Dependency Injection with @Autowired
@Autowired is used to automatically inject dependencies into a class. When you annotate a field, setter method, or constructor with @Autowired, Spring will attempt to find a matching bean in the application context and inject it into the annotated component. It is typically used when you have multiple beans of the same type, and Spring needs to determine which one to inject automatically.
Java
@Servicepublic class MyService { private final MyRepository repository; @Autowired public MyService(MyRepository repository) { this.repository = repository; } } /*This Java program defines a Spring service class named MyService. It relies on constructor-based dependency injection with the @Autowired annotation to inject a MyRepository dependency into the class. This allows the MyService component to use the functionality provided by MyRepository for data access or other related tasks. The @Service annotation marks the class as a Spring-managed service or component, making it available for use within a Spring application. In this example, the MyRepository bean is automatically injected into MyService.*/ |
Introducing @Qualifier
@Qualifier is used in conjunction with @Autowired to specify which exact bean should be injected when there are multiple beans of the same type in the application context.You use @Qualifier to provide a specific bean name or value to indicate which bean should be injected.
Java
@Servicepublic class MyService { private final MyRepository firstRepository; private final MyRepository secondRepository; @Autowired public MyService(@Qualifier("firstRepository") MyRepository firstRepository, @Qualifier("secondRepository") MyRepository secondRepository) { this.firstRepository = firstRepository; this.secondRepository = secondRepository; } } /*This Java code defines a Spring service class named MyService with two dependencies of type MyRepository. The @Autowired constructor is used for dependency injection, and @Qualifier annotations specify which specific beans to inject for each dependency. This code is a typical example of Spring's dependency injection mechanism for managing and wiring components in an application. Here, we use @Qualifier to differentiate between two MyRepository beans.*/ |
Spring – When to Use @Qualifier and @Autowired For Dependency Injection
In the world of Spring Framework, managing dependencies is a fundamental aspect of building robust and maintainable applications. Spring offers two primary annotations to facilitate dependency injection: @Autowired and @Qualifier. Understanding when and how to use these annotations is crucial for effective bean wiring .@Autowired and @Qualifier are both annotations used in Spring Framework to work with dependency injection, but they serve different purposes.
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