Guice

Guice is a lightweight dependency injection framework for Java developed by Google. It provides automatic wiring of dependencies through annotations and a simple API, enabling modular design with minimal configuration.

The core concepts are modules, bindings, and injectables. An Injector creates instances and satisfies dependencies. Modules declare bindings, for example mapping an interface to an implementation, or providing a factory. Dependencies are declared with @Inject on constructors, methods, or fields.

Guice supports scope annotations such as @Singleton to reuse instances; additional scopes are available through extensions (for example, servlet environments provide request and session scopes). It also offers provider methods using @Provides, assisted injection for factories, and AOP with MethodInterceptor.

Configuration is done in Java code (no XML), via modules. This makes the configuration tightly coupled with the code, but more type-safe and refactor-friendly than XML-based approaches.

Guice is used in various Java applications, including server-side applications and some Android projects. It is positioned as a lightweight alternative to heavier DI containers like the Spring Framework, emphasizing simplicity and speed.