How to Call Third Party REST API Integrations in ServiceNow Using GlideAjax & Script Includes

[BillMartin]

Integrating REST APIs in ServiceNow can be challenging, especially when dealing with multiple external systems. Without a structured approach, things can quickly become messy, making it difficult to debug and maintain.

Let’s walk through a scalable and efficient way to integrate external APIs using GlideAjax, Script Includes, and RESTMessageV2. This method ensures smooth client-server communication, reusable code, and a consistent data structure.

Why This Matters for ServiceNow Developers

If you've ever struggled with inconsistent API responses, repetitive Ajax calls, or debugging errors with REST integrations, this approach will help you simplify everything. We’ll break it down into key components:

• GlideAjax for making client-to-server requests asynchronously
• BaseAjaxProcessor to handle multiple API calls in a reusable way
• RESTMessageV2 for making secure external API requests
• EmployeeEntity to standardize responses across different layers

Instead of writing separate logic for every API call, this approach centralizes everything, improving efficiency and performance.

How This Works in ServiceNow

A client script (such as a button click or form event) triggers a request using GlideAjax. This request is sent to a Script Include (EmployeeAjax), which then calls BaseAjaxProcessor. From there, EmployeeService handles business logic and reaches out to EmployeeRepository, which makes an actual REST API request using RESTMessageV2. Once the response is received, it’s structured into a standardized format using EmployeeEntity, ensuring every response is clean and usable before being sent back to the client.

This method keeps everything modular. Need to call a different API? Just update the repository. Need to change the response format? Modify the entity model without affecting the entire system.

Why This Approach Works Best

ServiceNow’s GlideAjax allows the UI to remain responsive while API requests run in the background. BaseAjaxProcessor keeps things clean by reusing logic for multiple API calls. EmployeeEntity ensures that API responses are always formatted properly, preventing data inconsistencies. With structured logging through BaseLogger, debugging API failures becomes much easier.

Where This Can Be Used

This method is perfect for pulling employee data from an HR system, syncing incidents across ITSM platforms, handling financial transactions from an external payment processor, or tracking assets through an external CMDB.

Watch It in Action

We’ve covered the best practices, but seeing it in action will really help you understand how it works. Watch our live demo where we break down the implementation, step by step, and show you how to apply this method in your own ServiceNow environment.

Have you struggled with REST API integrations in ServiceNow? Share your experience in the comments—we’d love to hear how you’re solving these challenges!

[bilomen]

great