Spring is a layered Java/J2EE application framework, based on code published in Expert One-on-One J2EE Design and Development by Rod Johnson (Wrox, 2002).
* Generic abstraction layer for transaction management, allowing for pluggable transaction managers, and making it easy to demarcate transactions without dealing with low-level issues. Generic strategies for JTA and a single JDBC DataSource are included. In contrast to plain JTA or EJB CMT, Spring's transaction support is not tied to J2EE environments.
* JDBC abstraction layer that offers a meaningful exception hierarchy (no more pulling vendor codes out of SQLException), simplifies error handling, and greatly reduces the amount of code you'll need to write. You'll never need to write another finally block to use JDBC again. The JDBC-oriented exceptions comply to Spring's generic DAO exception hierarchy.
* Integration with Hibernate, JDO, and iBATIS SQL Maps: in terms of resource holders, DAO implementation support, and transaction strategies. First-class Hibernate support with lots of IoC convenience features, addressing many typical Hibernate integration issues. All of these comply to Spring's generic transaction and DAO exception hierarchies.
* AOP functionality, fully integrated into Spring configuration management. You can AOP-enable any object managed by Spring, adding aspects such as declarative transaction management. With Spring, you can have declarative transaction management without EJB... even without JTA, if you're using a single database in Tomcat or another web container without JTA support.
* Flexible MVC web application framework, built on core Spring functionality. This framework is highly configurable via strategy interfaces, and accommodates multiple view technologies like JSP, Velocity, Tiles, iText, and POI. Note that a Spring middle tier can easily be combined with a web tier based on any other web MVC framework, like Struts, WebWork, or Tapestry.