Dependency Injection & Inversion of Control in Spring Tutorial #DI #IOC #Spring #SpringBoot #Java

If you want to master Spring and Spring Boot, you have to be a master of Dependency Injection and Inversion of Control in Spring. In this Spring IoC & DI tutorial, we'll look at exactly what Inversion of Control is in Spring, and how Spring Dependency Injection works with the Spring IoC container.

This Spring tutorial looks only at the core Spring Framework, or more specificially, the Java classes associated with the spring-context starter. We don't even using Spring Boot, but instead just core Spring framework classes to access the ApplicationContext, user Autowired and Component annotations, and see how Inversion of Control and Dependency Injection works in Spring.

A full tutorial is over on TheServerSide.

The following is just some AI generated junk to capture keywords...

Inversion of Control (IoC) and Dependency Injection (DI) are core principles of the Spring Framework that help manage object creation and dependencies in a flexible and decoupled manner.

Inversion of Control (IoC) refers to a design pattern where the control of creating and managing objects is transferred from the application code to a container or framework, in this case, the Spring IoC container. Instead of objects creating their dependencies, the IoC container manages the lifecycle of objects and their dependencies. This inversion allows for more modular, testable, and maintainable code because it decouples the implementation details from the control flow.

Dependency Injection (DI) is a specific way to implement IoC, where an object’s dependencies are “injected” into it, rather than the object creating them itself. In Spring, DI can be achieved through constructor, setter, or field injection, depending on how the dependencies are supplied to the object. This approach allows objects to be loosely coupled and easily interchangeable, promoting a flexible architecture.

Benefits of IoC and DI in Spring:
Decoupling: By outsourcing the management of dependencies, classes are not tightly bound to their dependencies, making it easier to change or replace them without impacting other parts of the application.

Easier Testing: DI allows for easy substitution of dependencies with mock objects during testing, enabling effective unit testing.

Improved Code Reusability: Components can be reused in different contexts without modification since they do not manage their dependencies directly.

Configuration Flexibility: Dependencies and object configurations are managed externally, often through XML, Java annotations, or Java configuration classes, making it simple to adjust application behavior without altering code.

Better Maintainability: The decoupled nature of components leads to cleaner, more maintainable code, as dependencies can be managed and updated centrally.

IoC and DI in Spring promote a clean, modular architecture that enhances flexibility, testability, and maintainability, making them fundamental to modern Spring-based applications.

[arkhane]

I use Spring for developing web applications, and Spring Boot configures dependency injection out of the box. With your video, I finally understood how it works 'in simple terms.' Thank you!

[housemajaliwa]

Loved it. Thank you. Just got into Spring. Been wanting to wrap my head around IoC and DI for a while now.

[abdurrahmanseyidoglu]

Thank you so much!
I just have one small request: it would be great if you could increase the video quality to 1080p or enlarge the font size a bit, as it was a little difficult to read on my end

[AozenDreyar]

when a class is passed into a constructor what exactly happens internally? does it make an instance of the class? when we pass the class are we passing the class itself or an object of the class ( since java is pass by copy i think object is passed) however in terms of initialization which constructor is passed and is it passed at all and will the values be initialized in the class itself or when it is passed as an object to the other class? also in practice it would all be the same as saying Potato potato = new Potato() inside another class and then we use the constructor that class has for initialization and we done right?

[dig]

I've been relearning java spring/springboot at the moment and realized I severely lacked depth. I find your channel very informative and clear compared to others but I still get confused how things work. Putting down here in points my understanding from the video:

1. Spring/Spring is the framework that has IoC container and use DI to manage dependencies.
2. If there are class A with dependency of class B, the framework will initialize class A and class B at the same time, ignoring the dependencies and then only supplies the dependency via DI at runtime?

[fikrilhadadramadhani]

why does this video only have 42 likes and less than a billion

[alpharetta]

Doesnt Game class need an annotation on it ?

[statitik]

from 20:00 onward: *this* is exactly what i was stating yesterday for more than 2 hours but you didn't seem to grasp this very basic comment at all. I literally had written:
"any time you pass an object the class is dependent on and does not create it you are passing a dependency!"
whereupon you claimed:

"Again, you keep asserting that any time you pass an argument to a constructor it is injection. That demonstrates a complete and total misunderstanding of what DI is."

You don't know what you are teaching, lol!
Your game class is DEPENDENT on score; but does not create score itself. Thus, the dependency is injected from outside. This is done either through constructor, or in the case of java spring annotation.

But what spring does for you when you retrieve a DI-container managed class instance is literally nothing but get all annotated fields per reflection, look into its DI-container whether an instance of Score exists and assigns the value it has to the annotated field .. again .. per reflection.

Yet, if you did not use the spring-framework, and you would create Score in the main class alongside Game and passed the instance of Score to the Game via constructor, you literally would inject a dependency. But in this case, the spring framework does this for you.

Why did you argue with me over this simple observation? Dont you know how DI-container work internally?
Emberassing!