API Builder Blocks


This guide covers the basic instructions for creating Blocks. Blocks are functions that run before or after an API endpoint is executed. They can be used to modify the API request, to modify the API response or to execute common tasks like audit logging, caching, rate-limiting, or recording analytics. Multiple Blocks can be executed before or after an API request. Blocks are optional.

Block definition

Place all Block files in the project's blocks folder. You can only declare one Block per file. A Block file is a JavaScript file, which:

  1. Loads the @axway/api-builder-runtime module.
  2. Calls the module's Block.extend() method, passing in an object defining the block identifier and logic to execute.
  3. Exports the defined block using the module.exports variable.

Set the following keys in the object passed to the Block.extend() method to define the Block:

Name Required Description
name true Block name. This name should be used when specifying blocks in your API endpoint definition. Assign the name value to either the before or after property in the API definition object to use it.
description true Human useful description to display in the documentation.
action true The function containing the logic for your block. All of your runnable code goes in the action function. This function is passed a request and response.


The following Block sets the set parameter and logs the change.

var APIBuilder = require('@axway/api-builder-runtime');

var PreBlock = APIBuilder.Block.extend({
    name: 'pre_example',
    description: 'will set a header named "Foo"',

    action: function (req, resp) {
        // this is a synchronous block since it doesn't have a nex
        resp.set('Foo', 'Bar');
        req.log.info('Pre Example Block executed');

module.exports = PreBlock;

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