Spring Dependency Injection Concepts
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Questions and Answers

What is the purpose of the @SpringBootApplication annotation in the Spring framework?

  • To indicate a class as a configuration source.
  • To enforce dependency injection only via constructors.
  • To specify the base packages for component scanning. (correct)
  • To declare a class capable of handling web requests.

    • Which of the following is a correct step in the Setter Injection process?

  • Create setter method(s) in your class for injections. (correct)
  • Remove all existing methods before defining new injections.
  • Create constructor methods in your class for injections.
  • Inject dependencies directly in the class constructor.

    • In the context of Spring, what does component scanning refer to?

  • The configuration of network components within the application.
  • The process of searching for classes annotated with @Component. (correct)
  • The activation of the Spring Boot application.
  • The manual registration of services in the application context.

    • Which type of injection involves invoking setter methods for injecting dependencies?

    <p>Setter Injection</p> Signup and view all the answers

    What key characteristic differentiates Constructor Injection from Setter Injection?

    <p>Constructor Injection provides a strong guarantee for dependency immutability.</p> Signup and view all the answers

    When is constructor injection typically recommended?

    <p>When there are required dependencies</p> Signup and view all the answers

    Which method of dependency injection is best suited for optional dependencies?

    <p>Setter injection</p> Signup and view all the answers

    What does Spring do during the autowiring process?

    <p>Injects dependencies automatically by type</p> Signup and view all the answers

    In the provided example, what is non-existent in Spring's approach when injecting a Coach implementation?

    <p>Spring scans for @Components within specified packages</p> Signup and view all the answers

    What does the @Component annotation signify in a Spring application?

    <p>It marks the class as a Spring Bean.</p> Signup and view all the answers

    What would be the first step in the development process for constructor injection?

    <p>Define the dependency interface and class</p> Signup and view all the answers

    What is the purpose of the getDailyWorkout() method in the Coach interface?

    <p>To provide daily workout routines.</p> Signup and view all the answers

    What is the primary benefit of using setter injection?

    <p>Provides flexibility for optional dependencies</p> Signup and view all the answers

    In the DemoController class, which annotation is used for dependency injection?

    <p>@Autowired</p> Signup and view all the answers

    Which option describes a key concept of how Spring identifies classes during autowiring?

    <p>By matching types, either class or interface</p> Signup and view all the answers

    If a class has only one constructor, what is the requirement for using the @Autowired annotation?

    <p>It is optional.</p> Signup and view all the answers

    Which component in the provided example is responsible for returning the workout details?

    <p>DemoController</p> Signup and view all the answers

    What is returned by the getDailyWorkout() method in the CricketCoach class?

    <p>Practice fast bowling for 15 minutes.</p> Signup and view all the answers

    What does the DemoController class manage?

    <p>Web services and REST endpoint responses.</p> Signup and view all the answers

    Which of the following statements is true regarding Spring Beans?

    <p>They are regular Java classes managed by the Spring container.</p> Signup and view all the answers

    Which package contains the Coach interface and the CricketCoach implementation?

    <p>com.luv2code.springcoredemo</p> Signup and view all the answers

    What does the annotation @Autowired indicate in the DemoController class?

    <p>It injects the specified dependencies into the class.</p> Signup and view all the answers

    What will the bean scope of the CricketCoach class be based on the annotation?

    <p>Singleton</p> Signup and view all the answers

    Which of the following scopes allows multiple instances of a bean to be created for each request to the container?

    <p>Prototype</p> Signup and view all the answers

    In the DemoController, why are two references to the same Coach bean being injected?

    <p>To ensure that both references share the same instance of the bean.</p> Signup and view all the answers

    What does the 'session' scope imply about a bean in a web application?

    <p>The bean is created once per HTTP web session and shared within that session.</p> Signup and view all the answers

    What is a primary benefit of using Spring for enterprise applications?

    <p>It simplifies database transactions.</p> Signup and view all the answers

    Which annotation enables Spring Boot's auto-configuration support?

    <p>@SpringBootApplication</p> Signup and view all the answers

    What does the @ComponentScan annotation do in a Spring Boot application?

    <p>It enables scanning of all components within the same package and sub-packages.</p> Signup and view all the answers

    What happens if a Spring Boot application is not located in the base package?

    <p>Only the main application package and its sub-packages will be scanned.</p> Signup and view all the answers

    Which of the following features does Spring provide for web applications?

    <p>REST APIs and Web MVC.</p> Signup and view all the answers

    What is the result of the SpringApplication.run() method in a Spring Boot application?

    <p>It runs the application context and registers all beans.</p> Signup and view all the answers

    Which of the following does NOT describe a feature of Spring Boot?

    <p>Manual bean management.</p> Signup and view all the answers

    What is a common pitfall when organizing Spring Boot applications?

    <p>Placing application classes in different directories.</p> Signup and view all the answers

    In a Spring Boot application, what does the term 'component scanning' refer to?

