映射列类型 Slick 3.1.1

我是 Slick 的新手，很难将 java.sql.date/time/timestamp 映射到 jodatime。

trait ColumnTypeMappings {

  val profile: JdbcProfile
  import profile.api._

  val localTimeFormatter = DateTimeFormat.forPattern("HH:mm:ss")
  val javaTimeFormatter = new SimpleDateFormat("HH:mm:ss")

  implicit val myDateColumnType = MappedColumnType.base[LocalDate, Date](
    ld => new        java.sql.Date(ld.toDateTimeAtStartOfDay(DateTimeZone.UTC).getMillis),
    d  => new LocalDateTime(d.getTime).toLocalDate
  )

  implicit val myTimeColumnType = MappedColumnType.base[LocalTime, Time](
    lt => new java.sql.Time(javaTimeFormatter.parse(lt.toString(localTimeFormatter)).getTime),
    t  => new LocalTime(t.getTime)
  )

  implicit val myTimestampColumnType = MappedColumnType.base[DateTime, Timestamp](
    dt => new java.sql.Timestamp(dt.getMillis),
    ts => new DateTime(ts.getTime, DateTimeZone.UTC)
  )

}

在自动生成的 Tables.scala 中，我包含如下映射：

trait Tables extends ColumnTypeMappings {
  val profile: slick.driver.JdbcDriver
  import profile.api._
  import scala.language.implicitConversions
  // + rest of the auto generated code by slick codegen
}

总结一下，我这样使用：

object TestTables extends Tables {
  val profile = slick.driver.MySQLDriver
}

import Tables._
import profile.api._

val db = Database.forURL("url", "user", "password", driver = "com.mysql.jdbc.Driver")
val q = Company.filter(_.companyid === 1).map(._name)
val action = q.result
val future = db.run(action)
val result = Await.result(future, Duration.Inf)

运行此命令时，我在以下位置收到 NullPointerException：隐式 val myDateColumnType...。我已经验证，如果删除映射，最后一块代码可以工作。

尝试改变implicit val to implicit def在你的定义中MappedColumnTypes。原因与给出的答案有关马克西姆·切尔年科 https://stackoverflow.com/users/5812581/maksym-chernenko对此question https://stackoverflow.com/questions/33510259/error-injecting-constructor-when-mapping-enumeration-using-slick-3-1-with-play。一般来说，JdbcProfile驱动程序（定义api.MappedColumnType) 尚未注入，并且：

导致 NPE。您可以制作您的“映射器”val lazy，或者改变它 从val to def（如下所示）

implicit def myDateColumnType = MappedColumnType.base[LocalDate, Date](
  ld => new java.sql.Date(ld.toDateTimeAtStartOfDay(DateTimeZone.UTC).getMillis),
  d  => new LocalDateTime(d.getTime).toLocalDate
)

implicit def myTimeColumnType = MappedColumnType.base[LocalTime, Time](
  lt => new java.sql.Time(javaTimeFormatter.parse(lt.toString(localTimeFormatter)).getTime),
  t  => new LocalTime(t.getTime)
)

implicit def myTimestampColumnType = MappedColumnType.base[DateTime,  Timestamp](
  dt => new java.sql.Timestamp(dt.getMillis),
  ts => new DateTime(ts.getTime, DateTimeZone.UTC)
)