Assignmessage policy is not appending the query string parameters to the service callout url

Google Cloud Apigee
1

My scenario is calling a service B with some parameters that are passed in the request query string. I have to introduce a service callout in the preflow to call service A with those parameters set in AssignMessagePolicy, get the response of A and extract the required fields using ExtractVariables policy and pass them to service B. I have done with what all required but the flow fails as service callout to service A is not having query string parameters in the url though they were set in ASsignMessagePolicy.

AssignMessagePolicy to service A:

API V1 Request InitializeAPIRequest {request.queryparam.apiKey} {request.queryparam.applicationId} {request.queryparam.twoDigitISOLanguageCode} {request.queryparam.twoDigitISOCountryCode} GET apiKey request.queryparam.apiKey applicationId request.queryparam.applicationId twoDigitISOLanguageCode request.queryparam.twoDigitISOLanguageCode twoDigitISOCountryCode request.queryparam.twoDigitISOCountryCode

ServiceCallout:

300000 InitializeAPIResponse http://api.art.com/ECommerceAPI.svc/jsonp/InitializeAPI

ExtractVariablesPolicy:

InitializeAPIResponse intializeresponse $.d.CustomerZoneID $.d.IsoCurrencyCode

AssignMessagePolicyto service B:

{intializeresponse.CustomerZoneID}

Proxy Endpoints:

PreFlow:

API-V1-Request API-V1-InitializeAPI API-V1-Response Products-V2-Request request.verb equals “GET” and proxy.pathsuffix MatchesPath “/Products/*” ValidateOAuth

2

Hi Sagar,

I’ve sent my query param is the service callout policy itself in some of my samples, and that worked for me in the past:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ServiceCallout enabled="true" continueOnError="false" async="false" name="API-V1-InitializeAPI">
    <DisplayName>API-V1-InitializeAPI</DisplayName>
    <FaultRules/>
    <Properties/>
    <Request variable="API-V1-Request"/>
    <Response>InitializeAPIResponse</Response>
    <HTTPTargetConnection>
        <Properties/>
        <URL>https://URL?foo={bar}</URL>
    </HTTPTargetConnection>
</ServiceCallout>
3

@Sagar Mummidivarapu

Your Service Callout should be using the value of the AssignTo from of the AssignMessage not the name of the policy.

You have: .

Should be:

4

It worked like a gem. How to get the final response from service B? Now the service A issue is resolved but service B is successful but the response(supposed to be json document) is not shown. What should I do?

5

Once you get the response back from Service B, presumably in “ProductsResponse” message (note that I just faked the second service callout target):

<ServiceCallout async="false" continueOnError="false" enabled="true" name="Service-Callout-2">
    <DisplayName>Service Callout-2</DisplayName>
    <Request variable="ProductsRequest"/>
    <Timeout>300000</Timeout>
    <Response>ProductsResponse</Response>
    <HTTPTargetConnection>
        <URL>http://api.art.com/ECommerceAPI.svc/jsonp/InitializeAPI</URL>
    </HTTPTargetConnection>
</ServiceCallout>

you simply assign that to the “response” message using a final Assign Message.

<AssignMessage async="false" continueOnError="false" enabled="true" name="Assign-Message-3">
    <DisplayName>Assign Message-3</DisplayName>
    <Properties/>
    <Copy source="ProductsResponse"/>
    <Set>
        <Headers>
            <Header name="kurt-was-here">{system.time}</Header>
        </Headers>
    </Set>
    <IgnoreUnresolvedVariables>true</IgnoreUnresolvedVariables>
    <AssignTo createNew="false" transport="http" type="response"/>
</AssignMessage>

Note the AssignTo type is “response”.

6

There is only one external service call and hence one service call out should be there and its response is used for the real request api call from client. I don’t want to use two service call outs. Does it makes sense?

7

I think so, you mentioned Service A then Service B so I prototyped as a “No Target” API with 2 Service Callouts.

If your using a “Reverse Proxy” API with one or more target endpoints, then each conditional flow would need to use an Assign Message with AssignTo of type “request”.

<AssignMessage async="false" continueOnError="false" enabled="true" name="Assign-Message-products">
    <DisplayName>Assign Message-products</DisplayName>
    <AssignVariable>
        <Name>this.CustomerZoneID</Name>
        <Ref>intializeresponse.CustomerZoneID</Ref>
        <Value>ZZ</Value>
    </AssignVariable>
    <AssignVariable>
        <Name>this.CurrencyCode</Name>
        <Ref>intializeresponse.CurrencyCode</Ref>
        <Value>CC</Value>
    </AssignVariable>
    <Set>
        <QueryParams>
            <QueryParam name="customerZoneId">{this.CustomerZoneID}</QueryParam>
            <QueryParam name="currencyCode">{this.CurrencyCode}</QueryParam>
        </QueryParams>
        <Verb>GET</Verb>
    </Set>
    <IgnoreUnresolvedVariables>true</IgnoreUnresolvedVariables>
    <AssignTo createNew="false" transport="http" type="request"/>
</AssignMessage>

That also assumes your proxy endpoint (e.g. products) is also available as a backend endpoint for the TargetURL.

In any case, the secret is connecting the Service Callout request and response messages with the Extract Variables and Assign Message policies.