What does @inject do in Java?

Injectable constructors are annotated with @Inject and accept zero or more dependencies as arguments. @Inject can apply to at most one constructor per class. @Inject is optional for public, no-argument constructors when no other constructors are present. This enables injectors to invoke default constructors.

How do you inject beans in the Spring?

In Spring Boot, we can use Spring Framework to define our beans and their dependency injection. The @ComponentScan annotation is used to find beans and the corresponding injected with @Autowired annotation. If you followed the Spring Boot typical layout, no need to specify any arguments for @ComponentScan annotation.

How do you auto inject a field into a bean?

C. By using both the @Autowired and the @Qualifier spring annotations. D. By using the @Autowired annotation and naming the field with the bean name.

What is @inject in Spring?

@Inject annotation is a standard annotation, which is defined in the standard “Dependency Injection for Java” (JSR-330). Spring (since the version 3.0) supports the generalized model of dependency injection which is defined in the standard JSR-330.

What are the different types of bean injection?

Broadly and historically, it supports two types of bean injection:

  • Constructor Based Bean Injection.
  • Setter Based Bean Injection.

Why field injection is not recommended?

The reasons why field injection is frowned upon are as follows: You cannot create immutable objects, as you can with constructor injection. Your classes have tight coupling with your DI container and cannot be used outside of it. Your classes cannot be instantiated (for example in unit tests) without reflection.

What is the scope of a bean in Java?

Scopes a single bean definition to any number of object instances. Scopes a single bean definition to the lifecycle of a single HTTP request; that is each and every HTTP request will have its own instance of a bean created off the back of a single bean definition.

Why we use @inject in Spring?

@Inject is part of the Java CDI (Contexts and Dependency Injection) standard introduced in Java EE 6 (JSR-299), read more. Spring has chosen to support using the @Inject annotation synonymously with their own @Autowired annotation. So, to answer your question, @Autowired is Spring’s own annotation.

Is Autowired a field injection?

In field-based dependency injection, fields/properties are annotated with @Autowired . Spring container will set these fields once the class is instantiated. As you can see, this is the cleanest way to inject dependencies as it avoids adding boilerplate code and there is no need to declare a constructor for the class.

Why constructor injection is better than field injection?

At this related question there are some valid arguments why to use injection via constructor instead of injection via field. It boils down to the advantage that you can use initialization via constructor also in non-CDI environment i.e. Unit Test, without the need to add more complex logic.

Are beans singletons?

Singleton is the default scope for a Bean, the one that will be used if nothing else is indicated. This scope implies that Spring container will create an only shared instance of the class designated by this bean, so each time the Bean is required the same object will be injected.