This seems to be broken with Bolt. It works fine with an embedded Neo4j connection.

We have a field defined as:

@ElementCollection(fetch = FetchType.EAGER)
private java.util.Map<String,MockEmbedded> mapOfEmbedded;

MockEmbedded is annotated with @Embeddable, and contains two fields of types int (value1) and String (value2). The latter was left null for this test.

The data seems to be written to the database, though the result seems suspect (not sure what it's suppose to look like though):
- itcreates an edge, with label 'mapOfEmbedded', from entity with property mapOfEmbedded_KEY=<key>
- to a node, with label '<entityname>_mapOfEmbedded' and no properties
- another edge, with label 'value', and no properties
- to a node, with only the label 'EMBEDDED', and a property value1=<value>

Seems like that intermediate node might be superfluous, or maybe there's a good reason for it.

And I don't know what it looks like in the db when I use an embedded Neo4j connection. I'm not sure of an easy way to extract that information.

Plain embedded, and List<embedded>, fields work fine with both connection types.

In case it's useful, here's the relevant part of the trace logs while using Bolt:

08:25:23.100 [Test worker] DEBUG o.h.o.p.impl.OgmCollectionPersister - Inserting collection: [com.nokia.nspos.model.domain.mock.entities.MockEntity.mapOfEmbedded#262]
08:25:23.100 [Test worker] TRACE o.h.o.t.d.impl.BasicGridBinder - binding [262] to parameter(s) [mock_MockEntity_dbId]
08:25:23.100 [Test worker] TRACE o.h.o.t.d.impl.BasicGridBinder - binding [equip] to parameter(s) [mapOfEmbedded_KEY]
08:25:23.100 [Test worker] TRACE o.h.o.t.d.impl.BasicGridBinder - binding [2] to parameter(s) [mapOfEmbedded.value.value1]
08:25:23.100 [Test worker] TRACE o.h.o.t.d.impl.BasicGridBinder - binding [null] to parameter [mapOfEmbedded.value.value2]
08:25:23.101 [Test worker] TRACE o.h.o.t.d.impl.BasicGridBinder - binding [262] to parameter(s) [mock_MockEntity_dbId]
08:25:23.101 [Test worker] TRACE o.h.o.t.d.impl.BasicGridBinder - binding [262] to parameter(s) [dbId]
08:25:23.103 [Test worker] TRACE org.hibernate.ogm.datastore.access - Reading association with key AssociationKey(mock_MockEntity_mapOfEmbedded) [mock_MockEntity_dbId=262] from datastore and context AssociationContextImpl [associationTypeContext=AssociationContext [optionsContext=OptionsContextImpl [entityType=class com.nokia.nspos.model.domain.mock.entities.MockEntity, propertyName=mapOfEmbedded]], operationsQueue=null, entityTuple=TuplePointer[Tuple[mockFloat=0.0, mockString=mock, mockEnum2=1, mockEnum=0, mockTimestamp=1459399611000, mockLong2=0, _modelVersion=1.0.1, mockEnum3=0, mockLong=1, mockBoolean2=false, anotherSource.namespace=sam, mockInt=1, anotherSource.fdn=abc:def, dbId=262, mockFloat2=0.0, singleEmbedded.value1=3, DTYPE=mock_MockEntity, singleEmbedded.value2=hello, _version=0, myFloat=0.0, superValue1=0, mockBoolean=false, nativeMockInt=1, mockBigInt=10, mockTimestamp2=0, anotherSource.scheme=1, mockBigInt2=10]]]
08:25:23.197 [Test worker] TRACE o.h.o.t.d.impl.BasicGridBinder - binding [262] to parameter(s) [mock_MockEntity_dbId]
08:25:23.197 [Test worker] TRACE o.h.o.t.d.impl.BasicGridBinder - binding [fm] to parameter(s) [mapOfEmbedded_KEY]
08:25:23.197 [Test worker] TRACE o.h.o.t.d.impl.BasicGridBinder - binding [1] to parameter(s) [mapOfEmbedded.value.value1]
08:25:23.197 [Test worker] TRACE o.h.o.t.d.impl.BasicGridBinder - binding [null] to parameter [mapOfEmbedded.value.value2]
08:25:23.197 [Test worker] TRACE org.hibernate.ogm.datastore.access - Creating association with key AssociationKey(mock_MockEntity_mapOfEmbedded) [mock_MockEntity_dbId=262] in datastore
08:25:23.202 [Test worker] TRACE org.hibernate.ogm.datastore.access - Determining whether association DefaultAssociationKeyMetadata [table=mock_MockEntity_mapOfEmbedded, columnNames=[mock_MockEntity_dbId], isInverse=false, collectionRole=mapOfEmbedded, associationKind=EMBEDDED_COLLECTION, rowKeyColumnNames=[mock_MockEntity_dbId, mapOfEmbedded_KEY], rowKeyIndexColumnNames=[mapOfEmbedded_KEY], associatedEntityKeyMetadata=DefaultAssociatedEntityKeyMetadata [associationKeyColumns=[mapOfEmbedded.value.value1, mapOfEmbedded.value.value2], entityKeyMetadata=DefaultEntityKeyMetadata{table='mock_MockEntity_mapOfEmbedded', columnNames=[mapOfEmbedded.value.value1, mapOfEmbedded.value.value2]}]] is stored in an entity structure
08:25:23.203 [Test worker] DEBUG o.h.o.p.impl.OgmCollectionPersister - done inserting collection: 2 rows inserted


And here it is for Embedded Neo4j:

