JPA-JpaRepository方法命名语法说明

前言

梳理了一遍JPA的方法命名语法,记录一下,以便后续备查。

注:本文不介绍JPL语法,版本为spring-data-jpa-2.3.0.RELEASE。

假设实体类名为 aaa,且定义如下:

import lombok.Data;
import javax.persistence.Entity;
import javax.persistence.Id;
@Entity
@Data
public class aaa {
    @Id
    private long id;
    private long restId;
    private int dishHour;
    private int num;
}

对应的仓储层接口定义:

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;
import javax.transaction.Transactional;
import java.util.List;
@Repository
public interface aaaRepository extends JpaRepository {
    int countByDishHourAndRestId(int hour, long restId);
    boolean existsByDishHourAndRestId(int hour, long restId);
    List findByDishHourAndRestId(int hour, long restId);
    aaa findTopByDishHourAndRestId(int hour, long restId);
    @Transactional
    int deleteByDishHourAndRestId(int hour, long restId);
}

JPA的语法分为如下5种:

1、count相关,返回值为int 或 long

int countByDishHourAndRestId(int hour, long restId);
int countaaaByDishHourAndRestId(int hour, long restId);
int countaaasByDishHourAndRestId(int hour, long restId);
int countAllByDishHourAndRestId(int hour, long restId);

上面这4个方法是一样的,对应的SQL如下:

select count(id) from aaa where dishHour=? and restId=?

下面这种定义,没有意义,知晓一下就好:

int countDistinctByDishHourAndRestId(int hour, long restId);

对应SQL如下,如果表中有主键,功能跟countBy是一致的,浪费性能:

select distinct count(distinct id) from aaa where dishHour=? and restId=?

2、exists相关,返回值只能是 boolean

boolean existsByDishHourAndRestId(int hour, long restId);
boolean existsaaaByDishHourAndRestId(int hour, long restId);
boolean existsaaasByDishHourAndRestId(int hour, long restId);
boolean existsAllByDishHourAndRestId(int hour, long restId);

上面这4个方法是一样的,对应的SQL如下:

select id from aaa where dishHour=? and restId=? limit 1

下面这种定义,没有意义,知晓一下就好:

boolean existsDistinctByDishHourAndRestId(int hour, long restId);

对应SQL如下,功能跟existsBy是一致的,多余:

select distinct id from aaa where dishHour=? and restId=? limit 1

3、find相关,返回值是数组List

List findByDishHourAndRestId(int hour, long restId);
List findaaaByDishHourAndRestId(int hour, long restId);
List findaaasByDishHourAndRestId(int hour, long restId);
List findAllByDishHourAndRestId(int hour, long restId);
List getByDishHourAndRestId(int hour, long restId);
List getaaaByDishHourAndRestId(int hour, long restId);
List getaaasByDishHourAndRestId(int hour, long restId);
List getAllByDishHourAndRestId(int hour, long restId);
List queryByDishHourAndRestId(int hour, long restId);
List queryaaaByDishHourAndRestId(int hour, long restId);
List queryaaasByDishHourAndRestId(int hour, long restId);
List queryAllByDishHourAndRestId(int hour, long restId);
List readByDishHourAndRestId(int hour, long restId);
List readaaaByDishHourAndRestId(int hour, long restId);
List readaaasByDishHourAndRestId(int hour, long restId);
List readAllByDishHourAndRestId(int hour, long restId);
List streamByDishHourAndRestId(int hour, long restId);
List streamaaaByDishHourAndRestId(int hour, long restId);
List streamaaasByDishHourAndRestId(int hour, long restId);
List streamAllByDishHourAndRestId(int hour, long restId);

上面这20个方法是一样的,对应的SQL如下:

select id,dishHour,num,restId from aaa where dishHour=? and restId=?

下面这种定义,没有意义,知晓一下就好:

List findDistinctByDishHourAndRestId(int hour, long restId);

对应SQL如下,如果表中有主键,功能跟findBy是一致的,多余:

select distinct id,dishHour,num,restId from aaa where dishHour=? and restId=?