    <p>The automatic discovery and registration of beans in the application context.</p> Signup and view all the answers

    What is the role of the @Configuration annotation?

    <p>It indicates that a class contains bean definitions.</p> Signup and view all the answers

    What is the significance of using @Bean in a Spring Boot application?

    <p>It allows bean methods to be registered within a configuration class.</p> Signup and view all the answers

    What will NOT happen when using the @SpringBootApplication annotation?

    <p>Disables component scanning.</p> Signup and view all the answers

    When defining a main class for a Spring Boot application, the structure should include which of the following?

    <p>A public static main method.</p> Signup and view all the answers

    Which statement about Spring's component scanning is accurate?

    <p>It can scan all packages from the location of the main class.</p> Signup and view all the answers

    Study Notes

    Constructor Injection

    • Use constructor injection when your dependencies are required.
    • Considered the first choice by the Spring.io development team.

    Setter Injection

    • Use setter injection when your dependencies are optional.
    • If a dependency is not provided, your application can provide reasonable default logic.

    Spring Autowiring

    • Spring uses autowiring for dependency injection.
    • Spring searches for classes matching by type, either class or interface.
    • Spring automatically injects the matching class.

    Autowiring Example

    • Spring searches for classes annotated with @Component.
    • If a class implements the Coach interface, Spring injects it.
    • For example, Spring injects CricketCoach if it implements the Coach interface.

    Example Application

    • A web browser requests /dailyworkout from the DemoController.
    • The DemoController gets the getDailyWorkout() from the injected Coach.
    • The Coach implementation (CricketCoach) provides the daily workout, "Practice fast bowling for 15 minutes".

    Development Process - Constructor Injection

    • Define the dependency interface and class: Create the Coach interface and CricketCoach class, annotating the latter with @Component.
    • Create the Demo REST Controller: Create the DemoController class annotated with @RestController.
    • Create a constructor in your class for injections: Add a constructor to DemoController and inject the Coach dependency using @Autowired.
    • Add @GetMapping for /dailyworkout: Add the @GetMapping annotation to the relevant method in DemoController to define the endpoint for the daily workout.

    @Component Annotation

    • The @Component annotation marks a class as a Spring bean. A Spring bean is a regular Java class managed by Spring.
    • @Component makes the bean available for dependency injection.

    Spring for Enterprise Applications

    • Spring is designed for enterprise-level, real-time applications.
    • Spring offers features like database access, transactions, REST APIs, web MVC, security, and more.

    Component Scanning

    • Spring scans Java classes for annotations like @Component and automatically registers the beans in the Spring container.

    Java Source Code

    • Spring Boot uses the main application class (e.g., SpringcoredemoApplication) with the @SpringBootApplication annotation.
    • @SpringBootApplication enables auto-configuration, component scanning, and additional configuration.

    Annotations

    • @SpringBootApplication consists of:
      • @EnableAutoConfiguration: Enables Spring Boot's auto-configuration support.
      • @ComponentScan: Enables component scanning of the current package and its sub-packages recursively.
      • @Configuration: Enables registration of extra beans with @Bean or importing other configuration classes.

    Bootstrap your Spring Boot Application

    • The main method in the Spring Boot application class bootstraps the application.
    • Spring creates the application context and registers all beans.
    • It starts the embedded server (like Tomcat).

    More on Component Scanning

    • Spring Boot automatically scans the package of the main Spring Boot application class and its sub-packages.
    • To scan other packages, explicitly list the base packages to scan in @SpringBootApplication.

    Common Pitfall - Different Locations

    • Spring Boot does not automatically scan packages outside the main Spring Boot application class package and its sub-packages.

    Setter Injection

    • Setter Injection injects dependencies by calling setter methods on the class.

    Spring Injection Types

    • There are two primary injection types in Spring:
      • Constructor Injection: Occurs during the initialization of the bean.
      • Setter Injection: Occurs later in the bean lifecycle, after the bean has been initialized.

    Explicitly Specify Bean Scope

    • The @Scope annotation can be used to explicitly define the scope of a bean.
    • ConfigurableBeanFactory.SCOPE_SINGLETON is the default scope, meaning only one instance of the bean is created and shared across the application.

    Additional Spring Bean Scopes

    • singleton: Creates a single shared instance of the bean, the default scope.
    • prototype: Creates a new bean instance for each container request.
    • request: Scoped to an HTTP web request, only used for web applications.
    • session: Scoped to an HTTP web session, only used for web applications.
    • global-session: Scoped to a global HTTP web session, only used for web applications.

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    Related Documents

    02-spring-boot-spring-core.pdf

    Description

    This quiz covers key concepts of dependency injection in Spring, focusing on constructor and setter injection. It also explains how Spring uses autowiring to manage dependencies automatically, along with an example application. Test your understanding of these essential Spring frameworks’ features.

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