Question

我可以将case类映射到光滑的数据库表： -

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)
}

case类具有默认情况下通过slick转换为数据库类型的字段，所以一切都很好。

但是，如果我的case类中的字段不是默认数据库类型，则这不起作用。 Slick允许我使用MappedColumnType提供与有效数据库类型的隐式转换，所以我尝试了这一点，请注意我现在使用的是Java LocalDatetime而不是sql Timestamp。

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 }
  )
}

我添加了隐式映射列，我仍然在投影和隐式解析中得到编译错误编译错误是： -

[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")

如果我修改了def时间并添加了类型归属，我会得到一个不同的错误，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 }
  )
}

给出了这个错误： -

[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

如果案例类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类映射到表？

欢呼声

Answer 1

经过几天的挣扎，我找到了答案： - /

问题是在Table类之后声明了隐式MappedColumnType。由于某种原因，即使我将其导入表格之上，这也会破坏隐式解决方案。

当我删除案例类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表定义之上，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。感谢。

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类映射到Slick中的表？

1 个答案: