How to Connect Mendix to a REST API

Mendix is a low-code development platform that enables users to build scalable, enterprise-grade applications rapidly. One of the most powerful features of Mendix is its ability to integrate seamlessly with external systems via REST APIs. Whether you're fetching data from a third-party service, sending updates to a backend, or integrating with an enterprise system, Mendix provides a straightforward way to consume and expose REST APIs.

In this blog, we’ll walk through the step-by-step process of connecting Mendix to a REST API as a consumer, using built-in tools and best practices.


🔧 Why Use REST APIs in Mendix?

REST APIs allow Mendix apps to:

Integrate with external systems (e.g., weather, payment gateways, ERP)

Extend app functionality without duplicating business logic

Exchange data in real time

Enhance the user experience with live, external data


🪜 Step-by-Step: Connecting Mendix to a REST API

Step 1: Understand the API Requirements

Before integrating any API, gather key information:

Base URL (e.g., https://api.example.com)

Endpoints (e.g., /users, /products)

Authentication method (e.g., API key, OAuth)

Data format (usually JSON)

Request/Response structure


Step 2: Create the Data Model

In Mendix Studio Pro:

Create entities that match the structure of the API response.

Use non-persistent entities for temporary data (e.g., listing weather info).

Example:

plaintext


Entity: Weather

- temperature (Decimal)

- description (String)

- location (String)


Step 3: Configure the REST Call

Mendix provides the Call REST service activity in microflows.

Create a microflow to handle the API call.

Drag and drop the Call REST service activity.

Set the HTTP method (GET, POST, etc.).

Enter the URL (can be static or dynamic).

Set up headers (e.g., API key or content type).

Map the response to your entity (via import mapping).


Step 4: Create Import Mapping

Use Import Mapping to convert JSON responses into Mendix objects.

Go to Import Mapping under the Navigation bar.

Choose Create from JSON structure.

Paste a sample API response.

Map fields to your non-persistent entity (e.g., Weather).

Save and link the mapping in the REST call activity.


Step 5: Display the Data in UI

After retrieving the data:

Pass the result from your microflow to a data view.

Bind the non-persistent entity to a page widget.

Use text widgets, images, and lists to show the data in your app.


Step 6: Add Error Handling and Logging

Use error handlers in the microflow to catch HTTP errors.

Log the error using the Log message action.

Provide a user-friendly message (e.g., “Unable to fetch data. Please try again.”).


🧠 Best Practices

Use constants for API URLs and keys.

Secure API keys using environment variables or app settings.

Use sub-microflows to reuse REST logic.

Cache responses if the API is rate-limited or slow.


✅ Conclusion

Connecting Mendix to a REST API is simple yet powerful. By using the platform’s built-in tools like microflows, import mappings, and non-persistent entities, developers can quickly build apps that interact with external services. Whether you’re pulling product data from a CMS or posting orders to an ERP, Mendix provides a flexible and secure way to handle REST integrations with minimal code and maximum efficiency. 

Learn Mendix Training

Read More : Using Mendix Widgets for Enhanced UI
Read More : Mendix Domain Model: How to Structure Your Data
Read More : Setting Up Your Mendix Development Environment


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