3. Setter Based Bean Injection  

Constructor Based Bean Injection 

Dependency injection is a pattern we can use to implement IoC, where the control is inverted in setting an object’s dependencies.

Connecting objects with other objects, or “injecting” objects into other objects, is done by an assembler rather than by the objects themselves.

In the case of constructor-based dependency injection, the container will invoke a constructor with arguments each representing a dependency we want to set. Spring resolves each argument primarily by type, followed by name of the attribute, and index for disambiguation. Let’s see the configuration of a bean and its dependencies using annotations: For setter-based DI, the container will call setter methods of our class after invoking a no-argument constructor or no-argument static factory method to instantiate the bean. Let’s create this configuration using annotations: