--- schema_version: "1" id: 833b8f9b787f49cbbb7657d18d4e797c6e0a0ae5385dae98f9bfa77eed8e6952 title: Building, Implementing, and Testing a REST API collection: mulesoft version: current locale: en-us portal_url: https://docs.salesforce.com/mulesoft/current/en-us/apikit/latest/apikit-4-implement-rest-api.md canonical_url: https://docs.mulesoft.com/apikit/latest/apikit-4-implement-rest-api source_site: docs.mulesoft.com content_type: documentation content_hash: f069d115c9aea3547acac7b1535ce3cb2a3bf504ff6bab9f696c0ef6ca558128 description: MuleSoft Documentation Site release: 4.x latest: true --- --- product: APIkit version: 4.x is-latest-version: true --- # Building, Implementing, and Testing a REST API > For the full documentation index, see: https://docs.mulesoft.com/llms.txt Follow this end-to-end workflow to design, implement, and test a REST API in Anypoint Studio. The example relies on the public [{JSON} Placeholder](https://jsonplaceholder.typicode.com) service, which returns mocked user JSON so you can build and validate flows without hosting a backend. ## Before You Begin Ensure you have the following software installed: - Anypoint Studio 7.1.4 or later - Mule runtime engine 4.1.1 or later ## Design Your API Specification Design your API specification with API Designer from Design Center, with the API Specification Project tool from Anypoint Studio, or with a text editor of your choice: > [!NOTE] Anypoint Studio does not support OAS 3.1. Design OAS 3.1 specifications in > [Anypoint Code Builder](https://docs.mulesoft.com/anypoint-code-builder/). 1. Create a JSON file including a list of users that serve as an example of what the service returns: \[ { "id": 1, "name": "Leanne Graham", "username": "Bret", "email": "Sincere@april.biz", "address": { "street": "Kulas Light", "suite": "Apt. 556", "city": "Gwenborough", "zipcode": "92998-3874", "geo": { "lat": "-37.3159", "lng": "81.1496" } }, "phone": "1-770-736-8031 x56442", "website": "hildegard.org", "company": { "name": "Romaguera-Crona", "catchPhrase": "Multi-layered client-server neural-net", "bs": "harness real-time e-markets" } } \] 2. Save it as `user-example.json`. 3. Create a new blank file with the following API specification: ```yaml #%RAML 1.0 title: placeholder version: 1.0 /users: get: description: Retrieve a list of all the users responses: 200: body: application/json: example: !include user-example.json /userbyid: get: description: Get information about a particular user queryParameters: id: description: Specify the id of the user you want to retrieve type: integer required: false example: 3 responses: 200: body: application/json: example: | [ { "id": 3, "name": "Clementine Bauch", "username": "Samantha", "email": "Nathan@yesenia.net", "address": { "street": "Douglas Extension", "suite": "Suite 847", "city": "McKenziehaven", "zipcode": "59590-4157", "geo": { "lat": "-68.6102", "lng": "-47.0653" }, }, "phone": "1-463-123-4447", "website": "ramiro.info", "company": { "name": "Romaguera-Jacobson", "catchPhrase": "Face to face bifurcated interface", "bs": "e-enable strategic applications", } } ] ``` 4. Save it as `api.raml`. 5. In Studio, select **File** > **New** > **Mule Project**. 6. In **Project Name**, type the name of your Mule project. - If you are importing your API specification from Exchange, select **Import a published API**, click the plus icon, and select **From Exchange**. ![\*Import a published API\* highlighted when clicking on plus to select the From Exchange option](/mulesoft/current/en-us/apikit/latest/_images/import-from-exchange.png) - If you are importing your API specification from a local file in your file system, select **Import RAML from Local File**. ![\*Import RAML from local file\* highlighted in the API implementation section](/mulesoft/current/en-us/apikit/latest/_images/import-from-local-file.png) - If you are importing your API specification from Design Center, select **Download RAML from Design Center**. ![\*Import from Design Center\* highlighted in the API implementation section](/mulesoft/current/en-us/apikit/latest/_images/import-from-design-center.png) 7. Select **Scaffold flows from these API specifications** if not already selected. 8. Click **Finish**. APIkit generates the necessary flows based on the API specification you imported. 