如何将具有非默认字段类型的案例 class 映射到 Slick 中的 table？

Question

我可以将案例 class 映射到灵活的数据库 table:-

case class SomeTimeStamp(id: Option[Long], timestamp: java.sql.Timestamp )

class TimeStampTable(tag: Tag) extends Table[SomeTimeStamp](tag, "TSTAMP_TABLE") {
  def id    = column[Long]("ID", O.AutoInc, O.PrimaryKey)
  def time  = column[java.sql.Timestamp]("TIME")

  def * = (id.?, time) <> (SomeTimeStamp.tupled, SomeTimeStamp.unapply)
}

案例class有slick默认转换为数据库类型的字段，所以一切都很好。

但这不起作用，如果我的字段 class 不是默认数据库类型。 Slick 允许我使用 MappedColumnType 提供与有效数据库类型之间的隐式转换，所以我尝试了这个，请注意我现在使用 Java LocalDatetime 而不是 sql 时间戳。

case class SomeLocalDate(id: Option[Long], timestamp: java.time.LocalDateTime )

class LocalDateTable(tag: Tag) extends Table[SomeLocalDate](tag, "TLDATE_TABLE") {
import LocalDateTable._
  def id    = column[Long]("ID", O.AutoInc, O.PrimaryKey)
  def time  = column[java.time.LocalDateTime]("TIME")

  def * = (id.?, time) <> (SomeLocalDate.tupled, SomeLocalDate.unapply)
}

object LocalDateTable {
  implicit val localDateTimeToTimestamp = MappedColumnType.base[LocalDateTime, Timestamp](
    { Timestamp.valueOf(_) } ,
    { ts => ts.toLocalDateTime }
  )
}

我已经添加和隐式映射列我仍然在投影和隐式解析中遇到编译错误编译错误为：-

[info] Compiling 1 Scala source to ...target/scala-2.11/classes...
[error] db/Tables.scala:92: could not find implicit value for parameter tt: slick.ast.TypedType[java.time.LocalDateTime]
[error]   def time: Rep[LocalDateTime]  = column[java.time.LocalDateTime]("TIME")

如果我修改 def 时间并添加类型归属，我会得到不同的错误，请参见下文。

case class SomeLocalDate(id: Option[Long], timestamp: java.time.LocalDateTime )

class LocalDateTable(tag: Tag) extends Table[SomeLocalDate](tag, "TLDATE_TABLE") {
import LocalDateTable._
  def id    = column[Long]("ID", O.AutoInc, O.PrimaryKey)
  def time: Rep[LocalDateTime]  = column[java.time.LocalDateTime]("TIME")

  def * = (id.?, time) <> (SomeLocalDate.tupled, SomeLocalDate.unapply)
}

object LocalDateTable {
  implicit val localDateTimeToTimestamp = MappedColumnType.base[LocalDateTime, Timestamp](
    { Timestamp.valueOf(_) } ,
    { ts => ts.toLocalDateTime }
  )
}

给出这个错误：-

[info] Compiling 1 Scala source to ...target/scala-2.11/classes...
[error] db/Tables.scala:92: could not find implicit value for parameter tt: slick.ast.TypedType[java.time.LocalDateTime]
[error]   def time: Rep[LocalDateTime]  = column[java.time.LocalDateTime]("TIME")
[error]                                                                  ^
[error]db/Tables.scala:94: No matching Shape found.
[error] Slick does not know how to map the given types.
[error] Possible causes: T in Table[T] does not match your * projection. Or you use an unsupported type in a Query (e.g. scala List).
[error]   Required level: slick.lifted.FlatShapeLevel
[error]      Source type: (slick.lifted.Rep[Option[Long]], slick.lifted.Rep[java.time.LocalDateTime])
[error]    Unpacked type: (Option[Long], java.time.LocalDateTime)
[error]      Packed type: Any
[error]   def * = (id.?, time) <> (SomeLocalDate.tupled, SomeLocalDate.unapply)
[error]                        ^
[error] two errors found

如果案例 class 没有默认支持的数据库类型（例如 LocalDateTime），我需要做什么才能将案例 class 映射到 table？

干杯

Answer 1

经过几天的努力，我找到了答案:-/

问题是在 Table class 之后声明了隐式 MappedColumnType。出于某种原因，即使我将其导入到 table.

上方，这也会打乱隐式分辨率

当我删除大小写 class 并简单地使用元组时，我找到了答案。当我这样做时，出现了以下错误

[info] Compiling 1 Scala source to target/scala-2.11/classes...
[error] /db/Tables.scala:100: could not find implicit value for parameter tt: slick.ast.TypedType[java.time.LocalDateTime]
[error]   def time: Rep[LocalDateTime]  = column[java.time.LocalDateTime]("TIME")
[error]                                                                  ^
[error] /db/Tables.scala:102: type mismatch;
[error]  found   : (slick.lifted.Rep[Option[Long]], slick.driver.H2Driver.api.Rep[java.time.LocalDateTime])
[error]     (which expands to)  (slick.lifted.Rep[Option[Long]], slick.lifted.Rep[java.time.LocalDateTime])
[error]  required: slick.lifted.ProvenShape[(Option[Long], java.time.LocalDateTime)]
[error]  Note: implicit value localDateTimeToTimestamp is not applicable here because it comes after the application point and it lacks an explicit result type
[error]   def * : ProvenShape[(Option[Long], LocalDateTime)] = (id.?, time)
[error]                                                        ^

所以要明确解决方案是将隐式转换放在 table 定义之上（如果在同一个文件中）或将其放在另一个文件中并导入它，请参阅下面的工作解决方案。谢谢

case class SomeLocalDate(id: Option[Long], timestamp: java.time.LocalDateTime )

object LocalDateTableConversions {
  implicit val localDateTimeToTimestamp = MappedColumnType.base[LocalDateTime, Timestamp](
    { Timestamp.valueOf(_) } ,
    { ts => ts.toLocalDateTime }
  )
}
import LocalDateTableConversions._

class LocalDateTable(tag: Tag) extends Table[SomeLocalDate](tag, "TLDATE_TABLE") {
  def id    = column[Long]("ID", O.AutoInc, O.PrimaryKey)
  def time: Rep[LocalDateTime]  = column[java.time.LocalDateTime]("TIME")

  def * = (id.?, time) <> (SomeLocalDate.tupled, SomeLocalDate.unapply)
}

如何将具有非默认字段类型的案例 class 映射到 Slick 中的 table？

How can I map a case class with non-default field types to a table in Slick?

scala

slick