- Dependency Injection (DI) is a software design pattern.
- According to DI all the components should be as independent as possible with other Java classes
- This increases the possibility of reusing the class and testing them independently
- In the above example if class A needs Object of class B and class C, Class A has to create objects of class B and class C. But in IOC using DI, the object of B and C is created by the Spring container for class A
- So in nutshell rather than A configuring itself by creating object for class B and C, class B and class C object are configured by the container
Advantages :
- IOC makes it loosely coupled
- We provided the Information to spring container by XML or by annotations
- There are two ways of injecting dependency
- Constructor Injection
- Dependency Injection
- Autowiring feature of the spring framework enables you to inject object dependency implicitly. It internally uses setter or constructor injection.