Any-dao-spring provides an any-dao Kotlin extension for spring JPA repositories.
Why? to have typesafe queries which may be composed (similar to JpaSepcificationExecutor) but in pure Kotlin
Define repository:
@Repository
interface UserRepository : KotlinAnyDaoRepository<UserODB, Long>
It extends both JpaSpecificationExecutor<ENTITY> and JpaRepository<ENTITY, KEY>.
Use it like this:
val todos = userRepository.findAllBy(TodoODB::class) {
it.join(UserODB::currentTodo, JoinType.LEFT)
select(it[UserODB::currentTodo])
}
val users = userRepository.findAllBy {
it[UserODB::email] isIn subqueryFrom(TodoODB::class) {
it[TodoODB::importance] greaterThan 10
select(it[TodoODB::name])
}
}
The good practice is to compose complicated query with named specifications that can be copmosed one into another:
// specify extension functions with predicates
fun KRoot<UserODB>.hasAdminOrNormalRole() {
this[UserODB::userRoles].isMember(setOf(UserRole.ADMIN, UserRole.NORMAL))
}
fun KRoot<UserODB>.hasActiveStatus() {
this[UserODB::status] eq UserStatus.ACTIVE
}
fun KRoot<UserODB>.isUserAllowedToCreateTask() {
hasAdminOrNormalRole()
or
hasActiveStatus()
}
...
// later in code:
val users = userRepository.findAllBy {
isUserAllowedToCreateTask()
}