How to Consume REST APIs in OutSystems Step by Step

In Service Studio, click the Logic tab on the right-hand panel. Expand Integrations. Right-click REST and select Consume REST API. A dialog appears with two options: Add Single Method (for one endpoint at a time) or Add Multiple Methods (for OpenAPI/Swagger specs). For a quick start, choose Add Single Method.

In the Method URL field, enter the full endpoint URL. Use curly braces for path parameters — for example: GET https://jsonplaceholder.typicode.com/posts/{id}. Service Studio automatically creates an input parameter called Id (Integer) based on the {id} placeholder. Set the HTTP Method dropdown to GET, POST, PUT, or DELETE as appropriate. In the Headers/Auth tab, add any required headers such as Authorization or X-API-Key.

Click the Test tab inside the dialog. Fill in any required input parameters (e.g., enter 1 for {id}). Click the Test button. Service Studio makes a live HTTP call and displays the raw JSON response. Click Copy to Response Body — this populates the Response tab with the actual JSON payload. Service Studio uses this sample to generate the output structure with correct field names and data types.

Click the Response tab to review the mapping. Service Studio converts JSON types to OutSystems types: string → Text, number → Integer or Decimal, boolean → Boolean, object → Structure, array → List. Rename any generated structures or attributes if needed by clicking directly on them. Verify the output structure matches the shape of data you expect to use in your app. When satisfied, click OK to complete the import. Service Studio creates: the REST API node under Logic tab → Integrations → REST, a method action (e.g., GetPost), input/output parameters, and any Structures under Data tab → Structures.

Go to Logic tab → Server Actions → right-click → Add Server Action. Name it, for example, FetchPost. Add an input parameter PostId (Integer) and output parameter PostData (the generated output structure type). Inside the action flow, drag the generated method action (GetPost) from the toolbox or from Integrations → REST → [YourAPI] into the flow between Start and End. Set the method's Id input to PostId. Add an Assign node after the method call. In the Assign, set PostData = GetPost.Response. Action flow: Start → GetPost (Id = PostId) → Assign (PostData = GetPost.Response) → End

Open (or create) a Reactive Web screen. Right-click the screen name → Fetch data from Other Sources — this creates a Data Action. Inside the Data Action, drag your FetchPost Server Action into the flow. Pass an appropriate PostId value (e.g., a screen input parameter or a hardcoded value like 1). Add an Output Parameter to the Data Action that holds the returned structure. Back on the screen canvas, drag Expression widgets from the toolbox and set their Value to reference fields from the Data Action output — for example: DataAction1.PostData.Title. 1-Click Publish (Ctrl+F5) to deploy.

REST calls can fail (network issues, server errors, bad credentials). In your FetchPost Server Action, right-click the flow after the GetPost method call → Add Exception Handler → select Communication Exception. Inside the handler, add a Raise Exception node or an Assign that sets an error output parameter. Alternatively, wrap the API call in a try-style pattern: add an Exception Handler for AllExceptions at the Server Action level and log the error using the LogError system action from the (System) module. Action flow with error handling: Start → GetPost → [Exception Handler: Communication Exception] → Assign ErrorMessage → End