Dependency Injection in Spring Boot

 

What is Dependency Injection?

Injecting dependency to the class from outside (External service - Spring Container).

Why Dependency Injection?

We want to achieve loose coupling.

How we will do Dependency injection in Spring and Spring boot?

Spring: we will create an external XML file (let's say bean.xml) and from XML we will inject dependencies.

Spring Boot: write the annotation @Component above the dependent class by writing @component above any class we are making that class component of spring framework, the class which wants the object of the dependent class has to mention @Autowired above the object reference.

Ex.

@Components

class HitachiHD implements HardDrive{............}

class Laptop{

@Autowired

HardDrive obj;

}

ScreenShot

Car Interface

Alto car as Spring Component

Autowire with Spring IoC

Benefits of Dependency injection:

1. Loose coupling

2. Easy unit testing