How does autowiring work in Spring?

@Autowired
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Spring's autowiring takes care of injecting needed beans in your application by specifically matching types. Attach @Autowired to constructors, fields, or methods for dependency injection.

Example:

@Component
class Car {
  @Autowired
  private Engine engine; // Spring wires Engine here, just like car mechanics!
}

@Component
class Engine {} // Yes, this is a bean, and yes, it has nothing inside... just for the sake of an example!
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Key Point: With @Autowired, Spring manages beans and dependencies for you, minimizing the need for boilerplate code.

Spring's application context holds all the beans for you, just like a fancy coffee shop! By adding @Service to a class (like UserServiceImpl), it becomes a managed bean and Spring is ready to inject it anywhere you use @Autowired. Don't forget to have <context:component-scan> in your applicationContext.xml, thus telling Spring to scan classes and manage beans automatically—less XML juggling for you!

Faced with the tough choice of multiple beans of the same type, @Qualifier rolls up its sleeves and picks the right one. And if you're attached to the past, there's still support for XML-configurable autowiring or other annotations like @Inject and @Resource.

Now, a secret tip for you—@Autowired isn't the undefeated champion. With the newest releases of Spring, constructor injection doesn't even beg for an @Autowired annotation. The Spring container turns detective and wires through the constructor with the best matching parameters.