How are GoF patterns used in real-world frameworks?

GoF patterns appear throughout major frameworks. In Spring (Java): Singleton (all beans are singletons by default), Factory Method (BeanFactory), Proxy (@Transactional, AOP), Template Method (JdbcTemplate, RestTemplate), Observer (ApplicationEvents). In Laravel (PHP): Facade pattern is prominently used for the service container, Factory for model factories, Observer for Eloquent model events, Decorator in middleware pipeline. In React: Observer (state and props reactivity), Composite (component tree). In Java Collections: Iterator (all collection traversal), Flyweight (String pool), Decorator (I/O streams). Recognizing patterns in frameworks helps you understand and use them more effectively.