Pfps Shopping Cart Save

:shopping_cart: The Shopping Cart application developed in the book "Practical FP in Scala: A hands-on approach"

Project README


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⚠️ IMPORTANT NOTICE If you are reading the first edition of Practical FP in Scala, go to the master branch. You're now on the second-edition branch, which is the new default. ⚠️

Components Overview

Here's an overview of the different components that make this application.


  • Both Services and Authentication are algebras. The latter are mainly dependencies for some of the services.
  • Programs shows Checkout, the business logic that combines most of the services.
  • Effects show our custom interfaces required implicitly.
  • The lines connecting services to Redis and PostgreSQL show which ones access which storage.
  • The HTTP layer shows the client and the different routes.
  • At the very end, we have both the modules and the entry point to the application.

Authentication Data

For didactic purposes, this is made available but in a real application THIS SHOULD NEVER BE MADE PUBLIC.

For Admin users, the following environment variables are needed:


For access token (manipulation of the shopping cart):


For password encryption:


See the files docker-compose.yml or .env for more details.

Generate your own auth data

In order to generate a valid JWT token, you need a secret key, which can be any String, and a JWT Claim, which can be any valid JSON. You can then generate a token, as shown below:

val claim = JwtClaim(
    {"uuid": "6290c116-4153-11ea-b77f-2e728ce88125"}

val secretKey = JwtSecretKey("any-secret")

val algo = JwtAlgorithm.HS256

val mkToken: IO[JwtToken] =
  jwtEncode[IO](claim, secretKey, algo)

In our case, our claim contains a UUID, which is used to identify the Admin Id. In practice, though, a JWT can be any valid JSON.

Take a look at the TokenGenerator program to learn more.


To run Unit Tests:

sbt test

To run Integration Tests we need to run both PostgreSQL and Redis:

docker-compose up
sbt it:test
docker-compose down

Access Redis & Postgres

We can interact with both servers directly using the following commands:

$ docker-compose exec Redis /usr/local/bin/redis-cli
$ docker-compose exec Postgres usr/local/bin/psql -d store -U postgres

Build Docker image

sbt docker:publishLocal

Our image should now be built. We can check it by running the following command:

> docker images | grep shopping-cart
REPOSITORY                    TAG                 IMAGE ID            CREATED             SIZE
shopping-cart                 latest              646501a87362        2 seconds ago       138MB

To run our application using our Docker image, run the following command:

cd /app
docker-compose up

Payments Client

The configured test payment client is a fake API that always returns 200 with a Payment Id. Users are encouraged to make modifications, e.g. return 409 with another Payment Id (you can create one here) or any other HTTP status to see how our application handles the different cases.

This fake API can be modified at:

HTTP API Resources

If you use the Insomnia REST Client, you can import the shopping cart resources using the insomnia.json file.


Licensed under the Apache License, Version 2.0 (the "License"); you may not use this project except in compliance with the License. You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Open Source Agenda is not affiliated with "Pfps Shopping Cart" Project. README Source: gvolpe/pfps-shopping-cart

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