springboot 整合jpa一

àì夳堔傛蜴生んèń 2022-04-23 13:14 301阅读 0赞

# jpa 概述 #

全称Java Persistence API，通过JDK 5.0注解或XML描述对象－关系表的映射关系，并将运行期的实体对象持久化到数据库中  
JPA提供的技术：

1）ORM映射元数据：JPA支持XML和JDK 5.0注解两种元数据的形式，元数据描述对象和表之间的映射关系，框架据此将实体对象持久化到数据库表中；

2）JPA 的API：用来操作实体对象，执行CRUD操作，框架在后台替我们完成所有的事情，开发者从繁琐的JDBC和SQL代码中解脱出来。

3）查询语言：通过面向对象而非面向数据库的查询语言查询数据，避免程序的SQL语句紧密耦合。

# jpa 和hibernate的关系 #

JPA是规范，Hibernate是框架，JPA是持久化规范，而Hibernate实现了JPA。

# 在springboot中的 jpa的使用 #

\#\#实体对象  
实体关系映射(ORM)

<table> 
 <thead> 
  <tr> 
   <th>对象端</th> 
   <th>数据库端</th> 
   <th>annotion</th> 
   <th></th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>Class</td> 
   <td>Table</td> 
   <td>@Entity @Table(name=“tablename”)</td> 
   <td></td> 
  </tr> 
  <tr> 
   <td>property</td> 
   <td>column</td> 
   <td>@Column(name = “columnname”)</td> 
   <td></td> 
  </tr> 
  <tr> 
   <td>property</td> 
   <td>primary key</td> 
   <td>@Id @GeneratedValue 详见ID生成策略</td> 
   <td></td> 
  </tr> 
 </tbody> 
</table>

@Table(name="t_dept")
    @Entity
    public class Dept { 
    	@Id
    	@GeneratedValue
    	int did;
    	String dname;

## 映射关系 ##

JPA定义了  
one-to-one、one-to-many、many-to-one、many-to-many 4种关系。

### JPA提供的接口 ###

JpaRepository,最顶层的接口，是一个空的接口，目的是为了统一所有Repository的类型  
CrudRepository ：是Repository的子接口，提供CRUD的功能  
PagingAndSortingRepository：是CrudRepository的子接口，添加分页和排序的功能  
接口举例

@Repository
    public interface JpaDao extends JpaRepository<RiCheng, Integer> { 
    	Page<RiCheng> findGoodsListBySnameContaining(String name,Pageable page);
    }

### jap中的默认查询方法 ###

<table> 
 <thead> 
  <tr> 
   <th>Keyword</th> 
   <th>Sample</th> 
   <th>JPQL snippet</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>Keyword</td> 
   <td>Sample</td> 
   <td>JPQL snippet</td> 
  </tr> 
  <tr> 
   <td>And</td> 
   <td>findByLastnameAndFirstname</td> 
   <td>… where x.lastname = ?1 and x.firstname = ?2</td> 
  </tr> 
  <tr> 
   <td></td> 
   <td></td> 
   <td></td> 
  </tr> 
  <tr> 
   <td>Or</td> 
   <td>findByLastnameOrFirstname</td> 
   <td>… where x.lastname = ?1 or x.firstname = ?2</td> 
  </tr> 
  <tr> 
   <td>Is,Equals</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 ⇐ ?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(parameter bound with appended %)</td> 
  </tr> 
  <tr> 
   <td>EndingWith</td> 
   <td>findByFirstnameEndingWith</td> 
   <td>… where x.firstname like ?1(parameter bound with prepended %)</td> 
  </tr> 
  <tr> 
   <td>Containing1</td> 
   <td>findByFirstnameContaining</td> 
   <td>… where x.firstname like ?1(parameter bound wrapped in%)</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 ages)</td> 
   <td>… where x.age in ?1</td> 
  </tr> 
  <tr> 
   <td>NotIn</td> 
   <td>findByAgeNotIn(Collection age)</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.firstame) = UPPER(?1)</td> 
  </tr> 
 </tbody> 
</table>

### jpa的分页 ###

设置分页  
PageRequest pageRequest = PageRequest.of(1, 3);

传参：Page findGoodsListBySnameContaining(String name,Pageable page);