Deciphering Dependency Management — Exploring @Qualifier and @Primary Annotations in Spring
Introduction
The Spring framework’s ‘Inversion of Control’ (IoC) container handles a plethora of responsibilities, including managing dependencies between classes. This article will go over two key Spring annotations, @Qualifier and @Primary, and how they streamline dependency management.
Inversion of Control (IoC) and Dependency Injection (DI)
Before diving into @Qualifier and @Primary, let’s briefly revisit IoC and DI concepts, the backbone of the Spring framework. IoC is a design principle that inverts the flow of control compared to traditional procedural programming, i.e., rather than the application calling the frameworks, the frameworks call the application. DI is an incarnation of IoC, where the dependencies are injected into the objects that need them.
Spring’s IoC container facilitates DI, reducing the need for boilerplate code and promoting a clean, decoupled architecture. However, there may be scenarios where multiple beans of the same type exist, leading to ambiguity during autowiring. This is where the @Qualifier and @Primary annotations come to our rescue.