4、findFirst相关,返回值是aaa

aaa findFirstByDishHourAndRestId(int hour, long restId);
aaa findTopByDishHourAndRestId(int a, long b);
aaa getFirstByDishHourAndRestId(int hour, long restId);
aaa getTopByDishHourAndRestId(int a, long b);
aaa queryFirstByDishHourAndRestId(int hour, long restId);
aaa queryTopByDishHourAndRestId(int a, long b);
aaa readFirstByDishHourAndRestId(int hour, long restId);
aaa readTopByDishHourAndRestId(int a, long b);
aaa streamFirstByDishHourAndRestId(int hour, long restId);
aaa streamTopByDishHourAndRestId(int a, long b);

上面这10个方法是一样的,对应的SQL如下:

select id,dishHour,num,restId from aaa where dishHour=? and restId=? limit 1

注:返回值也可以改成List,但是SQL不变,返回的数组也只有一条数据

下面这种定义,没有意义,知晓一下就好:

List findDistinctFirstByDishHourAndRestId(int hour, long restId);

对应SQL如下,如果表中有主键,功能跟countBy是一致的,多余:

select distinct id,dishHour,num,restId from aaa where dishHour=? and restId=? limit 1

5、delete相关,返回值是int,删除行数

@Transactional
int deleteaaaByDishHourAndRestId(int a, long b);
@Transactional
int deleteaaasByDishHourAndRestId(int a, long b);
@Transactional
int deleteAllByDishHourAndRestId(int a, long b);
@Transactional
int deleteByDishHourAndRestId(int a, long b);
@Transactional
int removeaaaByDishHourAndRestId(int a, long b);
@Transactional
int removeaaasByDishHourAndRestId(int a, long b);
@Transactional
int removeAllByDishHourAndRestId(int a, long b);
@Transactional
int removeByDishHourAndRestId(int a, long b);

上面这8个方法是一样的,对应有2条SQL,如下:

select id,dishHour,num,restId from aaa where dishHour=? and restId=?
delete from aaa where id=?

注:先SELECT查找主键,再进行删除,所以必须在方法前加注解Transactional,提供事务,否则会抛异常。

下面这种定义,没有意义,知晓一下就好:

int deleteDistinctByDishHourAndRestId(int hour, long restId);

对应SQL如下,如果表中有主键,功能跟deleteBy是一致的,多余:

select distinct id,dishHour,num,restId from aaa where dishHour=? and restId=?

注1:方法By后面的语法,可以参考下图,或官方文档

JPA-JpaRepository方法命名语法说明_第1张图片

注2:JPA Query注解问题:

SQL里可以用 #{#entityName} 占位符,替代手写表名,如:

@Query(value = "select * from #{#entityName} where 1=2", nativeQuery = true)
aaa selectXXX();

INSERT、UPDATE、DELETE这3种DML操作,返回值只能是void、int、long,且必须增加2个注解,例如:

// 返回值不是void、int、long,报错:
// Modifying queries can only use void or int/Integer as return type!
// 不加 Transactional 报错: 
// javax.persistence.TransactionRequiredException: Executing an update/delete query
@Transactional
// 不加Modifing 报错:
// Can not issue data manipulation statements with executeQuery().
@Modifying
@Query(value = "update #{#entityName} set num=num+1 where id=6", nativeQuery = true)
int doupdate();

注3:JPA原生方法列表:

List findAll();
List findAll(Sort var1);
List findAllById(Iterable var1);
 List saveAll(Iterable var1);
void flush();
 S saveAndFlush(S var1);
void deleteInBatch(Iterable var1);
void deleteAllInBatch();
T getOne(ID var1);
 List findAll(Example var1);
 List findAll(Example var1, Sort var2);

以上为个人经验,希望能给大家一个参考,也希望大家多多支持脚本之家。