Question

我在mongoDb

中有以下文件

{
    "_id" : 0,
    "GroupUuid" : 0,
    "GroupActivationDate" : "2015-08-01T00:00:00.000+05:00",
    "PurchaseDate" : "2015-08-24T12:42:24.380+05:00",
    "GroupExpirationDate" : "2015-08-28T00:00:00.000+05:00",
    "HousefullDate" : "0001-01-01T01:01:00.000+04:28:12",
    "ArtShare" : {
        "TotalArtShares" : 0,
        "pricePerShare" : 0,
        "ArtworkUuid" : 12,
        "AvailableShares" : 0,
        "SoldShares" : 0
    }
}

当我这样做时db.groupBuying.find({"ArtShare.TotalArtShares":0}).pretty() 上面显示的文件

现在我想使用我正在做的代码

来做到这一点

val cursor=collection.find()
    var obj=new BasicDBObject
     while(cursor.hasNext)
     {
       obj=cursor.next().asInstanceOf[BasicDBObject]

       var id=obj.getString("ArtShare.TotalArtShares").toInt
       log.info("TotalArtShares "+id)
     }
   }

但是抛出异常后

java.lang.NumberFormatException: null
    at java.lang.Integer.parseInt(Integer.java:542)
    at java.lang.Integer.parseInt(Integer.java:615)
    at scala.collection.immutable.StringLike$class.toInt(StringLike.scala:247)
    at scala.collection.immutable.StringOps.toInt(StringOps.scala:30)
    at models.groupbuyingmodels.groupbuyingMongoReadWrite.GroupBuyingStore.write(GroupBuyingStore.scala:43)
    at models.groupbuyingmodels.groupbuyingMongoReadWrite.GroupBuyingWriteMongoActor$$anonfun$receive$1.applyOrElse(GroupBuyingWriteMongoActor.scala:27)
    at akka.actor.Actor$class.aroundReceive(Actor.scala:465)
    at models.groupbuyingmodels.groupbuyingMongoReadWrite.GroupBuyingWriteMongoActor.aroundReceive(GroupBuyingWriteMongoActor.scala:15)
    at akka.actor.ActorCell.receiveMessage(ActorCell.scala:516)
    at akka.actor.ActorCell.invoke(ActorCell.scala:487)
    at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:238)
    at akka.dispatch.Mailbox.run(Mailbox.scala:220)
    at akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec(AbstractDispatcher.scala:393)
    at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
    at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
    at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
    at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)
13:08:55.166 1652348 [ArteciateActorSystem-akka.actor.GroupBuyingWriteMongoActor-dispatcher-6] controller ERROR - printStackTrace()

当我这样做时

var obj=new BasicDBObject
     while(cursor.hasNext)
     {
       //var cur=cursor.next()
       obj=cursor.next().asInstanceOf[BasicDBObject]

       var id=obj.getString("GroupUuid").toInt
       log.info("GroupUuid"+id)
     }
   }

然后在控制台上打印GroupUuid的值我如何获取TotalArtShares价值请帮助我，我做错了，请指导我

Answer 1

我现在没有Scala的任何东西，但一般的Java技术是首先通过它的顶级键获取文档，然后从底层对象访问属性：

    MongoClient client = new MongoClient(new ServerAddress("192.168.2.4", 27017));
    MongoDatabase mongoDatabase = client.getDatabase("test");

    MongoCollection<Document> trash = mongoDatabase.getCollection("trash");
    MongoCursor<Document> cursor = trash.find().iterator();

    // { "_id" : ObjectId("55dad435d622c0483e94d3b2"), "something" : { "nested" : 1 } } 

    while ( cursor.hasNext() ) {
        Document doc = cursor.next();
        Document something = doc.get("something", Document.class);
        Double nested = something.getDouble("nested");
        System.out.println(nested);
    }

"dot notation"概念是MongoDB在内部处理嵌入数据的方式，并不一定将您选择的语言翻译为在repsonses中访问返回的数据结构的方法。

一旦将事物作为本机对象返回，则由语言构成如何操作它们，并且“点符号”之类的内容不再适用，除非您正在构建查询。

Answer 2

我假设您正在使用来自scala的java mongodb驱动程序，

val cursor=collection.find(new BasicDBObject("ArtShare.TotalArtShares", 0))
  var obj: BasicDBObject= _

  while(cursor.hasNext) {
    obj = cursor.next().asInstanceOf[BasicDBObject]

    val artShare = obj.get("ArtShare").asInstanceOf[BasicDBObject]
    val id = artShare.getInt("TotalArtShares")
    log.info("TotalArtShares " + id)

  }

第一个语句是查询，然后在while循环中检索嵌入文档“ArtShare”并获取字段“TotalArtShares”。

我建议你使用cashbah，这是scala包装器构建在java驱动程序之上，它暴露scala api。

如何在mongodb

2 个答案: