mongodb scala 驱动程序 - 无法检索文档 [英] mongodb scala driver - unable to retrieve a document

问题描述

我无法使用新的 Scala 驱动程序在 mongoDB 中检索文档.

I'm having trouble to retrieve a document in mongoDB using the new scala driver.

这是我的代码:

def retrieveDocument(id: Int,
  collectionName: String, 
  databaseName: String,
  url: String): Option[Document] = {
    var res: Option[Document] = None
    getMongoCollectionImmutable(collectionName, databaseName, url)
      .find(Filters.equal("_id", id))
      .first().subscribe(
      (doc: Document) => res = Some(doc),
      (e: Throwable) => throw e,
      () => ())
    res
  }

def getMongoCollectionImmutable(collectionName: String,databaseName: String, url: String = DEFAULT_URL): MongoCollection[ImmuDoc] = {
  db match {
    case None =>
      getMongoDatabase(databaseName, url).getCollection(collectionName)
    case Some(db) =>
      db.client.getDatabase(databaseName).getCollection(collectionName)
  }

def getMongoDatabase(name: String, url: String = DEFAULT_URL): MongoDatabase = {
  db match {
    case None =>
      db = Some(new _Database(url))
      getMongoDatabase(name)
    case Some(db) =>
      db.client.getDatabase(name)
  }

def retrieve(id: Int): Try[User] = {
  try {
    val docOption = Database.retrieveDocument(id, USER_COLLECTION, DATABASE_NAME, DEFAULT_URL) 
    docOption match {
      case None      => Failure(new Exception(s"Unable to retrieve a user with id ${id}"))
      case Some(doc) => Try(User(doc))
    }
  } catch {
    case e: Throwable => Failure(e)
  }
}

以下是驱动程序的(重要)日志:

Here are the (significant) logs of the driver:

19:16:24.334 DEBUG cluster - Updating cluster description to  {type=STANDALONE, servers=[{address=localhost:27017, type=STANDALONE, roundTripTime=0.7 ms, state=CONNECTED}]
19:16:24.366 INFO  connection - Opened connection [connectionId{localValue:2, serverValue:90}] to localhost:27017
19:16:24.377 DEBUG query - Asynchronously sending query of namespace jobless.user on connection [connectionId{localValue:2, serverValue:90}] to server localhost:27017
19:16:24.381 DEBUG query - Query results received 1 documents with cursor null

这里是我的测试输出

Run starting. Expected test count is: 1
UserTest:
User Document((_id,BsonInt32{value=1}), (firstname,BsonString{value='user1'}), (lastname,BsonString{value='last1'}), (encryptedPass,BsonString{value='pass'}), (cvListPath,BsonArray{values=[{ "name" : "path1", "path" : "name1" }, { "name" : "path2", "path" : "name2" }]}), (motivationLettersPath,BsonArray{values=[{ "name" : "path1", "path" : "name1" }, { "name" : "path2", "path" : "name2" }]}))
-  retrieve from DB Failure(java.lang.Exception: Unable to retrieve a user with id 1) *** FAILED ***
  java.lang.Exception: Unable to retrieve a user with id 1 (UserTest.scala:31)

但是！通过使用wireshark，我可以以正确的方式查看数据库查询并返回文档！(我通过使用 mongo linux 命令进行查询进行了检查，结果完全相同)

But ! By using wireshark I can see the database query the right way and returning the document ! (I checked by doing a query using the mongo linux command and it's the very same)

Frame 1262: 123 bytes on wire (984 bits), 123 bytes captured (984 bits) on interface 0
Linux cooked capture
Internet Protocol Version 4, Src: 127.0.0.1, Dst: 127.0.0.1
Transmission Control Protocol, Src Port: 42714, Dst Port: 27017, Seq: 438, Ack: 1272, Len: 55
Mongo Wire Protocol
    Message Length: 55
    Request ID: 0x00000008 (8)
    Response To: 0x00000000 (0)
    OpCode: Query (2004)
    Query Flags
    fullCollectionName: xxx.user
    Number To Skip: 0
    Number to Return: -1
    Query
        Document length: 14
        Elements
            Element: _id
                Type: Int32 (0x10)
                Value: 1

而且数据库响应也是正确的.

And the database response is also correct.

我做错了什么?

推荐答案

好吧，我责怪自己(以及驱动程序的神秘文档)

Ok so, I blame myself (and the mystic documentation of the driver)

这个驱动是异步的，所以我们只需要等待它完成......所以总结一下(发现 此处) 真正在文档中使用，而不是在驱动程序本身中

This driver is asynchronous, so we just have to wait for it to complete... So to sum up using that (found here) which is genuinely used in the documentation without being in the driver itself

implicit class DocumentObservable[C](val observable: Observable[Document]) extends ImplicitObservable[Document] {
   override val converter: (Document) => String = (doc) => doc.toJson
}

implicit class GenericObservable[C](val observable: Observable[C]) extends ImplicitObservable[C] {
   override val converter: (C) => String = (doc) => doc.toString
}

trait ImplicitObservable[C] {
  val observable: Observable[C]
  val converter: (C) => String

  def results(): Seq[C] = Await.result(observable.toFuture(), Duration(10, TimeUnit.SECONDS))
  def headResult() = Await.result(observable.head(), Duration(10, TimeUnit.SECONDS))
  def printResults(initial: String = ""): Unit = {
    if (initial.length > 0) print(initial)
    results().foreach(res => println(converter(res)))
  }
  def printHeadResult(initial: String = ""): Unit = println(s"${initial}${converter(headResult())}")
}

并改变检索方式:

def retrieveDocument(id: Int, collectionName: String, databaseName: String, url: String): Option[Document] = {
var res: Option[Document] = None
getMongoCollectionImmutable(collectionName, databaseName, url)
  .find(Filters.equal("_id", id))
  .limit(1).results().foreach({ x => res = Some(x) })
res

}

它解决了我的问题.

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