如果没有正确的错误说明，Slick会抛出Null Pointer Exception

Question

我一直在为我的游戏项目使用Slick 2 for DB mgmt，但是下面的方法是抛出Null Pointer Exception而我实际上无法找出抛出异常的原因。

其他与数据库相关的功能正常工作，就像我可以使用evolution插件创建表格一样。

val userProjection: TableQuery[UserProjection] = TableQuery[UserProjection]

def fetch(identity: IdentityId): Option[Users] = {
        val user = identity.userId
//user is not null
        val query = userProjection.filter(_.userId === user)// Exception thrown in this line
        //val query = userProjection.filter(value => value.userId === identity.userId && value.providerId === identity.providerId)
        val result = SQLDB.withSession { implicit session =>
          val res = query.list
          if (res.size > 0) {
            res.headOption
          } else {
            None
          }
        }
        if (result != None) {
          Some(convertSingleResultSet(result))
        } else {
          None
        }
      }

投影类

class UserProjection(tag: Tag) extends Table[Users](tag, "identities_47") {

  implicit def string2AuthenticationMethod = MappedColumnType.base[AuthenticationMethod, String](
    authenticationMethod => authenticationMethod.method,
    string => AuthenticationMethod(string))

  implicit def tuple2OAuth1Info(tuple: (Option[String], Option[String])): Option[OAuth1Info] = tuple match {
    case (Some(token), Some(secret)) => Some(OAuth1Info(token, secret))
    case _ => None
  }

  implicit def tuple2OAuth2Info(tuple: (Option[String], Option[String], Option[Int], Option[String])): Option[OAuth2Info] = tuple match {
    case (Some(token), tokenType, expiresIn, refreshToken) => Some(OAuth2Info(token, tokenType, expiresIn, refreshToken))
    case _ => None
  }

  implicit def tuple2PasswordInfo(tuple: (Option[String], Option[String], Option[String])) = tuple match {
    case (Some(hasher), Some(password), salt) =>
      Some(PasswordInfo(hasher, password, salt))
    case _ => None
  }

  implicit def tuple2IdentityId(tuple: (String, String)): IdentityId = tuple match {
    case (userId, providerId) => IdentityId(userId, providerId)
  }

  //def uid = column[Long]("id", O.PrimaryKey, O.AutoInc)
  def userId = column[String]("userId")
  def providerId = column[String]("providerId")
  def email = column[Option[String]]("email")
  def firstName = column[String]("firstName")
  def lastName = column[String]("lastName")
  def fullName = column[String]("fullName")
  def authMethod = column[AuthenticationMethod]("authMethod")
  def avatarUrl = column[Option[String]]("avatarUrl")
  // oAuth 1
  def token = column[Option[String]]("token")
  def secret = column[Option[String]]("secret")
  // oAuth 2
  def accessToken = column[Option[String]]("accessToken")
  def tokenType = column[Option[String]]("tokenType")
  def expiresIn = column[Option[Int]]("expiresIn")
  def refreshToken = column[Option[String]]("refreshToken")
  //PasswordInfo
  def hasher = column[Option[String]]("hasher")
  def password = column[Option[String]]("password")
  def salt = column[Option[String]]("salt")

  def * : ProvenShape[Users] = {
    val shapedValue = (
      userId,
      providerId,
      firstName,
      lastName,
      fullName,
      email,
      avatarUrl,
      authMethod,
      token,
      secret,
      accessToken,
      tokenType,
      expiresIn,
      refreshToken,
      hasher,
      password,
      salt).shaped
    shapedValue.<>({
      tuple =>
        Users.apply(
          identityId = tuple2IdentityId(tuple._1, tuple._2),
          firstName = tuple._3,
          lastName = tuple._4,
          fullName = tuple._5,
          email = tuple._6,
          avatarUrl = tuple._7,
          authMethod = tuple._8,
          oAuth1Info = (tuple._9, tuple._10),
          oAuth2Info = (tuple._11, tuple._12, tuple._13, tuple._14),
          passwordInfo = (tuple._15, tuple._16, tuple._17))
    }, {
      (u: Users) =>
        Some {
          (u.identityId.userId,
            u.identityId.providerId,
            u.firstName,
            u.lastName,
            u.fullName,
            u.email,
            u.avatarUrl,
            u.authMethod,
            u.oAuth1Info.map(_.token),
            u.oAuth1Info.map(_.secret),
            u.oAuth2Info.map(_.accessToken),
            u.oAuth2Info.flatMap(_.tokenType),
            u.oAuth2Info.flatMap(_.expiresIn),
            u.oAuth2Info.flatMap(_.refreshToken),
            u.passwordInfo.map(_.hasher),
            u.passwordInfo.map(_.password),
            u.passwordInfo.flatMap(_.salt))
        }
    })
  }
}

和堆栈跟踪，

play.api.Application$$anon$1: Execution exception[[NullPointerException: null]]
    at play.api.Application$class.handleError(Application.scala:293) ~[play_2.10-2.2.3.jar:2.2.3]
    at play.api.DefaultApplication.handleError(Application.scala:399) [play_2.10-2.2.3.jar:2.2.3]
    at play.core.server.netty.PlayDefaultUpstreamHandler$$anonfun$13$$anonfun$apply$1.applyOrElse(PlayDefaultUpstreamHandler.scala:166) [play_2.10-2.2.3.jar:2.2.3]
    at play.core.server.netty.PlayDefaultUpstreamHandler$$anonfun$13$$anonfun$apply$1.applyOrElse(PlayDefaultUpstreamHandler.scala:163) [play_2.10-2.2.3.jar:2.2.3]
    at scala.runtime.AbstractPartialFunction.apply(AbstractPartialFunction.scala:33) [scala-library-2.10.4.jar:na]
    at scala.util.Failure$$anonfun$recover$1.apply(Try.scala:185) [scala-library-2.10.4.jar:na]
Caused by: java.lang.NullPointerException: null
    at models.dao.UsersDao$.fetch(UsersDao.scala:153) ~[classes/:na]
    at controllers.Facebooks$$anonfun$authorize$1.apply(Facebooks.scala:121) ~[classes/:na]
    at controllers.Facebooks$$anonfun$authorize$1.apply(Facebooks.scala:112) ~[classes/:na]
    at play.api.mvc.ActionBuilder$$anonfun$apply$10.apply(Action.scala:221) ~[play_2.10-2.2.3.jar:2.2.3]
    at play.api.mvc.ActionBuilder$$anonfun$apply$10.apply(Action.scala:220) ~[play_2.10-2.2.3.jar:2.2.3]
    at play.api.mvc.Action$.invokeBlock(Action.scala:357) ~[play_2.10-2.2.3.jar:2.2.3]