@Lazy defers bean instantiation until it's first requested, overriding the default eager initialization behavior of singleton beans.

BeanFactory is the basic container, ObjectFactory is for lazy bean retrieval, and FactoryBean allows custom bean creation logic. All represent factory patterns in Spring.

PropertyPlaceholderConfigurer (or @PropertySource in modern Spring) enables externalization of configuration by replacing ${property.name} placeholders with actual values from properties files.

Spring provides multiple mechanisms for initialization: @PostConstruct, InitializingBean interface, and initMethod in @Bean definition. All are equally valid.

@Component is applied to classes making them beans automatically. @Bean is applied to methods in @Configuration classes, giving explicit control over bean creation.

When multiple beans match the injection point, Spring throws an exception unless @Primary is used to indicate the preferred bean or @Qualifier specifies which bean to inject.

Spring supports singleton, prototype, request, session, application, and websocket scopes. 'Eternal' is not a valid scope in Spring Framework.

ApplicationContext is the core container that instantiates, configures, and manages beans. It also resolves dependencies and manages bean lifecycle.

@Component, @Service, @Repository, and @Controller are all stereotype annotations that mark classes as Spring Beans. @Bean is used for method-level bean definition.

Constructor injection enforces required dependencies and creates immutable objects; setter injection allows optional dependencies and partial initialization.