First, what is Spring
Spring is a framework
The core idea of IoC, AOP
Simplify enterprise development, to help separate the dependencies between objects
IoC: Inversion of Control Inversion of Control
DI: dependency injection: Dependency Injection
AOP: Aspect Oriented Programming Aspect Oriented Programming
Two, Spring can solve the problem
Decoupling the application, simplifying the development process
AOP support
Declarative transaction
Integrated Junit4
Easy integration of a variety of excellent open source framework
The difficulty of reducing the use of JavaEE API
Three, Spring composition
