Spring Constructor Injection: Why is it the recommended approach to Dependency Injection?
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- เผยแพร่เมื่อ 2 มี.ค. 2022
- In this tutorial, you will learn why Constructor Injection is the recommended approach to dependency injection in Spring. To accomplish this you will learn some of the basics around Spring Beans, Application Context, Dependency (DI) Injection, and Inversion of Control (IoC).
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Finally someone digging more into theory. Often times Spring boot tutorials just telling you how to do it but not why. This is the first video I really find helpful, keep up the good work! Greetings from Germany.
Hello Germany 👋🏻 Thank you for the kind words. I'm glad you enjoyed the explanation.
@@DanVega What's the difference between these two ways you are instantiating the object of VideoRepository at following timestamps :
The way you have instantiated repository object at 15:20
v/s
The way you have instantiated repository object (using constructor DI) at 18:08
@DanVega I was little confused since whether the code of former timestamp also a constructor based dependency Injection ?
You're right. I've seen a couple of tutotials and they say: "You have to implement dependency injection, otherwise you'll get an exception". And the Spring Framework itself tells you to use a Bean for some class. But I'm wondering: Why do we have to do all this??? Here it is. BTW, my brother lives in Germany. :)
I searched a lot to understand why we are using certain stuffs in spring and I could only find it here.. everywhere it is just how to do and not why to do.. thank you so much
Thank you, I'm glad I am able to bring a different perspective and help out!
definitely learned a lot Dan! I’ve never seen test with autowired annotations. Usually its all using Mock annotations, please do a continuation of this on how to properly test that controller with constructor injection
Finally a high quality Spring tutorial!
can't wait to see more 🔥 this was so clear glad I found you
Thank you so much for the kind words!
Great video. All topics (beans, application context, injection, ioc) just happen to hit on many things I've been wondering about lately, considering myself still fairly new to Spring. Especially loved the clear explanations on the different kinds of injection, and WHY we want to favor constructor injection.
Thank you for the kind words, glad you enjoyed it!
It's All about why we use it and then it will be more clear and make scenes. Thank You a lot. Thumbs up for you.
Great Video Dan!
Found the channel via Spring Boot 2.6 video.
We need more videos like this one that explain Spring concepts in a practical manner - i am sure that many people are using Spring for many years but are still not aware why some things work like they do and why some choices have been made in the framework.
Anyway i had to learn this the hard way, in almost all of the projects we are using Field Injection, but there was use case when some specific functionality had to be tested and mocking was not an option, so i learned that "constructor" injection is the only way to do it properly.
Keep up the good work!
Thank you for the kind words and for taking the time to provide some feedback. It is very much appreciated.
I was using a lot of that stuff and had kind of an idea of why I was using it but your take is super simple, thank you, it was an incredible back to the basics
Glad this was helpful.
Took me about 2 hours to follow along taking notes and looking up definitions I didn't know, but man am I glad I did! I feel as though I have a solid base level understanding of Spring concepts after the video. Totally recommend this to everyone, your every sentence speaks volumes of your knowledge. Thank you and keep it up!
really good content! i always made constructor injection cause my lead told me to, but i never knew why. Thank you!
If you prefer the cleaner look of field injection, but don't want to give up the advantages of constructor injection, there is a way. Just declare the dependency final and use the Lombok annotation RequiredArgsConstructor on your class definition. Hope this helps someone.
Yes, I usually do this
So are you doing that so that the dependency is never null?I could not understand the point he made about the possibility that your dependency could be null if you use field injection
@@RAHUL-xy1ds Because you can't use field injection with final declared instance variables. This leads to a mutable field, which could also be changed to null. It's more or less an academical issue, but you can never guarantee that the injected field stays unchanged. With constructor injection instead, you can declare the field as final. This ensures that this field is immutable and can only be set once inside a constructor.
@@MCjusticejuice Oh alright...thank you so much...
