Scala Rest API with akka-http

2-minute read
Technical
akka • akka-http • rest service • sbt • scala • scala example • web service

Introduction

In this tutorial we shall explore how we can use akka-http to create service with scala. Here we create CRUD service with akka actor and try to see how it work.

Versions

  • Scala version: 2.13.1
  • SBT version: 1.3.4

Other dependencies

About the service/project

We’ll create two actors that communicate with each other to get the user data and user activity data.

output of the application

Data Classes

We need two data classes that keeps the user data and user activity data.

Repository

Repositories are used to fetch the data from the actual source of data. The actual source can be anything like another service or some database. We created UserActivityRepository that have only one method queryHistoricalActivities to fetch the user activity by userId.

Actors to get user data

We need two actor classes for UserDataActor and UserActivityActor. UserDataActor received 4 types of methods Get, Post,Put and Delete to retrieve, create, update and delete the user data respectively. Once a message received, User data will be sent to the sender asynchronously.

UserActivityActor retrieve the user active once it receives the message Get

Routing Configuration

Now, we need to create routing details, to access the user details from rest endpoints. We needs following endpoints

Path Detail
GET /api/users/activity Retrieve user and its activity details.
POST /api/user To create user data
PUT /api/user To update user data
DELETE /api/user To delete user data

Routing code looks like below -

We have two implicit parameters in the routing config implicit val userDataActorRef: ActorRef and implicit val system: ActorSystem. userDataActorRef is used to get the user data. Since user details is required to register UserActivityActor we use actor system and implicit parameter to register UserActivityActor when we have user information available.

Web Server

This class is used to create http server and bind the endpoints with the http server.

Run Application

Compile the code using below command 

sbt compile

Run the application

sbt run

Now go to terminal, and run below httpie scripts output of the application

Github links

Full code is available here to explore and fork. Feel free to do whatever you want. ;)

Conclusion

We have seen here it’s easy to create rest services with akka and scala. You can get more information at akka-http official document.