DIContainer

A dependency injection container, commonly referred to as a DI container, is a framework or library that implements the dependency injection pattern by constructing and wiring up objects and their collaborators automatically. It manages object lifetimes and resolves dependencies, enabling inversion of control between components.

A DI container stores registrations mapping service contracts (such as interfaces or abstract classes) to concrete implementations. It supports various injection strategies, including constructor injection, property injection, and method injection, and it can manage object lifetimes through scopes such as transient, scoped, or singleton. Registrations can be performed via code configuration or, in some ecosystems, declarative sources.

At runtime, client code requests services from the container, which builds the requested object graph by recursively resolving dependencies. This decouples components from concrete implementations, improves testability by enabling easy substitution of test doubles, and centralizes configuration and wiring.

Common features include auto-resolution of dependencies through reflection or source generation, support for open generics, factory delegates, and interception for cross-cutting concerns like logging or transaction management. Performance considerations include caching of resolved graphs to reduce reflection overhead, and circular dependency handling.

DI containers are central in many modern frameworks. Java ecosystems feature containers such as Spring and Guice, while .NET ecosystems include Autofac, Ninject, StructureMap, and the built-in Microsoft.Extensions.DependencyInjection. Other languages have analogous tools that implement inversion of control.

DI containers originated from the dependency injection and inversion of control patterns in software design. They are related to service locators but typically differ in how dependencies are obtained. See also inversion of control, dependency injection.