Spring: What is Spring Data?

是什么？好处坏处是什么？原理是什么（为什么有那么些好处坏处？）

是什么？
It is a high level springsource project whose purpose is to unify and ease the access to different kinds of persistence stores. both Relation DB and Non-relational DB.
it is to provide a consistent programming model for Data access no matter what underlying data store is. it makes the data acess on relational DB and non relational DB, map-reduce frameworks and cloud-based data services.

好处是什么？
it support for transparent auditing(like created and last changed)
easy spring integration via Java Config and custom XML name spaces.
Advanced integration with Spring MVC controllers.
Experimental support for cross-store persistence.

Main Modules:
Spring Data commons
Spring Data JDBC
Spring Data JPA
Spring Data Redis
Spring Data MongoDB
Spring Data Rest