Spring Data JPA

谁践踏了优雅 2022-05-22 06:24 129阅读 0赞

# 前言 #

最近看springBoot中小例子时，看到了spring Data JPA,就简单了解一下。

# 什么是Spring Data JPA? #

JPA即Java Persistence API.JPA是一个基于O/R映射的标准规范。所谓规范即只定义标准规则（如注解、接口），不提供实现，软件提供商可以按照标准规范来实现，而使用者只需按照规范中的定义的方式来使用，而不用和供应商的实现打交道。JPA的主要实现由Hibernate、EclipeLink和OpenJPA等，意味着我们只要使用JPA来开发，无论哪一个开发方式都是一样的。

是Spring Data的一个子项目，通过提供基于JPA的Repository极大地减少了作为数据访问方案的代码量。

# 查询关键字 #

<table> 
 <tbody> 
 <tr> 
 <td>关键字</td> 
 <td>示例</td> 
 <td>同功能JPQL</td> 
 </tr> 
 <tr> 
 <td>And</td> 
 <td>findByLastnameAndFirstname</td> 
 <td>where x.lastname=?1 and x.firstname=?2</td> 
 </tr> 
 <tr> 
 <td>Or</td> 
 <td>findByLastnameOrFirstname</td> 
 <td>where x.lastname=?1 or x.firstname=?2</td> 
 </tr> 
 <tr> 
 <td>IsEquals</td> 
 <td>findByFirstname,findByFirstnameIs,findByFirstnameEquals</td> 
 <td>where x.firstname=1?</td> 
 </tr> 
 <tr> 
 <td>Between</td> 
 <td>findByStartDateBetween</td> 
 <td>where x.startDate between 1? and ?2</td> 
 </tr> 
 <tr> 
 <td>LessThan</td> 
 <td>findByAgeLessThan</td> 
 <td>where x.age &lt;?1</td> 
 </tr> 
 <tr> 
 <td>LessThanEqual</td> 
 <td>findByAgeLessThanEqual</td> 
 <td>where x.age &lt;=?1</td> 
 </tr> 
 <tr> 
 <td>GreaterThan</td> 
 <td>findByAgeGreaterThan</td> 
 <td>where x.age &gt;?1</td> 
 </tr> 
 <tr> 
 <td>GreaterThanEqual</td> 
 <td>findByAgeGreaterThanEqual</td> 
 <td>where x.age &gt;=?1</td> 
 </tr> 
 <tr> 
 <td>After</td> 
 <td>findByStartDateAfter</td> 
 <td>where x.startDate &gt;?1</td> 
 </tr> 
 <tr> 
 <td>Before</td> 
 <td>findByStartDateBefore</td> 
 <td>where x.startDate &lt;?1</td> 
 </tr> 
 <tr> 
 <td>IsNull</td> 
 <td>findByAgeIsNull</td> 
 <td>where x.age is null</td> 
 </tr> 
 <tr> 
 <td>IsNotNull,NotNull</td> 
 <td>findByAge(Is)NotNull</td> 
 <td>where x.age not null</td> 
 </tr> 
 <tr> 
 <td>Like</td> 
 <td>findByFirstnameLike</td> 
 <td>where x.firstname like ?1</td> 
 </tr> 
 <tr> 
 <td>NotLike</td> 
 <td>findByFirstnameNotLike</td> 
 <td>where x.firstname not like ?1</td> 
 </tr> 
 <tr> 
 <td>StartingWith</td> 
 <td>findByFirstnameStartingWith</td> 
 <td>where x.firstname like ?1(参数前面加%)</td> 
 </tr> 
 <tr> 
 <td>EndingWith</td> 
 <td>findByFirstnameEndingWith</td> 
 <td>where x.firstname like ?1(参数后面加%)</td> 
 </tr> 
 <tr> 
 <td>Containing</td> 
 <td>findByFirstnameContaining</td> 
 <td>where x.firstname like ?1(参数两边加%)</td> 
 </tr> 
 <tr> 
 <td>OrderBy</td> 
 <td>findByAgeOrderByLastnameDesc</td> 
 <td>where x.age =?1 order by x.lastname desc</td> 
 </tr> 
 <tr> 
 <td>Not</td> 
 <td>findByLastnameNot</td> 
 <td>where x.lastname&lt;&gt;?1</td> 
 </tr> 
 <tr> 
 <td>In</td> 
 <td>findByAgeIn(Collection&lt;Age&gt; ages)</td> 
 <td>where x.age in ?1</td> 
 </tr> 
 <tr> 
 <td>NotIn</td> 
 <td>findByAgeNotIn(Collection&lt;Age&gt; ages)</td> 
 <td>where x.age not in ?1</td> 
 </tr> 
 <tr> 
 <td>True</td> 
 <td>findByActiveTrue()</td> 
 <td>where x.active = true</td> 
 </tr> 
 <tr> 
 <td>False</td> 
 <td>findByActiveFalse()</td> 
 <td>where x.active = false</td> 
 </tr> 
 <tr> 
 <td>IgnoreCase</td> 
 <td>findByFirstnameIgnoreCase</td> 
 <td>where UPPER(x.firstname)=UPPER(?1)</td> 
 </tr> 
 </tbody> 
</table>

# 小结 #

望名知意，可以简化代码量，其实还有很多特性。