Constructor Injection
Constructor injection is a dependency injection technique where dependencies are provided to a class through its constructor parameters. This ensures that an object is fully initialized with all required dependencies before it can be used, promoting immutability and explicit dependency declaration. It is a core pattern in dependency injection frameworks and object-oriented design for managing object creation and reducing coupling.
Developers should use constructor injection when building testable, maintainable applications, particularly in frameworks like Spring (Java) or ASP.NET Core, as it makes dependencies explicit and facilitates unit testing by allowing easy mocking. It is ideal for scenarios requiring strong immutability guarantees, such as in service classes or components where dependencies should not change after instantiation, ensuring predictable behavior and reducing runtime errors.