kotlin ktor中出现BsonInvalidOperationException异常错误

k97glaaz  于 2022-11-30  发布在  Kotlin
关注(0)|答案(1)|浏览(125)

作为MongoDB的新手，我目前正在将kMongo库集成到我的ktor项目中，并试图创建一个数据库来读写事件模型。
按照object mapping in the kMongo user manual的说明，我创建了一个mongoId字段，它被序列化为一个名为_id的String。
我的事件模型是一个数据类，嵌套在密封类中，但由KotlinX-Serialization正确序列化。该模型如下所示：

sealed class Event {
    @SerialName("_id") abstract val mongoId: String
    abstract val id: ID.Event
    abstract val dateTime: LocalDateTime

    fun asString() = id.toString()

    sealed class Hiring : Event() {
        @SerialName("_id") abstract override val mongoId: String
        abstract override val id: ID.Event
        abstract override val dateTime: LocalDateTime

        @Serializable
        data class Start(
            override val id: ID.Event,
            override val dateTime: LocalDateTime,
            val hiringDetailsId: ID.HiringDetails
        ) : Hiring() {
            @SerialName("_id") override val mongoId: String = id.asString()
        }
        ...

在一个仓库类中，我初始化MongoDB，并在一个集合上使用通用的、无参数的find()从数据库中检索所有Event模型：

...
    private val kmongo = KMongo.createClient().coroutine.client
    private val db = kmongo.getDatabase("test")
    private val eventCollection = db.getCollection<Event>().coroutine
    ...
    override suspend fun getAllEvents() = eventCollection.find().toList()

然后在Main类中，尝试在单击触发器上加载Event数据：

...
val id = ID.Event(UUID())
...
it.on.click {
   runBlocking {
      val events = eventRepo.getAllEvents().toString()
      logger.debug { events }
   }
}

