Dependency injection is a key feature of Spring (and Spring Boot). It reduces the coupling or in other words, makes the classes less dependent on one another. This increases the possibility to reuse them and also helps to test the app.
Spring provides three ways to inject the dependencies—Field, Constructor, and Setter injection:
- In field injection, you just declare the field and add an annotation on top of the field declaration. Although highly readable, this practice could go higher as the fields grow and also increases the dependence on a specific Spring container, thereby making testing difficult. Field injection is therefore not recommended.
- Constructor injection is about adding a constructor that initializes the ...
