This is my first time working with the Mongo Scala driver (version 2.1) and I am noticing odd behavior in the handling of some of my case classes -- some of them are not being recognized as such in the classToCaseClassMap with the result that decoding data for one of them goes down the wrong path and ends with the error java.util.NoSuchElementException: head of empty list at line 204 in org.mongodb.scala.bson.codecs.macrocodecs.MacroCodec because the fieldClazzTypeArgs list is empty.
Here is the top third or so of the stacktrace:
error: class java.util.NoSuchElementException: head of empty list
scala.collection.immutable.Nil$.head(List.scala:420)
scala.collection.immutable.Nil$.head(List.scala:417)
org.mongodb.scala.bson.codecs.macrocodecs.MacroCodec$class.readDocument(MacroCodec.scala:204)
palladium.calendar.dal.mongodb.Implicits$$anon$2$GoogleCalendarEventMacroCodec$3.readDocument(GoogleCalendarDAO.scala:55)
org.mongodb.scala.bson.codecs.macrocodecs.MacroCodec$class.readValue(MacroCodec.scala:173)
palladium.calendar.dal.mongodb.Implicits$$anon$2$GoogleCalendarEventMacroCodec$3.readValue(GoogleCalendarDAO.scala:55)
org.mongodb.scala.bson.codecs.macrocodecs.MacroCodec$class.decode(MacroCodec.scala:104)
palladium.calendar.dal.mongodb.Implicits$$anon$2$GoogleCalendarEventMacroCodec$3.decode(GoogleCalendarDAO.scala:55)
org.mongodb.scala.bson.codecs.macrocodecs.MacroCodec$class.readDocument(MacroCodec.scala:197)
palladium.calendar.dal.mongodb.Implicits$$anon$8$GoogleCalendarMacroCodec$3.readDocument(GoogleCalendarDAO.scala:61)
org.mongodb.scala.bson.codecs.macrocodecs.MacroCodec$class.readValue(MacroCodec.scala:173)
palladium.calendar.dal.mongodb.Implicits$$anon$8$GoogleCalendarMacroCodec$3.readValue(GoogleCalendarDAO.scala:61)
org.mongodb.scala.bson.codecs.macrocodecs.MacroCodec$class.readArray(MacroCodec.scala:187)
palladium.calendar.dal.mongodb.Implicits$$anon$8$GoogleCalendarMacroCodec$3.readArray(GoogleCalendarDAO.scala:61)
org.mongodb.scala.bson.codecs.macrocodecs.MacroCodec$class.readValue(MacroCodec.scala:174)
palladium.calendar.dal.mongodb.Implicits$$anon$8$GoogleCalendarMacroCodec$3.readValue(GoogleCalendarDAO.scala:61)
org.mongodb.scala.bson.codecs.macrocodecs.MacroCodec$class.decode(MacroCodec.scala:104)
palladium.calendar.dal.mongodb.Implicits$$anon$8$GoogleCalendarMacroCodec$3.decode(GoogleCalendarDAO.scala:61)
com.mongodb.operation.CommandResultArrayCodec.decode(CommandResultArrayCodec.java:52)
com.mongodb.operation.CommandResultDocumentCodec.readValue(CommandResultDocumentCodec.java:53)
org.bson.codecs.BsonDocumentCodec.decode(BsonDocumentCodec.java:84)
org.bson.codecs.BsonDocumentCodec.decode(BsonDocumentCodec.java:41)
org.bson.codecs.configuration.LazyCodec.decode(LazyCodec.java:47)
org.bson.codecs.BsonDocumentCodec.readValue(BsonDocumentCodec.java:101)
com.mongodb.operation.CommandResultDocumentCodec.readValue(CommandResultDocumentCodec.java:56)
org.bson.codecs.BsonDocumentCodec.decode(BsonDocumentCodec.java:84)
org.bson.codecs.BsonDocumentCodec.decode(BsonDocumentCodec.java:41)
com.mongodb.connection.ReplyMessage.<init>(ReplyMessage.java:57)
com.mongodb.connection.CommandProtocol.getResponseDocument(CommandProtocol.java:139)
com.mongodb.connection.CommandProtocol.access$000(CommandProtocol.java:51)
com.mongodb.connection.CommandProtocol$CommandResultCallback.callCallback(CommandProtocol.java:271)
com.mongodb.connection.ResponseCallback.onResult(ResponseCallback.java:48)
com.mongodb.connection.ResponseCallback.onResult(ResponseCallback.java:23)
com.mongodb.connection.DefaultConnectionPool$PooledConnection$2.onResult(DefaultConnectionPool.java:470)
com.mongodb.connection.DefaultConnectionPool$PooledConnection$2.onResult(DefaultConnectionPool.java:464)
com.mongodb.connection.UsageTrackingInternalConnection$3.onResult(UsageTrackingInternalConnection.java:119)
com.mongodb.connection.UsageTrackingInternalConnection$3.onResult(UsageTrackingInternalConnection.java:115)
com.mongodb.internal.async.ErrorHandlingResultCallback.onResult(ErrorHandlingResultCallback.java:49)
com.mongodb.connection.InternalStreamConnection.executeCallbackAndReceiveResponse(InternalStreamConnection.java:378)
com.mongodb.connection.InternalStreamConnection.access$1700(InternalStreamConnection.java:66)
com.mongodb.connection.InternalStreamConnection$ResponseBuffersCallback.onResult(InternalStreamConnection.java:420)
