Building a REST API with Nitric
This guide will show you how to build a serverless REST API with the Nitric framework using Dart. The example API enables reading, writing and editing basic user profile information using a Nitric key value store to store user data. Once the API is created we'll test it locally, then optionally deploy it to a cloud of your choice.
The example API enables reading, writing, and deleting profile information from a Nitric key value store.
The API will provide the following routes:
Method | Route | Description |
---|---|---|
GET | /profiles/[id] | Get a specific profile image by its id |
GET | /profiles | List all profiles |
POST | /profiles | Create a new profile image |
DELETE | /profiles/[id] | Delete a profile |
There is also an extended section of the guide that adds file operations using a Nitric bucket to store and retrieve profile pictures using signed URLs. The extension adds these routes to the API:
Method | Route | Description |
---|---|---|
GET | /profiles/[id]/image/upload | Get a profile image upload URL |
GET | /profiles/[id]/image/download | Get a profile image download URL |
GET | /profiles/[id]/image/view | View the image that is downloaded |
Prerequisites
- Dart
- The Nitric CLI
- An AWS, Google Cloud or Azure account (your choice)
Getting started
Start by creating a base Dart
dart create -t console my-profile-api
Add the Nitric SDK and the uuid dependency by adding it to your pubspec.yaml
.
dependencies:nitric_sdk: ^1.2.0uuid: ^4.3.3
Next, open the project in your editor of choice.
cd my-profile-api
The scaffolded project should have the following structure:
bin/├── my_profile_api.dartlib/├── my_profile_api.darttest/├── my_profile_api_test.dart.gitignoreanalysis_options.yamlCHANGELOG.mdpubspec.lockpubspec.yamlREADME.md
To create our Nitric project, we have to create a nitric.yaml
file. The handlers key will point to where our
name: my_profile_apiservices:- match: bin/my_profile_api.dartstart: dart run $SERVICE_PATH
Create a Profile class
We will create a class to represent the profiles that we will store in the key value store. We will add toJson
and fromJson
functions to assist.
class Profile {String name;int age;String homeTown;Profile(this.name, this.age, this.homeTown);Profile.fromJson(Map<String, dynamic> contents): name = contents["name"] as String,age = contents["age"] as int,homeTown = contents["homeTown"] as String;Map<String, dynamic> toJson() => {'name': name,'age': age,'homeTown': homeTown,};}
Building the API
Applications built with Nitric can contain many APIs, let's start by adding one to this project to serve as the public endpoint. Rename bin/my_profile_api.dart
to bin/profiles.dart
import 'package:nitric_sdk/nitric.dart';import 'package:nitric_sdk/resources.dart';import 'package:uuid/uuid.dart';void main() {// Create an API named 'public'final profileApi = Nitric.api("public");// Define a key value store named 'profiles', then request get, set and delete permissions.final profiles = Nitric.kv("profiles").allow([KeyValuePermission.get,KeyValuePermission.set,KeyValuePermission.delete]);}
Here we're creating an API named public
and a key value store named profiles
, then requesting get, set, and delete permissions which allows our function to access the key value store.
Resources in Nitric like api
and key value store
represent high-level
cloud resources. When your app is deployed Nitric automatically converts these
requests into appropriate resources for the specific
provider. Nitric also takes care
of adding the IAM roles, policies, etc. that grant the requested access. For
example the key value stores
resource uses DynamoDB in AWS or FireStore on
Google Cloud.
Create profiles with POST
Let's start adding features that allow our API consumers to work with profile data.
You could separate some or all of these handlers into their own files if you prefer. For simplicity we'll group them together in this guide.
profileApi.post("/profiles", (ctx) async {final uuid = Uuid();final id = uuid.v4();final profile = Profile.fromJson(ctx.req.json());// Store the new profile in the profiles kv storeawait profiles.set(id, profile);// Send a success response.ctx.res.body = "Profile $id created.";return ctx;});
Retrieve a profile with GET
profileApi.get("/profiles/:id", (ctx) async {final id = ctx.req.pathParams["id"]!;try {// Retrieve and return the profile datafinal profile = await profiles.get(id);ctx.res.json(profile.toJson());} on Exception catch (e) {print(e);ctx.res.status = 404;ctx.res.body = "Profile $id not found.";}return ctx;});
Remove a profile with DELETE
profileApi.delete("/profiles/:id", (ctx) async {final id = ctx.req.pathParams["id"]!;// Delete the profiletry {await profiles.delete(id);ctx.res.body = "Profile $id removed.";} on Exception catch (e) {ctx.res.status = 404;ctx.res.body = "Profile $id not found. $e";}return ctx;});
Ok, let's run this thing!