奇怪的部分从这里开始，服务器正确启动，MongoDB正确初始化，但当我尝试在点击触发器上读取时，出现以下错误：

org.bson.BsonInvalidOperationException: readString can only be called when CurrentBSONType is STRING, not when CurrentBSONType is DOCUMENT.
    at org.bson.AbstractBsonReader.verifyBSONType(AbstractBsonReader.java:689)
    at org.bson.AbstractBsonReader.checkPreconditions(AbstractBsonReader.java:721)
    at org.bson.AbstractBsonReader.readString(AbstractBsonReader.java:456)
    at com.github.jershell.kbson.FlexibleDecoder.decodeString(BsonFlexibleDecoder.kt:130)
    at kotlinx.serialization.encoding.AbstractDecoder.decodeStringElement(AbstractDecoder.kt:58)
    at kotlinx.serialization.internal.AbstractPolymorphicSerializer.deserialize(AbstractPolymorphicSerializer.kt:52)
    at kotlinx.serialization.encoding.Decoder$DefaultImpls.decodeSerializableValue(Decoding.kt:257)
    at kotlinx.serialization.encoding.AbstractDecoder.decodeSerializableValue(AbstractDecoder.kt:16)
    at org.litote.kmongo.serialization.SerializationCodec.decode(SerializationCodec.kt:66)
    at com.mongodb.internal.operation.CommandResultArrayCodec.decode(CommandResultArrayCodec.java:52)
    at com.mongodb.internal.operation.CommandResultDocumentCodec.readValue(CommandResultDocumentCodec.java:60)
    at org.bson.codecs.BsonDocumentCodec.decode(BsonDocumentCodec.java:87)
    at org.bson.codecs.BsonDocumentCodec.decode(BsonDocumentCodec.java:42)
    at org.bson.internal.LazyCodec.decode(LazyCodec.java:48)
    at org.bson.codecs.BsonDocumentCodec.readValue(BsonDocumentCodec.java:104)
    at com.mongodb.internal.operation.CommandResultDocumentCodec.readValue(CommandResultDocumentCodec.java:63)
    at org.bson.codecs.BsonDocumentCodec.decode(BsonDocumentCodec.java:87)
    at org.bson.codecs.BsonDocumentCodec.decode(BsonDocumentCodec.java:42)
    at com.mongodb.internal.connection.ReplyMessage.<init>(ReplyMessage.java:51)
    at com.mongodb.internal.connection.InternalStreamConnection.getCommandResult(InternalStreamConnection.java:535)
    at com.mongodb.internal.connection.InternalStreamConnection.access$500(InternalStreamConnection.java:86)
    at com.mongodb.internal.connection.InternalStreamConnection$2$1.onResult(InternalStreamConnection.java:520)
    at com.mongodb.internal.connection.InternalStreamConnection$2$1.onResult(InternalStreamConnection.java:498)
    at com.mongodb.internal.connection.InternalStreamConnection$MessageHeaderCallback$MessageCallback.onResult(InternalStreamConnection.java:821)
    at com.mongodb.internal.connection.InternalStreamConnection$MessageHeaderCallback$MessageCallback.onResult(InternalStreamConnection.java:785)
    at com.mongodb.internal.connection.InternalStreamConnection$5.completed(InternalStreamConnection.java:645)
    at com.mongodb.internal.connection.InternalStreamConnection$5.completed(InternalStreamConnection.java:642)
    at com.mongodb.internal.connection.AsynchronousChannelStream$BasicCompletionHandler.completed(AsynchronousChannelStream.java:250)
    at com.mongodb.internal.connection.AsynchronousChannelStream$BasicCompletionHandler.completed(AsynchronousChannelStream.java:233)
    at java.base/sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:129)
    at java.base/sun.nio.ch.Invoker.invokeDirect(Invoker.java:160)
    at java.base/sun.nio.ch.UnixAsynchronousSocketChannelImpl.implRead(UnixAsynchronousSocketChannelImpl.java:573)
    at java.base/sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:276)
    at java.base/sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:297)
    at com.mongodb.internal.connection.AsynchronousSocketChannelStream$AsynchronousSocketChannelAdapter.read(AsynchronousSocketChannelStream.java:144)
    at com.mongodb.internal.connection.AsynchronousChannelStream.readAsync(AsynchronousChannelStream.java:118)
    at com.mongodb.internal.connection.AsynchronousChannelStream.readAsync(AsynchronousChannelStream.java:107)
    at com.mongodb.internal.connection.InternalStreamConnection.readAsync(InternalStreamConnection.java:642)
    at com.mongodb.internal.connection.InternalStreamConnection.access$600(InternalStreamConnection.java:86)
    at com.mongodb.internal.connection.InternalStreamConnection$MessageHeaderCallback.onResult(InternalStreamConnection.java:775)
    at com.mongodb.internal.connection.InternalStreamConnection$MessageHeaderCallback.onResult(InternalStreamConnection.java:760)
    at com.mongodb.internal.connection.InternalStreamConnection$5.completed(InternalStreamConnection.java:645)
    at com.mongodb.internal.connection.InternalStreamConnection$5.completed(InternalStreamConnection.java:642)
    at com.mongodb.internal.connection.AsynchronousChannelStream$BasicCompletionHandler.completed(AsynchronousChannelStream.java:250)
    at com.mongodb.internal.connection.AsynchronousChannelStream$BasicCompletionHandler.completed(AsynchronousChannelStream.java:233)
    at java.base/sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:129)
    at java.base/sun.nio.ch.UnixAsynchronousSocketChannelImpl.finishRead(UnixAsynchronousSocketChannelImpl.java:447)
    at java.base/sun.nio.ch.UnixAsynchronousSocketChannelImpl.finish(UnixAsynchronousSocketChannelImpl.java:195)
    at java.base/sun.nio.ch.UnixAsynchronousSocketChannelImpl.onEvent(UnixAsynchronousSocketChannelImpl.java:217)
    at java.base/sun.nio.ch.KQueuePort$EventHandlerTask.run(KQueuePort.java:312)
    at java.base/sun.nio.ch.AsynchronousChannelGroupImpl$1.run(AsynchronousChannelGroupImpl.java:113)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
    at java.base/java.lang.Thread.run(Thread.java:833)

根据stacktrace，BSON过滤部分似乎出了问题，尽管没有。当我使用MongoDB compass验证数据库中的对象时，我可以看到所有的东西都初始化了，并且写得非常好：

普通的id字段在我的软件内部作为ID.Event对象类型使用，而_id由Mongo内部使用。
谁能告诉我潜在的问题是什么？

kotlin

1条答案

按热度按时间
n1bvdmb6

n1bvdmb61#

我对Kotlin不熟悉，但我想更深入地探讨一下：
如果第二次没有展开，Mongo Compass可能会显示_id或id字段，以包含括号{，而这些字段当前按预期Map（_id为String，id为对象）。
为了确认，您的文档的当前结构是（例如here in the playground）：

{
  _id: "7d51",
  id: {
    id: "7d51"
  },
  hiringDetailsId: {
    id: "8392"
  }
}

我们可以在Compass的屏幕截图中看到，其中_id字段显示的值直接为字符串，而其他两个字段显示的值为对象（每个都包含{ id: "<string>" }值）。
该错误明确指出代码需要一个字符串，但却找到了一个文档：

BsonInvalidOperationException: readString can only be called when CurrentBSONType is STRING, not when CurrentBSONType is DOCUMENT.

我不能说内部的解包，但我确实感觉嵌套的id.id（可能还有hiringDetailsId.id）是这里的问题。即使它没有直接相关，这似乎是一个简化模式的机会，除非有令人信服的理由引入额外的嵌套层。

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