Use of XPath function in Message Template

[anuprai]

I am trying to form Json payload by reading xml payload in response. For this I am using AssignMessage policy with xpath function in Template.

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<AssignMessage async="false" continueOnError="false" enabled="true" name="AM-FormResponse">
    <DisplayName>AM-FormResponse</DisplayName>
    <Properties/>
    <AssignVariable>
        <Name>xpath</Name>
        <value>//return/code/text()</value>
    </AssignVariable>
    <AssignVariable>
        <Name>extracted_code</Name>
        <Template>{xpath(xpath,response)}</Template>
    </AssignVariable>
    <IgnoreUnresolvedVariables>true</IgnoreUnresolvedVariables>
    <AssignTo createNew="false" transport="http" type="response"/>
</AssignMessage>

While saving the proxy I am getting "Unknown string function : xpath" error.

I also tried using this function directly in Set Payload but there instead of value I am getting xpath in response.

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<AssignMessage async="false" continueOnError="false" enabled="true" name="AM-FormResponse">
    <DisplayName>AM-FormResponse</DisplayName>
    <Properties/>
    <Set>
        <Payload contentType="application/json">{
              "code": "{xpath('//return/code/text()',response.content)}"
            }
        </Payload>
    </Set>
    <IgnoreUnresolvedVariables>true</IgnoreUnresolvedVariables>
    <AssignTo createNew="false" transport="http" type="response"/>
</AssignMessage>

Output of this policy -

{
  "code": "{xpath('//return/code/text()',response.content)}"
}

I am trying this Apigee SaaS. How can I correct this?

[#2]

use extract variable policy to fetch the variables and then frame the json payload using assign message policy.

or

you can use xml-to-json policy and then format your json payload using assign message or javascript policy.

[anuprai]

Thanks Ajitav, I am able to form the message using EV and AM policies, just wanted to use xpath functions so that this can be done only using AM policy.

[dchiesa1]

I would try this :

<AssignMessage name="AM-FormResponse">
  <AssignVariable>
    <Name>my_path</Name>
    <Value>//return/code/text()</Value>
  </AssignVariable>

    <Set>
        <Payload contentType="application/json">{
              "code": "{xpath(my_xpath,response.content)}"
            }
        </Payload>
    </Set>
    <IgnoreUnresolvedVariables>true</IgnoreUnresolvedVariables>
    <AssignTo createNew="false" transport="http" type="response"/>
</AssignMessage>

[anuprai]

Thanks Dino for answering.

I tried this also but getting same error - "The revision is deployed, but traffic cannot flow. Unknown string function : xpath"

[dchiesa1]

That means you are on an older version of Apigee, which does not include the xpath function. If you upgrade, you'll get it. What version are you using?

[anuprai]

We are using Apigee SaaS.

[anuprai]

@Dino - Is this function not supported in Apigee Saas?

[dchiesa1]

It is being rolled out now. It is available in evaluation orgs for SaaS.

[debjitd18]

Hi @dchiesa1 sorry to restart this thread, not sure if there was one already existing if yes I can repost it. 
We are using Apigee X (1-11-0-apigee-7).

Use case - We are using a service callout to invoke a REST API. I am looking to capture the response field using Assign Message and was trying to use the jsonpath function but while deploying the proxy am getting a deployment error as - "reported error entities.UnknownStringFunction: "Unknown string function : jsonpath" ".
In the Assign Message I have this as below:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<AssignMessage continueOnError="false" enabled="true" name="AM-CaptureStatusCode">
<DisplayName>AM-CaptureStatusCode</DisplayName>
<Copy source="avScanResponse">
<Headers/>
<QueryParams/>
<FormParams/>
<Payload>true</Payload>
<Verb/>
<StatusCode/>
<ReasonPhrase/>
<Path/>
</Copy>
<AssignTo>avScanResponse</AssignTo>
<AssignVariable>
<Name>status_code</Name>
<Value/>
<Ref>avScanResponse.status.code</Ref>
</AssignVariable>
<AssignVariable>
<Name>rsp_status</Name>
<Value/>
<Template>{jsonpath($.avScanResponse,status)}</Template>
</AssignVariable>
<IgnoreUnresolvedVariables>true</IgnoreUnresolvedVariables>
<AssignTo createNew="false" transport="http" type="request"/>
</AssignMessage>

I was able to capture the status field using Extract Variables, but checking out option if it can be achieved through the Assign Message.

Sample Response from Service Callout:

    "status": "SUCCESS",
    "description": "Text Edited",
    "inputFilePath": null,
    "uploadedFilePath": null

Please let me know if anything is missing from my side will update accordingly.

Thanks and Regards,

Debjit

[dchiesa1]

ya, the string functions are case-sensitive. you want jsonPath, with an uppercase P.

[debjitd18]

Thank you @dchiesa1 it worked. It also proved I need a new set of spectacles. 

[dchiesa1]

😉

I'm glad you got it sorted out!