Spring @Autowired tricks

#spring #java #tutorial #springboot

Introduction

As we know Spring framework is a dependency injection framework that keep tracks from your classes and whenever you want an instance spring will provide that for you.

By Annotating your classes with @Service or @Component Spring at runtime will create instances from these classes and wherever you want an object from them you just use @Autowired so that spring knows that you need an object here.

Some Magic

But there is some tricks may add value to your code or make code cleaner , as image below we have IMove interface with 2 different implementations for it.

you can use @Autowired with List of IMove and spring will get all interface implementations and put them into the list , or you can use Map of String and IMove and spring will construct a map with service name as a key and an object of this service as a value like below image.

You can benefit from this for an example if you have a multiple validation logic over some value you can use @Autowired with List trick to group validators based on type and fire them in a much clean way like below images.

Or in a different way you can use Map to fire specific logic based in some parameter value like below image.

Notes

just be careful when you have this setup and try in inject one object from the interface , application will not run because Spring will be confused as it will not know which implementation have to use to fulfill this injection , you can solve this situation with @primary or @Qualifier like this.