OSGi
OSGi (Open Service Gateway Initiative) is a Java-based modular framework that enables dynamic component management in applications. It provides a standardized environment for building modular, reusable, and dynamically deployable software components called bundles. OSGi allows applications to install, start, stop, update, and unload modules at runtime without requiring a restart.
Developers should learn OSGi when building large-scale, modular Java applications that require dynamic updates, such as enterprise systems, IoT platforms, or embedded devices. It is particularly useful in scenarios where applications need to manage dependencies, versioning, and lifecycle of components independently, enabling better scalability and maintainability. For example, it's widely used in Eclipse IDE plugins, automotive software, and home automation systems.