There are two central concepts that summarize what Spring does. One is dependency injection and the other is aspect oriented programming (AOP). For someone learning Spring,these two concepts bring about the most confusion.


Dependency injection
Dependency injection or Inversion of control is based on a best practice technique (design pattern). This technique allows a part of application to be changed without causing problems in other areas of the application. A design is inflexible unless it cannot be easily adapted


Aspect Oriented Programming (AOP)
AOP – reduces duplication among classes
Interceptors make it easy to add before and after methods in code snippets.
Useful for caching,logging and security
EHCache,Performance/Tracing interceptors
Acegi for security