What is Dependency Injection and Inversion of Control in Spring Framework?

Question

\"Dependency Injection\" and \"Inversion of Control\" are often mentioned as the primary advantages of using the Spring framework for developing Web frameworks

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Answer 1

In Spring Objects are loosely coupled i.e., each class is independent of each other so that everything can be tested individually. But when using those classes, a class may be dependent on other classes which need to be instantiated first.

So, we tell spring that class A is dependent on class B. So, when creating bean(like class) for class A, it instantiates class B prior to that of class A and injects that in class A using setter or constructor DI methods. I.e., we are telling spring the dependency at run-time. This is DI.

As, we are assigning the responsibility of creating objects(beans), maintaining them and their aggregations to Spring instead of hard-coding it, we call it Inversion Of Control(IOC).