How am I just finding about your content now?😭 your channel is a goldmine
Clear explanation of not only Constructor Injection, but also Dependency Injection in general.
Hi Dan, this is a great video, I have been a Spring dev for years, but this is such a nice clear explination. Really enjoying these videos that take small aspects of spring and expalined so well. Thank you
Glad you enjoyed it!
Discovered you recently Dan and I must say I am glad I did. I have subscribed and started watching some of your videos to help reinforce some of my understanding on things I picked up while working with Spring boot but not necessarily clear on everything. Very helpful sir...keep up the great work !! Greetings from Texas :)
Great video, thanks for your dedicated work to teach relevant and in-depth spring knowledge. We appreciate it!
Thank you for the kind words. I appreciate it 😊
I really like the way you explain all these things, you are explaining everything very well and simple! Good video!
A nice set of videos Dan. I really like the precursory problem statement you share in the beginning few seconds of the video, then you go with your short, self intro and then stepping into the full video. Unique style and I like the way you present the stuff. Though I am a subscriber of your newsletter and the TH-cam channel, I am now watching all the videos of yours one by one now :) Keep rocking and thank you for all the knowledge you share!
Wow thank you so much for the kind words my friend.
This is exactly I was looking for as a dotnet developer switching over to Kotlin + spring. All the other tutorials didn’t explain how things were working under the hood. Cheers!
simple and clean explanation, thank you so much, now I can say that I understand what is DI ,IOC
Happy that I stumbled upon your channel Dan. you are super awesome 😎👍🏼
Your tutorial was so helpful to me, i definitely learned it. Thanks a lot
Thanks. Great tutorial
really clear to understand.
thanks Dan! 😀
very interesting and really clear explanation of why we use these concepts .. thank you :D
great stuff...again and again. keep it up Dan
Very nice explanation! Spring internals are super interesting
Thank you!
Really great!!! Thank you.
Thank you Dan!
Now I understand DI and IOC
Thanks for the easy explanation
Great tutorial.. great explanation!
Very informative, love your channel. Keep it up
extremely helpful!! thanks!!
loved the explanation
Couldn't stop commenting. Lucid explanations ❤
Glad you enjoyed it 🤩
Great explanation!!
Thanks Dan.
Nice content
Really great!! Thank you. :)
Mannnn so useful please keep going we need more content like these, and please some docker and kubernetes with spring tutorials would be great
Thanks Michel, appreciate the continued support and feedback.
wonderful explanation. I was looking for such explanation for a long time :)
Thank you Sachin. Glad it helped you out!
Junior and some middle devs mostly cares about the count of code lines and think less == good. Senior and lead devs cares about code quality, readability and security and don't care about lines of code :)
Video was incredible Dan, thanks for making such an effort on explaining all the little details. A recommendation I have is to use the same microphone while talking in-front of the camera as the one you are using when writting code (the second microphone is way better quality in my opinion), because the difference between them is very clear and could irritate some viewers slightly.
perfection!
This is gold... revised before an interview...lol
thanks , great examples :D
thank you so much!
Loved it
thank you!
Great Content.
Great talk 👍👍
It became much clearer why I should create classes that way
Thanks a lot
Glad to hear that
Thank you, it was a good video, actually, I learned about why the Constructor injection is better
Thanks a lot!
You're welcome!
great keep making such useful and code based videos bro, tnx
You are welcome
Great explanation
Glad it was helpful!
Thanks for the video. A very simple and easy explanation of a concept that I thought is quite difficult. Turns out, it's not!
Yes! So glad that it helped clear up this topic for you Vitali
The better way to learn is to understand thank you :-)
An interviewer asked me this question and my answer was "idk it's just how I was taught 😎" . I didn't get the job 🤣🤣. So this video is appreciated.
Sorry to hear you didn't get the job, hope it all worked out for the best. I have been in the same position. I take those as learning opportunities for the next one.
@@DanVega absolutely, thanks again Dan.
