Spring Boot -- Spring Data Jpa(2)

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方法名中支持的关键字

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 findByStartDateBetween … where x.startDate between ?1 and ?2 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 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 %) Containing 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)

属性表达式

在进行方法名解析时,会先将方法名多余的前缀移除,比如find,findBy,read,readBy,get,getBy,然后对剩下的部分进行解析.
findByAddressZipCode(),框架在解析方法时,先剔除findBy,然后对AddressZipCode进行解析.
1). Jpa会先判断在判断实体类中是否存在addressZipCode属性.如果存在,则进行where x.addressZipCode = ?1查询.
2). 若不存在,则从右边开始将字符串按”驼峰”命名的规则将其分为两部分,然后企图查找对应的属性.即一开始分为addressZip和code,然后查找实体类中是否存在addressZip对象属性,且addressZip类中是否存在code属性.若存在,则进行where x.addressZip.zone = ?1查询.
3). 若addressZip与code不存在,则继续拆分为address与zipCode,查找实体类中是否存在address对象属性以及address对象中是否存在zipCode.若存在,进行where x.address.zipCode查询.
4). 若address存在,zipCode不存在,则继续拆分,address中是否存在zip,zip中是否存在code,以where x.address.zip.code = ?1查询.
5). 若都不存在,则在编译时将报错.
6). 可以使用findByAddress_ZipCode进行定义解析方式.即x.address.zipCode
7). 如果实体类的属性过于复杂,不建议使用方法名衍生查询的方法.

Result Query

去重复

List<Employee> findDistinctByFirstname(String name);

可以使用findDistinctBy对查询结果去重复.将生成查询语句

select distinct ... from Entity x where x.firstname=?1

限制个数

User findFirstByOrderByLastnameAsc()User findTopByOrderByAgeDesc();List<User> findFirst10ByLastname(String lastname);List<User> findTop10ByLastname(String lastname);

可以使用First或Top来限制返回的结果数,如果First与Top后面没跟数字,则默认为1

分页

Page<Employee> findAll(Page page);

在参数中加入Pageable对象,即可对返回值自动进行分页,返回值将更改为Page<>

排序

List<Employee> findAll(Sort sort);Page<Employee> findAll(Page page,Sort sort);

在参数中加入Sort对象,即可对返回值进行排序

Count Query

Long countByAgeBetween(int age1,int age2);

以countBy开头的方法名,可以解析为计算个数语句.随后的属性表达式同findBy

Delete Query

Long deleteByFirstName(String firstName);

以deleteBy开头或removeBy的方法名,可以解析为删除语句.随后的属性表达式同findBy

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