Why Decoder Can Not Be Null?

Hi, I’m trying to figure out why when querying/iterating a model/entity, I’m getting decoder can not be null as shown in the below stack trace? Other entities work, but this particular one isn’t so I’m trying to figure out why it isn’t working. Any ideas?

Caused by: java.lang.IllegalArgumentException: decoder can not be null
	at org.bson.assertions.Assertions.notNull(Assertions.java:35)
	at org.bson.codecs.DecoderContext.decodeWithChildContext(DecoderContext.java:95)
	at dev.morphia.mapping.codec.pojo.EntityDecoder.decodeModel(EntityDecoder.java:65)
	at dev.morphia.mapping.codec.pojo.EntityDecoder.decodeProperties(EntityDecoder.java:87)
	at dev.morphia.mapping.codec.pojo.EntityDecoder.decode(EntityDecoder.java:42)
	at dev.morphia.mapping.codec.pojo.MorphiaCodec.decode(MorphiaCodec.java:66)
	at dev.morphia.mapping.codec.pojo.EntityDecoder.decode(EntityDecoder.java:47)
	at dev.morphia.mapping.codec.pojo.MorphiaCodec.decode(MorphiaCodec.java: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:84)
	at org.bson.codecs.BsonDocumentCodec.decode(BsonDocumentCodec.java:41)
	at org.bson.internal.LazyCodec.decode(LazyCodec.java:48)
	at org.bson.codecs.BsonDocumentCodec.readValue(BsonDocumentCodec.java:101)
	at com.mongodb.internal.operation.CommandResultDocumentCodec.readValue(CommandResultDocumentCodec.java:63)
	at org.bson.codecs.BsonDocumentCodec.decode(BsonDocumentCodec.java:84)
	at org.bson.codecs.BsonDocumentCodec.decode(BsonDocumentCodec.java:41)
	at com.mongodb.internal.connection.ReplyMessage.<init>(ReplyMessage.java:51)
	at com.mongodb.internal.connection.InternalStreamConnection.getCommandResult(InternalStreamConnection.java:412)
	at com.mongodb.internal.connection.InternalStreamConnection.receiveCommandMessageResponse(InternalStreamConnection.java:308)
	at com.mongodb.internal.connection.InternalStreamConnection.sendAndReceive(InternalStreamConnection.java:258)
	at com.mongodb.internal.connection.UsageTrackingInternalConnection.sendAndReceive(UsageTrackingInternalConnection.java:99)
	at com.mongodb.internal.connection.DefaultConnectionPool$PooledConnection.sendAndReceive(DefaultConnectionPool.java:500)
	at com.mongodb.internal.connection.CommandProtocolImpl.execute(CommandProtocolImpl.java:71)
	at com.mongodb.internal.connection.DefaultServer$DefaultServerProtocolExecutor.execute(DefaultServer.java:224)
	at com.mongodb.internal.connection.DefaultServerConnection.executeProtocol(DefaultServerConnection.java:202)
	at com.mongodb.internal.connection.DefaultServerConnection.command(DefaultServerConnection.java:118)
	at com.mongodb.internal.connection.DefaultServerConnection.command(DefaultServerConnection.java:110)
	at com.mongodb.internal.operation.CommandOperationHelper.executeCommand(CommandOperationHelper.java:343)
	at com.mongodb.internal.operation.CommandOperationHelper.executeCommand(CommandOperationHelper.java:334)
	at com.mongodb.internal.operation.CommandOperationHelper.executeCommandWithConnection(CommandOperationHelper.java:220)
	at com.mongodb.internal.operation.FindOperation$1.call(FindOperation.java:631)
	at com.mongodb.internal.operation.FindOperation$1.call(FindOperation.java:625)
	at com.mongodb.internal.operation.OperationHelper.withReadConnectionSource(OperationHelper.java:462)
	at com.mongodb.internal.operation.FindOperation.execute(FindOperation.java:625)
	at com.mongodb.internal.operation.FindOperation.execute(FindOperation.java:77)
	at com.mongodb.client.internal.MongoClientDelegate$DelegateOperationExecutor.execute(MongoClientDelegate.java:190)
	at com.mongodb.client.internal.MongoIterableImpl.execute(MongoIterableImpl.java:135)
	at com.mongodb.client.internal.MongoIterableImpl.iterator(MongoIterableImpl.java:92)
	at dev.morphia.query.MorphiaQuery.prepareCursor(MorphiaQuery.java:320)
	at dev.morphia.query.MorphiaQuery.iterator(MorphiaQuery.java:201)
	at dev.morphia.query.MorphiaQuery.iterator(MorphiaQuery.java:196)

Server Version: MongoDB, 4.0.22
Driver Version: mongo-java-driver|sync, version: "4.0.5" 
Morphia Version: morphia-core, 2.1.4

Note: It is a single node replication cluster using Wired Tiger storage engine.

[evanchooly]

Wow. It would have taken forever to suss that out here. Nice catch. Though it suggests I should add a test for that case. I’m pretty sure there’s a validation for conflicting mappings like that but I’m not sure it checks the cross-inheritance boundary like that.

[iAmcR]

Hi, figured it out. It’s pretty simple, I need to get some sleep!

The problem occurred because I had the repeated the same properties in the abstract class into the concrete class. For example, I had:

   @Property("p")
    public int pathetic;

in Errant and in SErrant. Morphia doesn’t like that and couldn’t determine which to use so essentially no decoder was set for that field.

Thanks a mil for clues and pointing me in the right direction. It’s very appreciated!