Play Framework / Scala:抽象存储库和 Json de/serialization
Play Framework / Scala: abstract repository and Json de/serialization
这个问题可能更多地是关于 Scala 而不是 Play,但它是:我正在尝试为常见的数据库操作实现存储库的抽象。
trait Entity {
def id: UUID
}
trait Repository[T <: Entity] {
val JSON_KEY_ID = "_id"
def collection: JSONCollection
def insert(t: T): Future[Either[String, T]] = {
collection.insert(t).map(wr => if (wr.ok) Right(t) else Left(wr.getMessage()))
.recover { case t => Left(t.getMessage) }
}
def update(t: T): Future[Either[String, T]] = {
val selector = Json.obj(JSON_KEY_ID -> t.id.toString)
collection.update(selector, t).map(wr => if (wr.ok) Right(t) else Left(wr.getMessage()))
.recover { case t => Left(t.getMessage) }
}
}
然后我有了我想使用的对象:
case class UserDAO(id: UUID) extends Entity[UserDAO]
object UserDAO {
val JSON_KEY_ID = "_id"
implicit val userDaoWrites: OWrites[UserDAO] = new OWrites[UserDAO] {
def writes(user: UserDAO): JsObject = Json.obj(
JSON_KEY_ID -> JsString(user.id.toString)
)
}
implicit val userDaoReads: Reads[UserDAO] = (
(__ \ JSON_KEY_ID).read[UUID]
)(UserDAO.apply _)
}
然后我这样定义它的存储库:
class UserRepository @Inject()(val reactiveMongoApi: ReactiveMongoApi) extends Repository[UserDAO] {
val db = reactiveMongoApi.db
override def collection: JSONCollection = db.collection[JSONCollection]("users")
}
我得到的错误是
No Json serializer as JsObject found for type T. Try to implement an implicit OWrites or OFormat for this type.
collection.insert(t).map(wr => if (wr.ok) Right(t) else Left(wr.getMessage()))
^
我试过提供implicit OWrites[T]
,甚至implicit OWrites[_]
都无济于事。也许我想要实现的目标是不可能的。如果没有,我该如何解决?非常感谢。
您应该可以只使用上下文绑定。
trait Entity {
def id: UUID
}
class Repository[T <: Entity : Writes] {
...
}
这将确保如果范围内存在隐式 Writes[T]
,它将可用于您的插入和更新功能。
这个问题可能更多地是关于 Scala 而不是 Play,但它是:我正在尝试为常见的数据库操作实现存储库的抽象。
trait Entity {
def id: UUID
}
trait Repository[T <: Entity] {
val JSON_KEY_ID = "_id"
def collection: JSONCollection
def insert(t: T): Future[Either[String, T]] = {
collection.insert(t).map(wr => if (wr.ok) Right(t) else Left(wr.getMessage()))
.recover { case t => Left(t.getMessage) }
}
def update(t: T): Future[Either[String, T]] = {
val selector = Json.obj(JSON_KEY_ID -> t.id.toString)
collection.update(selector, t).map(wr => if (wr.ok) Right(t) else Left(wr.getMessage()))
.recover { case t => Left(t.getMessage) }
}
}
然后我有了我想使用的对象:
case class UserDAO(id: UUID) extends Entity[UserDAO]
object UserDAO {
val JSON_KEY_ID = "_id"
implicit val userDaoWrites: OWrites[UserDAO] = new OWrites[UserDAO] {
def writes(user: UserDAO): JsObject = Json.obj(
JSON_KEY_ID -> JsString(user.id.toString)
)
}
implicit val userDaoReads: Reads[UserDAO] = (
(__ \ JSON_KEY_ID).read[UUID]
)(UserDAO.apply _)
}
然后我这样定义它的存储库:
class UserRepository @Inject()(val reactiveMongoApi: ReactiveMongoApi) extends Repository[UserDAO] {
val db = reactiveMongoApi.db
override def collection: JSONCollection = db.collection[JSONCollection]("users")
}
我得到的错误是
No Json serializer as JsObject found for type T. Try to implement an implicit OWrites or OFormat for this type.
collection.insert(t).map(wr => if (wr.ok) Right(t) else Left(wr.getMessage()))
^
我试过提供implicit OWrites[T]
,甚至implicit OWrites[_]
都无济于事。也许我想要实现的目标是不可能的。如果没有,我该如何解决?非常感谢。
您应该可以只使用上下文绑定。
trait Entity {
def id: UUID
}
class Repository[T <: Entity : Writes] {
...
}
这将确保如果范围内存在隐式 Writes[T]
,它将可用于您的插入和更新功能。