com.mongodb.connection.InternalStreamConnection$ResponseBuffersCallback.onResult(InternalStreamConnection.java:389)
com.mongodb.connection.InternalStreamConnection$ResponseHeaderCallback.onSuccess(InternalStreamConnection.java:562)
com.mongodb.connection.InternalStreamConnection$ResponseHeaderCallback.access$2200(InternalStreamConnection.java:517)
com.mongodb.connection.InternalStreamConnection$ResponseHeaderCallback$ResponseBodyCallback.onResult(InternalStreamConnection.java:584)
com.mongodb.connection.InternalStreamConnection$ResponseHeaderCallback$ResponseBodyCallback.onResult(InternalStreamConnection.java:568)
com.mongodb.connection.InternalStreamConnection$3.completed(InternalStreamConnection.java:447)
com.mongodb.connection.InternalStreamConnection$3.completed(InternalStreamConnection.java:444)
com.mongodb.connection.AsynchronousSocketChannelStream$BasicCompletionHandler.completed(AsynchronousSocketChannelStream.java:218)
com.mongodb.connection.AsynchronousSocketChannelStream$BasicCompletionHandler.completed(AsynchronousSocketChannelStream.java:201)
sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126)
sun.nio.ch.Invoker.invokeDirect(Invoker.java:157)
sun.nio.ch.UnixAsynchronousSocketChannelImpl.implRead(UnixAsynchronousSocketChannelImpl.java:553)
sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:276)
sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:297)
My application models someone's Google calendar. Here are my case classes:
case class GoogleDateTime(date: Option[DateTime] = None, dateTime: Option[DateTime])
case class LongId(id: Long)
case class GoogleCalendarEvent(id: String,
status: Option[String] = None,
htmlLink: Option[String] = None,
created: Option[DateTime] = None,
updated: Option[DateTime] = None,
creator: Option[GoogleWho] = None,
organizer: Option[GoogleWho] = None,
summary: Option[String],
description: Option[String] = None,
location: Option[String] = None,
start: GoogleDateTime,
end: GoogleDateTime,
extendedProperties: Option[GoogleEventExtendedProperties] = None)
case class GoogleCalendarEventList(nextPageToken: Option[String],
items: Option[List[GoogleCalendarEvent]])
case class GoogleWho(email: Option[String],
displayName: Option[String])
case class GoogleEventSharedProperties(createdBy: Option[String] = None,
sessionType: Option[String] = None,
sessionId: Option[LongId] = None,
locationId: Option[LongId] = None,
roomId: Option[LongId] = None)
case class GoogleEventExtendedProperties(shared: Option[GoogleEventSharedProperties])
Here is a link to a screenshot showing the contents of the classToCaseClassMap at the point where the error occurs.
The screenshot shows a map with six items, including four of my case classes: GoogleCalendarEvent, GoogleWho, GoogleDateTime, and GoogleEventExtendedProperties. Only the first of these (GoogleCalendarEvent) is properly identified as a case class.
I tried making the problematic classes sealed but that didn't help.
Here is how I create the CodecRegistry:
val dtMap = Map(BsonType.DATE_TIME -> classOf[DateTime])
val typeClassReplacedMap = new BsonTypeClassMap(JavaConversions.mapAsJavaMap(dtMap))
val gcCodecProvider = new DocumentCodecProvider(typeClassReplacedMap)
implicit val gcRegistry: CodecRegistry = fromRegistries(fromCodecs(dtCodec),
fromProviders( gcCodecProvider,
classOf[GoogleCalendarEvent],
classOf[GoogleDateTime],
classOf[LongId],
classOf[GoogleEventExtendedProperties],
classOf[GoogleEventSharedProperties],
classOf[GoogleWho],
classOf[GoogleCalendar]),
DEFAULT_CODEC_REGISTRY )
Here is a gist showing the data access code and how I am using it (in an sbt console or Intellij IDEA Scala console).
The app I am refactoring has been working fine with the Reactive Mongo version 0.11.7 but we need to migrate it to the officially supported Mongo Scala driver in order to use a new Atlas database.
FWIW after that time, have a look at https://jira.mongodb.org/browse/SCALA-338
I have the same issue, thanks to your post I found out that it's somehow the ordering of the codec providers.
Initially I though it could be solved by making sure that case classes that hold values of other case class types are listed before these other cases classes. But by now even that did not solve my issue anymore, but maybe it can help solve your specific situation.
Simply downgrading from 2.1.0 to 2.0.0 fixed the issue for me.