In this Learn Edge example, we'll use the Service Callout policy to call an external service, get back a response, and process the response by extracting data from it and setting custom headers.

Be sure to perform the prerequisites if you haven't already.

We assume you've provisioned the Product, Developer App, and Developer as explained in apikey-security. If you want to redo it, here's how:

1. cd api-platform-samples/learn-edge/provisioning.
2. ./cleanup.sh.
3. ./setup.sh.

1. cd api-platform-samples/learn-edge/service-callout-1.
2. ./deploy.sh

1. ./invoke.sh
2. Note that two custom headers are returned "x-firstName" and "x-lastName".

Go to the Edge UI and run a Trace on this API.

This proxy is a refactor of the extract-json-payload proxy. In extract-json-payload, we called the mocktarget service, got back a response, extracted data from the response, and set custom headers.

In this example, we remove the TargetEndpoint from the proxy and call the target directly using a Service Callout policy:

    <ServiceCallout name='ServiceCalloutGetMockResponse'>
        <DisplayName>ServiceCallout.GetMockResponse</DisplayName>
        <Request variable="myrequest">
        </Request>
        <Response>mockresponse</Response>
        <Timeout>30000</Timeout>
        <HTTPTargetConnection>
          <URL>http://mocktarget.apigee.net</URL>
        </HTTPTargetConnection>
    </ServiceCallout>

Notice that the policy has a target URL, much like the target you'd specify in a Target Endpoint!

Two other important things to notice about this policy:

• It takes a Request variable. As we'll see next, we use an Assign Message policy to create it.
• It sets a Response variable. This is the variable that we'll process further down the line when we extract response data and set headers.

Immediately before the Service Callout policy executes, we use Assign Message to save a custom request object. Our requirement is simple -- just set the proxy path suffix using the <Set>/<Path> element. The suffix will be added to the target URL set in the Service Callout policy.

Important: Note the use of <AssignVariable> to set target.copy.pathsuffix to false. This is required! If you don't set it to false, then the pathsuffix from the target URL will be copied instead.

    <AssignMessage name="AM-BuildRequest">
        <AssignTo createNew="true" type="request">myrequest</AssignTo>
        <IgnoreUnresolvedVariables>false</IgnoreUnresolvedVariables>
        <Set>
            <Path>/json</Path>
        </Set>
        <AssignVariable>
            <Name>target.copy.pathsuffix</Name>
            <Value>false</Value> 
        </AssignVariable>
    </AssignMessage>

• In the apiproxy/proxies/default.xml file, we attach the Assign Message and Service callout policies to the Proxy Endpoint Preflow as follows:

      ...
        <PreFlow>
          <Request>
            <Step>
              <Name>VerifyAPIKey</Name>
            </Step>
            <Step>
              <Name>AM-BuildRequest</Name>
            </Step>
            <Step>
              <Name>ServiceCalloutGetMockResponse</Name>
            </Step>
          </Request>
      ...

• Configure the proxy to call the mocktarget service with the /user path and ?user query parameter. Hint: Configure the Assign Message policy to create the appropriate request.

Copyright © 2016 Apigee Corporation

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.