Now that you have an API defined with handlers for each of its methods, it's time to test it locally.
nitric start
Once it starts, the application will receive requests via the API port. You can use the Local Dashboard or any HTTP client to test the API. We'll keep it running for our tests. If you want to update your functions, just save them, they'll be reloaded automatically.
Test the API
Below are some example requests you can use to test the API. You'll need to update all values in brackets []
and change the URL to your deployed URL if you're testing on the cloud.
Create Profile
curl --location --request POST 'http://localhost:4001/profiles' \--header 'Content-Type: text/plain' \--data-raw '{"name": "Peter Parker","age": "21","homeTown" : "Queens"}'
Fetch Profile
curl --location --request GET 'http://localhost:4001/profiles/[id]'
Fetch All Profiles
curl --location --request GET 'http://localhost:4001/profiles'
Delete Profile
curl --location --request DELETE 'http://localhost:4001/profiles/[id]'
Deploy to the cloud
At this point, you can deploy the application to any supported cloud provider. Start by setting up your credentials and any configuration for the cloud you prefer:
Next, we'll need to create a stack
. Stacks represent deployed instances of an application, including the target provider and other details such as the deployment region. You'll usually define separate stacks for each environment such as development, testing and production. For now, let's start by creating a dev
stack.
nitric stack new
? What should we name this stack? dev? Which provider do you want to deploy with? aws? Which region should the stack deploy to? us-east-1
AWS
Cloud deployments incur costs and while most of these resource are available with free tier pricing you should consider the costs of the deployment.
In the previous step we called our stack dev
, let's try deploying it with the up
command.
nitric up┌───────────────────────────────────────────────────────────────┐| API | Endpoint || main | https://XXXXXXXX.execute-api.us-east-1.amazonaws.com |└───────────────────────────────────────────────────────────────┘
When the deployment is complete, go to the relevant cloud console and you'll be able to see and interact with your API. If you'd like to make changes to the API you can apply those changes by rerunning the up
command. Nitric will automatically detect what's changed and just update the relevant cloud resources.
When you're done testing your application you can tear it down from the cloud, use the down
command:
nitric down
Optional - Add profile image upload/download support
If you want to go a bit deeper and create some other resources with Nitric, why not add images to your profiles API.
Access profile buckets with permissions
Define a bucket named profilesImg
with reading/writing permissions.
final profilesImg = Nitric.bucket("profilesImg").allow([BucketPermission.read, BucketPermission.write]);
Get a URL to upload a profile image
profileApi.get("/profiles/:id/image/upload", (ctx) async {final id = ctx.req.pathParams["id"];// Return a signed upload URL, which provides temporary access to upload a file.final photoUrl = await profilesImg.file("images/$id/photo.png").getUploadUrl();ctx.req.body = photoUrl;return ctx;});
Get a URL to download a profile image
profileApi.get("/profiles/:id/image/download", (ctx) async {final id = ctx.req.pathParams["id"];// Return a signed download URL, which provides temporary access to download a file.final photoUrl = await profilesImg.file("images/$id/photo.png").getDownloadUrl();ctx.req.body = photoUrl;return ctx;});
You can also return a redirect response that takes the HTTP client directly to the photo URL.
profileApi.get("/profiles/:id/image/view", (ctx) async {final id = ctx.req.pathParams["id"];// Redirect to a signed read-only file URL.final photoUrl = await profilesImg.file("images/$id/photo.png").getDownloadUrl();ctx.res.status = 303;ctx.res.headers["Location"] = [photoUrl];return ctx;});
Test the extended API
Update all values in brackets []
and change the URL to your deployed URL if you're testing on the cloud.
Get an image upload URL
curl --location --request GET 'http://localhost:4001/profiles/[id]/image/upload'
Using the upload URL with curl
curl --location --request PUT '[url]' \--header 'content-type: image/png' \--data-binary '@/home/user/Pictures/photo.png'
Get an image download URL
curl --location --request GET 'http://localhost:4001/profiles/[id]/image/download'