Project is divided into 3 main parts:

• domain - contains business domain objects and business logic and ports as interfaces
• adapter - contains adapter layer with ports implementations so called adapters
• application - which is a Spring Boot application, configuration, logic needed for Spring boot working etc

It also contains some technical folders such:

• e2e-tests-rest-client contains usefull rest client (IntelliJ) with some e2e tests
• buildSrc which is a technical folder with gradle common configuration

Contains business objects and logic (not many use cases are now implemented, see BookValidator.java).

Domain logic and data is exposed outside by the primary ports called api. This kind of ports are used for to serve business cases as a REST API, SOAP, notification pushes to 3rd parties, etc.

For internal (business purposes) it uses secendary ports called spi to reach the external information needed for the business (like goodreads.com integration for fetching pics) or internal interactions and side effects (like DB or Elasticsearch etc).

Should not contain any dependencies (only libs allowed for dev convenience like lombok, commons etc).

Implementation of ports from the domain. It contains both, internal and external, communication like DB communication, goodreads (outside world), ES, and REST api endpoints (Spring rest controllers).

It also contains mappers from domain to dto (adapter and case specific) objects.

Application needs a DB to run:

docker compose up

The database (Postgres) is filed up with a data with automatic schema creation, each time the context is started. So after app restart the data will be lost.

There should be a migration mechanism like flyway or liquibase but I had no time to configure it.

Start the app as a normal Spring boot application with some endpoints available

GET http://localhost:8080/actuator/health

POST http://localhost:8080/api/book
GET http://localhost:8080/api/book/list

e2e-tests-rest-client folder contains a simple client.rest which can be run on the IntelliJ IDEA.

Just tweak the POST payload and push "play" button. It also works as a simple test with assertions.

You can of course use other rest clients like Postman etc.