Table of Contents
Reference notes
We are going to use release/release-1.0.0 as the branch for this Unit. See the link here.
POM Dependencies
Let’s explain the purpose of the dependencies in pom file:
spring-boot-starter-web
This dependency will be used to manage HTTP requests. as it contains an embedded server, it will be easy to set the server up locally.
On the other hand, we will be able to use annotations like @RestController, @GetMapping, @PutMapping, @PostMapping, @DeleteMapping, @RequestParam, and @RequestBody.
spring-boot-starter-test
This dependency will be required for unit and integration testing on our app.
spring-boot-starter-data-mongodb
For working with MongoDB, we are going to need to add this dependency to be able to make different requests to the database, and so on.
Lombok
This dependency is to simplify and reduce the amount of code. We can use getters, setters, constructors, object builders, etc.
More info here: https://projectlombok.org/
DTO (Data Transfer Object)
DTOs are simple objects used to transport data between different application layers without exposing the database entities’ internal structure.
What are DTOs for?
- Security and data control: In this way, we are going to avoid exposing ID fields, and other kinds of private or confidential content.
- Optimization on data transfers: When we have different objects that are received to the service/returned from the service and others that are created to manipulate databases, we are going to expose only the fields that have been validated previously.
- Flexibility: Changes on the database don’t have to be always reflected in the DTO class.
- Data validation: Using DTOs will make it easier to validate inputs on our service.
Entity
An entity is a Java class that has been created to manipulate specific database tables, columns, relations, or collections. They represent persistent data in the database.
Controller
To manage HTTP requests, we will need to implement a Controller. This file will be responsible for defining the DTOs (Data Transfer Objects) that will be received and returned on each endpoint.
On lower versions of Spring Boot 3.4, dependency injection was required using the @Autowired annotation. We are going to see how it works from the version we are using, in our case, V3.4.
From version V3.4 dependency injection through Constructor is highly recommended.
Service
This layer is where all business logic is going to be, it is responsible for managing the data input that comes from the Controller layer, doing all the business logic required for a specific endpoint, and then finishing the workflow returning data to the Controller. If we need to call another API, make some queries to DB, or get data from elsewhere, all business logic will happen on this layer.
Repository
These classes are where all the requests to a DB, API services, and so on happens. In our example we are going to implement MongoRepository class.