This is the first perfect answer
Your videos on a level that explains things so well, great stuff, as always 👍Keep up the good work, you're helping me so much! Great content, as always, so clear and well structured, Dan is the best instructor ever! Deep dive 27:41 please 😊
This video justcame up the right time. I always have some problems understanding how to connect beans the right way, also with JPA or other frameworks, maybe mixed with streams/collections and debugging(!) them correctly.
Questions:
- at 10:55 - why does Sping identifies the bean with lower Case? Is it only for creating a unique identifier/name internally or is there another reason?
- What theme you use for IntelliJ?
Guess he had explained it along the way that Spring Framework uses the camelCase notation for the Beans.
Thank you very much for the cool explanation; is there a way to use constructor injection when there are more than one dependencies
Make more videos Sir. Thank you for the content!!
nice video
Thanks
Love
Thats really a great explanation,
I have one more query: does constructor injection also use reflections internally?
No. Field Injection uses reflection while constructor and setter injection do not.
Hello!
How does the private final field, and the loaded constructor affect Jpa? -- would a second empty controller be required?
thanks for the excellent explanation!
IntelliJ Ultimate has the Spring initializer built in when you create a new project
Hello Dan, thanks for this highly insightful video!
This leaves me with a rather rudimentary question.
Since it is fully possible to code constructor injection (with arguments) without the Spring Framework (since this is how I've been doing dependency in my non-Spring code bases like AWS Lambdas), what are the other benefits that are provided by Spring, purely from the standpoint of constructor injection? In the grand scheme of things, agreed that Spring does a lot more under the hood but just wanted to understand the *real* relevance of Spring in case of contructor-injection-based dependency management. Thanks in advance for your time on this!
What's the difference between these two ways you are instantiating the object of VideoRepository at following timestamps :
The way you have instantiated repository object at 15:20
v/s
The way you have instantiated repository object (using constructor DI) at 18:08
@DanVega I was little confused since whether the code of former timestamp also a constructor based dependency Injection ?
I thought that type of injection depends on architecture. If I want to change behavior of video-controller in runtime (without creating another video-controller with required behavior), it's necessary to use injection with setters. If I require immutable bean with all not-null dependencies, I need to use injection with constructor.
When doing DI, what is the lifecycle of DI item, is it always be singlton in spring ?
Never knew Mark Knopfler is high on spring as well
why you have color in your output console? i have to add the line in the .properties; spring.output.ansi.enabled=Always
How do you do to do it by default?
22:39 how videoRepository can be null with autowired if it is being managed by spring 🤔
Hi Dan are u using vs code?if yes which dependencies to install to get auto suggestions.
he is using intellij idea
22:38 how can be VideoRepository null if it’s being managed by Spring.
nice plugin suggestion. What is that?
tabnine AI
Autowired is useful when there is circular dependency.
You must be doing something wrong in the first place to land in that area.
can I make the repository an interface? how would spring resolve it? how to bind an implementation into an interface in the way of spring?
You could make it an interface... I'm not quite sure what you're asking though? Do you have an example?
I still don't get what Inversion of Control is. Inverting control from what? Like inverting the creation of object from a class to container?
Exactly. Instead of you having to create an instance and supply a dependency you are asking the framework to handle that for you.
@@DanVega ok i got it thanks for the response. So probably the reason why Martin Fowler want to call it Dependency Injection instead of IoC from his 2004 article about Spring and PicoContainer, because the term is kinda confusing.
If you know the terms declarative and imperative that might help to understand IOC in general. Even with the spring framework, at least in the old days before the annotations were added, the dependencies were declared in an xml file that the operations team could modify as needed without having to recompile the application. Only I doubt that it was done that way in practice very often. When coupled with external property configuration, using annotations to declare the dependencies the way Dan explained works well for most applications.
What is Giving u all those suggestions in intellij
21:00 why @AutoWired is bad
The autowired annotation isn't bad but field injection is. You can do a search on that but tldr; don't use it.