Question

我正在使用anorm访问我的数据库上的数据。 DB使用另一个用Java编写的服务编写，并使用ebean保存。

我有以下scala对象

import java.sql.Connection

import scala.concurrent.{ Future, blocking, future }
import scala.concurrent.ExecutionContext.Implicits.global

import anorm.{ SQL, SqlQuery, SqlRow, sqlToSimple, toParameterValue }
import play.api.Logger
import play.api.Play.current
import play.api.db.DB

object Queries {

  private val readDataSource: String = play.Configuration.root().getString("data.provider.api.source", "default")
  //better IO execution context

  import play.api.libs.concurrent.Execution.Implicits.defaultContext

  private val dataSetDescription: SqlQuery = SQL("SELECT DISTINCT platform, name FROM data_nugget")

  private val identityCreationTime: SqlQuery = SQL("SELECT i.creation_time FROM identity i WHERE platform = {pfm} AND userid = {uid};")

  private val identityData: SqlQuery = SQL("SELECT n.name, n.value FROM data_nugget n WHERE platform = {pfm} AND userid = {uid};")

  private val playerData: SqlQuery = SQL("SELECT n.platform, n.name, n.value, r.userid, r.registration_time FROM data_nugget n JOIN registration r ON n.platform=r.platform AND n.userid=r.userid  WHERE r.playerid = {pid} AND r.application = {app};")

  private def withAsyncAnormConnection(function: Connection => Stream[SqlRow]): Future[List[SqlRow]] = {
    future {
      blocking {
        DB.withConnection(readDataSource)(c => function(c)).toList
      }
    }
  }

  def fetchDistinctDataNames(): Future[List[SqlRow]] = {
    withAsyncAnormConnection(implicit c => dataSetDescription())
  }

  def fetchIdentityCreationTime(platform: String, userid: String): Future[List[SqlRow]] = {
    withAsyncAnormConnection(implicit c => identityCreationTime.on("pfm" -> platform, "uid" -> userid)())
  }

  def fetchIdentityData(platform: String, userid: String): Future[List[SqlRow]] = {
    withAsyncAnormConnection(implicit c => identityData.on("pfm" -> platform, "uid" -> userid)())
  }

  def fetchRegistrationData(game: String, playerid: String): Future[List[SqlRow]] = {
    withAsyncAnormConnection(implicit c => playerData.on("app" -> game, "pid" -> playerid)())
  }

}

我用它来封装期货中的SQL查询执行。

每当我运行任何这些查询时，我都会在以下堆栈跟踪中获得错误：

(Error,com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1073)
com.mysql.jdbc.SQLError.createSQLException(SQLError.java:987)
com.mysql.jdbc.SQLError.createSQLException(SQLError.java:982)
com.mysql.jdbc.SQLError.createSQLException(SQLError.java:927)
com.mysql.jdbc.ResultSetImpl.checkClosed(ResultSetImpl.java:794)
com.mysql.jdbc.ResultSetImpl.next(ResultSetImpl.java:7139)
anorm.Sql$$anonfun$resultSetToStream$1.apply(Anorm.scala:527)
anorm.Sql$$anonfun$resultSetToStream$1.apply(Anorm.scala:527)
anorm.Useful$.unfold(Anorm.scala:315)
anorm.Useful$$anonfun$unfold$1.apply(Anorm.scala:317)
anorm.Useful$$anonfun$unfold$1.apply(Anorm.scala:317)
scala.collection.immutable.Stream$Cons.tail(Stream.scala:1078)
scala.collection.immutable.Stream$Cons.tail(Stream.scala:1070)
scala.collection.immutable.Stream.foreach(Stream.scala:548)
scala.collection.generic.Growable$class.$plus$plus$eq(Growable.scala:48)
scala.collection.mutable.ListBuffer.$plus$plus$eq(ListBuffer.scala:178)
scala.collection.mutable.ListBuffer.$plus$plus$eq(ListBuffer.scala:45)
scala.collection.TraversableLike$class.to(TraversableLike.scala:629)
scala.collection.AbstractTraversable.to(Traversable.scala:105)
scala.collection.TraversableOnce$class.toList(TraversableOnce.scala:243)
scala.collection.AbstractTraversable.toList(Traversable.scala:105)
controllers.dataprovider.data.Queries$$anonfun$withAsyncAnormConnection$1$$anonfun$apply$1.apply(Queries.scala:31)
controllers.dataprovider.data.Queries$$anonfun$withAsyncAnormConnection$1$$anonfun$apply$1.apply(Queries.scala:31)
scala.concurrent.impl.ExecutionContextImpl$DefaultThreadFactory$$anon$2$$anon$3.block(ExecutionContextImpl.scala:44)
scala.concurrent.forkjoin.ForkJoinPool.managedBlock(ForkJoinPool.java:2803)
scala.concurrent.impl.ExecutionContextImpl$DefaultThreadFactory$$anon$2.blockOn(ExecutionContextImpl.scala:41)
scala.concurrent.package$.blocking(package.scala:50)
controllers.dataprovider.data.Queries$$anonfun$withAsyncAnormConnection$1.apply(Queries.scala:30)
controllers.dataprovider.data.Queries$$anonfun$withAsyncAnormConnection$1.apply(Queries.scala:30)
scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1(Future.scala:24)
scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:24)
scala.concurrent.forkjoin.ForkJoinTask$AdaptedRunnableAction.exec(ForkJoinTask.java:1417)
scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:262)
scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:975)
scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1478)
scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:104))

我已经在使用jdbc的先前Java服务上遇到了那些，但是在这里我没有触及ResultSet，我甚至从连接中收到的行的流返回asap列表。

发生了什么事？我在哪里关闭ResultSet？我重构的是什么错误？

作为一个注释，在这个服务的原型上（当所有东西都在控制器中时）我曾经在代码中直接使用SQL（“...”）：

future {
    blocking {
      DB.withConnection(implicit c => {
        SQL("SELECT DISTINCT platform, name FROM data_nugget")().map(row => (row[String]("platform"), row[String]("name"))).toArray
      })
    }
  }

它运作得很好。

PS：很抱歉堆栈跟踪和代码的长拷贝/粘贴......试图详细说明。

Answer 1

我自己解决了这个问题，这是一个非常好的路线。

我改变了这个功能

  private def withAsyncAnormConnection(function: Connection => Stream[SqlRow]): Future[List[SqlRow]] = {
    future {
      blocking {
        DB.withConnection(readDataSource)(c => function(c)).toList
      }
    }
  }

到这个：

  private def withAsyncAnormConnection(function: Connection => Stream[SqlRow]): Future[List[SqlRow]] = {
    future {
      blocking {
        DB.withConnection(readDataSource)(c => function(c).toList)
      }
    }
  }

诀窍在于我使用的是withConnection的“贷款模式”，所以在发布连接之前，我需要通过Stream来获取所有行。
该连接仅在此圆括号(c => function(c).toList)

内有效

Answer 2

适用于您的代码与无法运行的代码之间存在差异。在您的工作示例中，您在map个Stream个实例上调用Row。在非工作示例中，您在不使用toList的情况下调用map。也许map强制对ResultSet块中的基础withConnection进行全面处理而toList不是，在您离开withConnection之前将其保持为懒惰阻止基础ResultSet关闭的块。也许你可以修改你的新代码来尝试映射结果（将Row映射到它自己，没有实际的映射逻辑），看看这是否修复了什么。

我在哪里迭代我的ResultSet一次太多了？或者为什么关闭？

2 个答案: