Re: When we need to initialize a variable

[Bill McCusker]

Hi,

Variables need to be initialized before they are assigned from or when 
assigned to using a query or an expression or if they are used as to 
input to an invoke or in conditional expressions. If you are just 
assigning directly to a variable's message part with no query then no 
initialization is needed. Thats why the second example needs no 
initialization.

Bill McCusker

phanlesang wrote:
Hi Everyone!
I'm getting confused about when we need to initialize a variable in BPEL 2.0
though BPEL 2.0 standard says that every variable must be initialized before
using.
For example:
In the HelloBPELProcess example, I see the variable output is initialized:

<bpel:assign validate="no" name="createResponse">
            <bpel:copy>
                <bpel:from>
                    <bpel:literal
xml:space="preserve"><tns:HelloBPELProcessResponse
xmlns:tns="http://www.se.uni-hannover.de/soa08/tutorial/HelloBPELProcess";
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";>
  <tns:result></tns:result>
</tns:HelloBPELProcessResponse>
</bpel:literal>
                </bpel:from>
                <bpel:to variable="output" part="payload"></bpel:to>
            </bpel:copy>
            <bpel:copy>
                <bpel:from part="payload" variable="input">
                    <bpel:query
queryLanguage="urn:oasis:names:tc:wsbpel:2.0:sublang:xpath1.0"><![CDATA[tns:input]]></bpel:query>
                </bpel:from>
                <bpel:to part="payload" variable="output">
                    <bpel:query
queryLanguage="urn:oasis:names:tc:wsbpel:2.0:sublang:xpath1.0"><![CDATA[tns:result]]></bpel:query>
                </bpel:to>
            </bpel:copy>
        </bpel:assign>

But in the SimpleInvokeProcess process, the variable output is not
initialized:

<bpel:assign validate="no" name="PrepareRandomHelloRequest">
            <bpel:copy>
                <bpel:from>
                    <bpel:literal xml:space="preserve"><impl:sayHello
xmlns:impl="http://randomHelloService.tutorial.soa08.se.unihannover.de";
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";>
  <impl:withSpace></impl:withSpace>
</impl:sayHello>
</bpel:literal>
                </bpel:from>
                <bpel:to variable="RandomHelloRequest"
part="parameters"></bpel:to>
            </bpel:copy>
            <bpel:copy>
                <bpel:from>
                    <bpel:literal xml:space="preserve">true</bpel:literal>
                </bpel:from>
                <bpel:to part="parameters" variable="RandomHelloRequest">
                    <bpel:query
queryLanguage="urn:oasis:names:tc:wsbpel:2.0:sublang:xpath1.0"><![CDATA[ns1:withSpace]]></bpel:query>
                </bpel:to>
            </bpel:copy>
        </bpel:assign>
        <bpel:invoke name="GetGreeting" partnerLink="RandomHelloPL"
operation="sayHello" portType="ns1:RandomHelloService"
inputVariable="RandomHelloRequest"
outputVariable="RandomHelloResponse"></bpel:invoke>
        <bpel:assign validate="no" name="PrepareOutput">
            <bpel:copy>
                <bpel:from xmlns:http="urn:http:namesapce">
                   
<![CDATA[concat(bpel:getVariableData('RandomHelloResponse', 'parameters',
'/'), bpel:getVariableData('input', 'payload', '/'))]]>
                </bpel:from>
                <bpel:to variable="output" part="payload"></bpel:to>
            </bpel:copy>
        </bpel:assign> 

Thanks for any help!

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