第一章，第一节，Spring Data JPA是什么

Spring Data JPA, part of the larger Spring Data family, makes it easy to easily implement JPA based repositories. This module deals with enhanced support for JPA based data access layers. It makes it easier to build Spring-powered applications that use data access technologies.

 

Spring Data JPA，Spring Data大家庭的一部分，使基于JPA的数据仓库变得更加容易实现，这个模块处理基于JPA的数据访问层的扩展支持，使构建基于Spring的使用数据访问层技术的应用变得更加容易。

 

Implementing a data access layer of an application has been cumbersome for quite a while. Too much boilerplate code has to be written to execute simple queries as well as perform pagination, and auditing. Spring Data JPA aims to significantly improve the implementation of data access layers by reducing the effort to the amount that's actually needed. As a developer you write your repository interfaces, including custom finder methods, and Spring will provide the implementation automatically.

 

过去的很长一段时间，实现一个应用的数据访问层显得很繁琐、笨重，必须写太多的模块代码来实现一个简单的查询、分页、校验，Spring Data JPA就是为了显著减少数据访问层的真正需要的代码的数量，作为一个开发者，你只需要写访问的接口，包括个性化的查找语句，Spring来替你自动实现。

 

Features

• Sophisticated support to build repositories based on Spring and JPA
• Support for Querydsl predicates and thus type-safe JPA queries
• Transparent auditing of domain class
• Pagination support, dynamic query execution, ability to integrate custom data access code
• Validation of @Query annotated queries at bootstrap time
• Support for XML based entity mapping
• JavaConfig based repository configuration by introducing @EnableJpaRepositories.

（ Querydsl是一个Java开源框架用于构建类型安全的SQL查询语句。它采用API代替拼凑字符串来构造查询语句。可跟 Hibernate 和 JPA 等框架结合使用。 ）

特性

• 构建基于Spring和JPA的数据仓库的精巧的支持
• 对Querydsl的支持，即类型安全的JPA查询
• 透明的模型类的校验
• 分页、执行动态查询、可集成个性化的数据访问代码
• 引导时对@Query注解进行验证
• 支持基于xml的实体映射
• 推荐使用@EnableJpaRepositories注解配置存储仓库