Creating a Prototype API with Mock Payload Generated Inline Scripts

The prototype implementation in WSO2 API Manager gives users the ability to prototype APIs with inline scripts for testing purposes and as an early promotion. This allows subscribers to try out and test APIs without subscriptions or monetizations, allowing them to provide feedback to improve APIs. Publishers can use this to make changes to the APIs requested by users. The WSO2 API Manager prototype implementation allows you to generate a mock payload based on an API definition. You can prototype an API using the inbuilt JavaScript engine without having to manually write the JavaScript implementation for each resource.

Let's create a prototyped API with mock response payloads, deploy it as a prototype, and invoke it using the API Console, which is integrated into the Developer Portal.

For this let's use the following OpenAPI URL:

Step 1 - Create a prototype API with mock response payloads

  1. Click CREATE NEW API, and click I Have an Existing REST API.

    Create API options

  2. Upload the OpenAPI URL or OpenAPI File and click NEXT.

    Filled create api form for existing

  3. Provide the API name, context, and version. Thereafter, click CREATE.

    Filled create api form

    Now you will be directed to the API overview page.

  4. Click Endpoints to navigate to the Endpoints page.

  5. Select Prototype Implementation as the endpoint type, and click Proceed.

    Selecting Prototype Implementation to add

    The Endpoints page appears.

    List of endpoints in Inline script page

  6. Click and expand any of the methods that contain a sample/mock payload to view the inline script that has been generated.

    Generated inline script

    The example response defined in the OpenAPI definition is set as the mock response payload. You can modify the generated inline scripts as required.

  7. Modify the inline script for /pet/{petId}.

    Set a path parameter entered by the user to a variable that will satisfy a condition and set a response accordingly.


    The RESET button appears after a change is made to the script. When pressed, the script will revert back to the originally generated script.

    Modified inline script

    // **GENERATED CODE** //
    var responses = [];
    if (!responses[200]) {
     responses [200] = [];
    responses[200]["application/json"] = {                 // Mock response payload stored as a variable
      "id" : 10,
      "name" : "doggie",
      "category" : {
        "id" : 1,
        "name" : "Dogs"
      "photoUrls" : [ "string" ],
      "tags" : [ {
        "id" : 0,
        "name" : "string"
      } ],
      "status" : "available"
    if (mc.getProperty('uri.var.petId') == 1) {          // Get the path parameter 'petID' to check the condition
      responses[200]["application/json"] = {
        "id" : 1,
        "category" : {
          "id" : 1,
          "name" : "Dog"
        "name" : "doggie",
        "photoUrls" : [ "" ],
        "tags" : [ {
          "id" : 1,
          "name" : "German Sheperd"
        } ],
        "status" : "available"
      responses[200]["application/xml"] = <pet><id>1</id><name>doggie</name><category><id>1</id><name>Dog</name></category><photoUrls><photoUrl>;ixlib=rb-1.2.1&amp;auto=format&amp;fit=crop&amp;w=1396&amp;q=80</photoUrl></photoUrls><tags><tag><id>1</id><name>German Sheperd</name></tag></tags><status>available</status></pet>;
    // **GENERATED CODE** //
    if (accept == "application/json") {
     mc.setProperty('CONTENT_TYPE', 'application/json');
    } else if (accept == "application/xml") {
     mc.setProperty('CONTENT_TYPE', 'application/xml');

    Inline Script Methods

    The following table lists down the mc. methods that you can use to invoke functions in the inline script. You can use these functions to access the Synapse predefined in a script variable named mc. The mc variable represents an implementation of the MessageContext, named, which contains the following methods, that you can access within the script as mc.methodName.

    Return? Method Name Description
    Yes getPayloadXML() This gets an XML representation of SOAP body payload.
    No setPayloadXML(payload) This sets the SOAP body payload from XML.
    Yes getEnvelopeXML() This gets the XML representation of the complete SOAP envelope.
    No setTo(reference) This is used to set the value that specifies the receiver of the message.
    Yes setFaultTo(reference) This is used to set the value that specifies the receiver of the faults relating to the message.
    No setFrom(reference) This is used to set the value that specifies the sender of the message.
    No setReplyTo(reference) This is used to set the value that specifies the receiver of the replies to the message.
    Yes getPayloadJSON() This gets the JSON representation of a SOAP Body payload.
    No setPayloadJSON( payload ) This sets the JSON representation of a payload obtained via the getPayloadJSON() method and sets it in the current message context.
    Yes getProperty(name) This gets a property from the current message context.
    No setProperty(key, value) This is used to set a property in the current message context. The previously set property values are replaced by this method.
  8. Click SAVE to save the API.

    Save button Inline scripts page

Step 2 - Deploy the API as a prototype

  1. Click Lifecycle to navigate to the Lifecycle page.

  2. Click DEPLOY AS A PROTOTYPE to deploy the API as a prototype.

    Lifecycle page

Step 3 - Invoke the API

  1. Click View in Dev Portal to navigate to the Developer Portal after the API is deployed.

  2. Click Try Out to navigate to the API Console.

    Devportal overview

  3. Expand any method and click Try it out.

    Tryout click

  4. Enter the value for the parameter and click Execute to invoke the API.


    The payload that you gave as a JSON/XML output appears in the response for each respective parameter provided.

    1. For petId : " 0 "

      Tryout for petid0

      Sample cURL command to invoke the API

      curl -X GET "https://localhost:8243/v3/1.0.5/pet/0" -H "accept: application/json"

      The response payload that is defined in the generated script is returned.

      Response for petid0

    2. For petId : " 1 "

      Tryout for petid1

      Sample cURL command to invoke the API

      curl -X GET "https://localhost:8243/v3/1.0.5/pet/1" -H "accept: application/json"

      The response payload defined in the manually modified script is returned.

      Response for petid1

You have successfully created an API with an inline script, deployed it as a prototype, and invoked it via the integrated API Console.

An API can also be prototyped by moving the API to the PROTOTYPED state by changing the API lifecycle state and providing the prototype endpoints.

For more information, see the Deploy and Test Prototype APIs tutorial.