springboot 整合jpa一

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)

对象端	数据库端	annotion
Class	Table	@Entity @Table(name=“tablename”)
property	column	@Column(name = “columnname”)
property	primary key	@Id @GeneratedValue 详见ID生成策略

@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

Keyword	Sample	JPQL snippet
Keyword	Sample	JPQL snippet
And	findByLastnameAndFirstname	… where x.lastname = ?1 and x.firstname = ?2
Or	findByLastnameOrFirstname	… where x.lastname = ?1 or x.firstname = ?2
Is,Equals	findByFirstname,findByFirstnameIs,findByFirstnameEquals	… where x.firstname = ?1
Between	findByStartDateBetween	… where x.startDate between ?1 and ?2
LessThan	findByAgeLessThan	… where x.age < ?1
LessThanEqual	findByAgeLessThanEqual	… where x.age ⇐ ?1
GreaterThan	findByAgeGreaterThan	… where x.age > ?1
GreaterThanEqual	findByAgeGreaterThanEqual	… where x.age >= ?1
After	findByStartDateAfter	… where x.startDate > ?1
Before	findByStartDateBefore	… where x.startDate < ?1
IsNull	findByAgeIsNull	… where x.age is null
IsNotNull,NotNull	findByAge(Is)NotNull	… where x.age not null
Like	findByFirstnameLike	… where x.firstname like ?1
NotLike	findByFirstnameNotLike	… where x.firstname not like ?1
StartingWith	findByFirstnameStartingWith	… where x.firstname like ?1(parameter bound with appended %)
EndingWith	findByFirstnameEndingWith	… where x.firstname like ?1(parameter bound with prepended %)
Containing1	findByFirstnameContaining	… where x.firstname like ?1(parameter bound wrapped in%)
OrderBy	findByAgeOrderByLastnameDesc	… where x.age = ?1 order by x.lastname desc
Not	findByLastnameNot	… where x.lastname <> ?1
In	findByAgeIn(Collection ages)	… where x.age in ?1
NotIn	findByAgeNotIn(Collection age)	… where x.age not in ?1
TRUE	findByActiveTrue()	… where x.active = true
FALSE	findByActiveFalse()	… where x.active = false
IgnoreCase	findByFirstnameIgnoreCase	… where UPPER(x.firstame) = UPPER(?1)

jpa的分页

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

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