Spring

Spring is a lightweight inversion of control and aspect-oriented container framework.
- lightweight: size/overhead, and nonintrusive, app doesn't have dependencies on Spring specific classes
- inversion of control: object are passively given the dependencies instead of creating or looking for dependencies. beans loosely couple through interface.
- aspect-oriented: enable cohesive development by separating application business logic from system services (commonly referred to as cross-cutting concerns because they tend to cut across multiple components) such as auditing and transaction mgr.
- container: contains and managers the life cycle and config of app objects, creating associations between collaborating components (wiring beans)
- framework: config and compose complex app from simple component.

Common implementations of ApplicationContext:
- ClassPathXmlApplicationContext: load context definiton as xml from classpath
- FileSystemXmlApplicatonContext: load from file system
- XmlWebApplicationContext: load from xml contained within a web application