed is dependent on both timing and implementation. As our implementation is going to be state-less atomic services, we may not have a racing condition. Coming back to the pick activity The pick activity provides two branches, each one with a condition. When you double-click the pick icon, the pick activity shown in figure below, appears and displays these two branches: onMessage (on the left) and onAlarm (on the right). The onMessage branch contains the code for receiving a reply, for example, from a loan service. The onAlarm branch contains the code for a timeout, for example, after one minute. Whichever branch completes first is executed; the other branch is not. The branch that has its condition satisfied first is executed.
Step 6: delete the alarm branch (from BPEL Source) as we will not be using it. Also add 3 more onMessage branches to implement all the four operations in the WSDL.
Create a webservice with the created "MAthCalculationWSDL" above
Step 7: for each of the onMessage branch, associate the WSDL operation as shown below.
Create 4 variables namely
OnMessage_add_InputVariable
OnMessage_Substract_InputVariable
OnMessage_Multiply_InputVariable
OnMessage_Divide_InputVariable
with respective Operations
add
Substratct
Multiply
Divide
Now you have a BPEL process that can branch based on the operations invoked by the client.
Step 8: implement the mathematical operations under each branch and provide a synchronous response to the client. Add a simple assign step followed by reply activities to achieve this.
For each Assign assign activities I use a simple copy operation to perform the mathematical operation.
Same as for 4 Assigns add simple copy operations to define the Mathematical fuction we implement
Step 9: In each of the reply activities assign the output variable and partner link
Deploy and test the service.
By-DeepthiReddy
No comments:
Post a Comment