rest-client

REST Integration Skill

Use this skill when integrating with external REST APIs from Mendix.

Three Approaches

Mendix offers three ways to call REST APIs from microflows. Choose based on the use case:

Approach	When to Use	Artifacts
OpenAPI import	API has an OpenAPI 3.0 spec — auto-generate from the spec	REST client document generated in one command
REST Client (manual)	No spec available, or need fine-grained control	REST client document + microflow
REST CALL (inline)	One-off calls, quick prototyping, dynamic URLs, low-level HTTP control	Microflow only

Both REST Client approaches can be combined with Data Transformers (Mendix 11.9+) and Import/Export Mappings to map between JSON and entities.

No API to call against yet — or one you would rather not depend on while building? mock-rest-apis covers standing up an endpoint you control and pointing the app at it.

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Approach 0: OpenAPI Import (Fastest)

If the API has an OpenAPI 3.0 spec (JSON or YAML), generate the REST client in one command:

-- From a local file (relative to the .mpr file)
create or modify rest client CapitalModule.CapitalAPI (
  OpenAPI: 'specs/capital.json'
);

-- From a URL
create or modify rest client PetStoreModule.PetStoreAPI (
  OpenAPI: 'https://petstore3.swagger.io/api/v3/openapi.json'
);

-- Override the base URL (replaces servers[0].url from the spec)
create or modify rest client PetStoreModule.PetStoreStaging (
  OpenAPI: 'https://petstore3.swagger.io/api/v3/openapi.json',
  BaseUrl: 'https://staging.petstore.example.com/api/v3'
);

This generates:

• All operations with correct HTTP method, path, parameters, headers, body, and response type
• Resource groups based on OpenAPI tags
• Basic auth if the spec declares it at the top level
• The spec stored inside the document for Studio Pro parity

BaseUrl is optional. When omitted, servers[0].url from the spec is used — but only if it is absolute. A relative server URL (/api/v3) cannot be a BaseUrl: the import warns ("server URL … is relative and cannot be used as BaseUrl") and leaves the client without one, which fails at call time rather than at import time. Set BaseUrl explicitly in that case.