Hands-On Microservices with Kotlin

Autowiring

Part of our application may use other parts, for example, a component uses another. If we look at our example, we can see that we created a service named ExampleService and that our Controller uses it as part of the constructor. When the component scan finds our controller, because is annotated with @Controller, it will discover that our class has a constructor that receives parameters.

The constructor parameter is a class that is already in the Spring context since it is as annotated with @Service, so the component scan will get the bean on the context and sends it as a parameter to the constructor of our controller. But sometimes, we may just have this as a parameter within our class, not as a parameter in the constructor, so ...