springboot 整合jpa一

jpa 概述

全稱Java Persistence API，通過JDK 5.0註解或XML描述對象－關係表的映射關係，並將運行期的實體對象持久化到數據庫中
JPA提供的技術：

1）ORM映射元數據：JPA支持XML和JDK 5.0註解兩種元數據的形式，元數據描述對象和表之間的映射關係，框架據此將實體對象持久化到數據庫表中；

2）JPA 的API：用來操作實體對象，執行CRUD操作，框架在後臺替我們完成所有的事情，開發者從繁瑣的JDBC和SQL代碼中解脫出來。

3）查詢語言：通過面向對象而非面向數據庫的查詢語言查詢數據，避免程序的SQL語句緊密耦合。

jpa 和hibernate的關係

JPA是規範，Hibernate是框架，JPA是持久化規範，而Hibernate實現了JPA。

在springboot中的 jpa的使用

##實體對象
實體關係映射(ORM)

對象端	數據庫端	annotion
Class	Table	@Entity @Table(name=“tablename”)
property	column	@Column(name = “columnname”)
property	primary key	@Id @GeneratedValue 詳見ID生成策略

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

映射關係

JPA定義了
one-to-one、one-to-many、many-to-one、many-to-many 4種關係。

JPA提供的接口

JpaRepository,最頂層的接口，是一個空的接口，目的是爲了統一所有Repository的類型
CrudRepository ：是Repository的子接口，提供CRUD的功能
PagingAndSortingRepository：是CrudRepository的子接口，添加分頁和排序的功能
接口舉例

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

jap中的默認查詢方法

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的分頁

設置分頁
PageRequest pageRequest = PageRequest.of(1, 3);

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