9. Run your APIkit project by clicking **Run** > **Run As** > **Mule Application**. ## Simulate API Calls 1. In Anypoint Studio, locate the **APIkit Consoles** view and click **Open console** under the base point URL `http://localhost:8081/console/`. ![APIkit console tab displays the location of the basepoint URL in the window.](/mulesoft/current/en-us/apikit/latest/_images/apikit-consoles.png) 2. Your default browser opens. The **API Console** shows the API summary and information about the project, such as the title, version, and supported protocols. ![API console version info](/mulesoft/current/en-us/apikit/latest/_images/apikit-console1.png) 3. In **API Summary**, select `GET` for the `/users` resource. It opens a detail page of the resource showing, among others, the expected JSON example for an HTTP 200 response. ![APIkit response](/mulesoft/current/en-us/apikit/latest/_images/apikit-console3.png) 4. In **API Summary**, expand `/userbyid`. 5. Select `GET` for the `/usersbyid` resource. 6. Click `Try it` to expand the view for sending a request. The **API Console** displays a section to add parameters and headers to try a request. 7. Select **Show optional parameters** if not selected. 8. Type `3` as a query parameter value for the `id` parameter and click `Send`. An HTTP 200 response confirms the successful request for the `/usersbyid` resource, which contains user information for the user with ID 3. This response also includes the body with a JSON example. ![Information for the user having id 3 highlighted](/mulesoft/current/en-us/apikit/latest/_images/apikit-console4.png) ## Add Business Logic to Your API Implementation Modify the flows to return actual data from the JSON Placeholder service instead of the examples from the API. 1. Drag a new **Flow** component from the **Mule Palette**. 2. Rename the new flow as `user_request_flow`. 3. Drag an **HTTP Request** component to the flow process. 4. In the properties editor of **Request**, in **General**, set the following HTTP request options: - In **Method**, leave the default `GET`. - In **Path**, set to `/users`. - On **Query Parameters**, select **Switch to expression mode** and paste the following DataWeave script: output application/java --- if (not isEmpty(attributes.queryParams)) { id : attributes.queryParams.id } else {} 5. Delete **Transform Message** component in `get:\users:api-config` and `get:\users\userbyid:api-config` flows. 6. Drag one **Flow Reference** for each flow in replacement of the removed **Transform Message** components. 7. In the properties editor of **Flow Reference** components, set flow name as `user_request_flow`. 8. Save changes. ## Test Your API Implementation 1. In Package Explorer, right-click the project name and choose **Run As** > **Mule Application**. 2. Open a browser and go to `http://localhost:8081/api/users`. The user information from the JSON Placeholder service is returned: \[ { "id": 1, "name": "Leanne Graham", "username": "Bret", "email": "Sincere@april.biz", "address": { "street": "Kulas Light", "suite": "Apt. 556", "city": "Gwenborough", "zipcode": "92998-3874", "geo": { "lat": "-37.3159", "lng": "81.1496" ... { "id": 10, "name": "Clementina DuBuque", "username": "Moriah.Stanton", "email": "Rey.Padberg@karina.biz", "address": { "street": "Kattie Turnpike", "suite": "Suite 198", "city": "Lebsackbury", "zipcode": "31428-2261", "geo": { "lat": "-38.2386", "lng": "57.2232" } ... \] 3. Get information about the user having ID = 4 by going to `http://localhost:8081/api/users/userbyid?id=4`. \[ { "id": 4, "name": "Patricia Lebsack", "username": "Karianne", "email": "Julianne.OConner@kory.org", "address": { "street": "Hoeger Mall", "suite": "Apt. 692", "city": "South Elvis", "zipcode": "53919-4257", "geo": { "lat": "29.4572", "lng": "-164.2990" } }, "phone": "493-170-9623 x156", "website": "kale.biz", "company": { "name": "Robel-Corkery", "catchPhrase": "Multi-tiered zero tolerance productivity", "bs": "transition cutting-edge web services" } } \] Your REST API creation, implementation, and testing are complete. ## See Also - [{JSON} Placeholder](http://jsonplaceholder.typicode.com) - [Tutorial: Build an API from Start to Finish](https://docs.mulesoft.com/general/api-led-overview) - [Create and Publish an API Specification or API Fragment with Design Center](https://docs.mulesoft.com/design-center/design-create-publish-api-specs)