30.5.2. Dependency Injection (DI)

Try these first

1. 1.

   What does Dependency Injection do?

   Hint

   Think about how it contrasts with a class creating its own dependencies.

2. 2.

   Which annotation is typically used in Field Injection?

   Hint

   This annotation helps the framework know which dependencies to inject.

3. 3.

   What is the main advantage of Dependency Injection?

   • A. Increased coupling
   • B. Improved modularity
   • C. Reduced testability

   Hint

   Think of how you might change a part of the code without affecting others.

4. 4.

   True or False: Field Injection requires explicit constructors.

   • True
   • False

   Hint

   Consider whether constructors are needed when dependencies are injected directly.

5. 5.

   Create a simple class structure using Dependency Injection. Define a class Car that has a dependency on Engine. Illustrate with both Constructor and Setter Injection, and explain when each approach is preferable.

   Hint

   Use a constructor for things that must exist and setters for those that can wait.

6. 6.

   Discuss how Dependency Injection can lead to better unit testing practices. Provide an example scenario where DI improves the testability of a class.

   Hint

   Think about how you would isolate a class from its dependencies while testing.