08:39:47.234 [Test worker] DEBUG o.h.o.p.impl.OgmCollectionPersister - Inserting collection: [com.nokia.nspos.model.domain.mock.entities.MockEntity.mapOfEmbedded#1]
08:39:47.234 [Test worker] TRACE o.h.o.t.d.impl.BasicGridBinder - binding [1] to parameter(s) [mock_MockEntity_dbId]
08:39:47.234 [Test worker] TRACE o.h.o.t.d.impl.BasicGridBinder - binding [equip] to parameter(s) [mapOfEmbedded_KEY]
08:39:47.234 [Test worker] TRACE o.h.o.t.d.impl.BasicGridBinder - binding [2] to parameter(s) [mapOfEmbedded.value.value1]
08:39:47.234 [Test worker] TRACE o.h.o.t.d.impl.BasicGridBinder - binding [null] to parameter [mapOfEmbedded.value.value2]
08:39:47.234 [Test worker] TRACE o.h.o.t.d.impl.BasicGridBinder - binding [1] to parameter(s) [mock_MockEntity_dbId]
08:39:47.235 [Test worker] TRACE o.h.o.t.d.impl.BasicGridBinder - binding [1] to parameter(s) [dbId]
08:39:47.238 [Test worker] TRACE org.hibernate.ogm.datastore.access - Reading association with key AssociationKey(mock_MockEntity_mapOfEmbedded) [mock_MockEntity_dbId=1] from datastore and context AssociationContextImpl [associationTypeContext=AssociationContext [optionsContext=OptionsContextImpl [entityType=class com.nokia.nspos.model.domain.mock.entities.MockEntity, propertyName=mapOfEmbedded]], operationsQueue=null, entityTuple=TuplePointer[Tuple[mockFloat=0.0, mockString=mock, mockEnum2=1, mockEnum=0, mockTimestamp=1459399611000, mockLong2=0, _modelVersion=1.0.1, mockEnum3=0, mockLong=1, mockBoolean2=false, anotherSource.namespace=sam, mockInt=1, anotherSource.fdn=abc:def, dbId=1, mockFloat2=0.0, singleEmbedded.value1=3, DTYPE=mock_MockEntity, singleEmbedded.value2=hello, _version=0, myFloat=0.0, mockBoolean=false, superValue1=0, nativeMockInt=1, mockBigInt=10, mockTimestamp2=0, anotherSource.scheme=1, mockBigInt2=10]]]
08:39:47.260 [Test worker] TRACE o.h.o.d.n.logging.impl.GraphLogger - Found owner node: (:`MOCK_MOCKENTITY`:ENTITY{dbId:1, mockFloat:0.0, mockString:"mock", mockEnum2:1, mockEnum:0, mockTimestamp:1459399611000, mockLong2:0, `_modelVersion`:"1.0.1", mockEnum3:0, mockLong:1, mockBoolean2:false, mockInt:1, mockFloat2:0.0, DTYPE:"mock_MockEntity", myFloat:0.0, `_version`:0, mockBoolean:false, superValue1:0, mockBigInt:"10", nativeMockInt:1, mockTimestamp2:0, mockBigInt2:"10"})
08:39:47.364 [Test worker] TRACE o.h.o.t.d.impl.BasicGridBinder - binding [1] to parameter(s) [mock_MockEntity_dbId]
08:39:47.364 [Test worker] TRACE o.h.o.t.d.impl.BasicGridBinder - binding [fm] to parameter(s) [mapOfEmbedded_KEY]
08:39:47.364 [Test worker] TRACE o.h.o.t.d.impl.BasicGridBinder - binding [1] to parameter(s) [mapOfEmbedded.value.value1]
08:39:47.364 [Test worker] TRACE o.h.o.t.d.impl.BasicGridBinder - binding [null] to parameter [mapOfEmbedded.value.value2]
08:39:47.365 [Test worker] TRACE org.hibernate.ogm.datastore.access - Creating association with key AssociationKey(mock_MockEntity_mapOfEmbedded) [mock_MockEntity_dbId=1] in datastore
08:39:47.422 [Test worker] TRACE o.h.o.d.n.logging.impl.GraphLogger - Created relationship: (:`MOCK_MOCKENTITY`:ENTITY{dbId:1, mockFloat:0.0, mockString:"mock", mockEnum2:1, mockEnum:0, mockTimestamp:1459399611000, mockLong2:0, `_modelVersion`:"1.0.1", mockEnum3:0, mockLong:1, mockBoolean2:false, mockInt:1, mockFloat2:0.0, DTYPE:"mock_MockEntity", myFloat:0.0, `_version`:0, mockBoolean:false, superValue1:0, mockBigInt:"10", nativeMockInt:1, mockTimestamp2:0, mockBigInt2:"10"}) - [mapOfEmbedded{`mapOfEmbedded_KEY`:"equip"}] - (:EMBEDDED:`mock_MockEntity_mapOfEmbedded`)
08:39:47.424 [Test worker] TRACE o.h.o.d.n.logging.impl.GraphLogger - Created relationship: (:`MOCK_MOCKENTITY`:ENTITY{dbId:1, mockFloat:0.0, mockString:"mock", mockEnum2:1, mockEnum:0, mockTimestamp:1459399611000, mockLong2:0, `_modelVersion`:"1.0.1", mockEnum3:0, mockLong:1, mockBoolean2:false, mockInt:1, mockFloat2:0.0, DTYPE:"mock_MockEntity", myFloat:0.0, `_version`:0, mockBoolean:false, superValue1:0, mockBigInt:"10", nativeMockInt:1, mockTimestamp2:0, mockBigInt2:"10"}) - [mapOfEmbedded{`mapOfEmbedded_KEY`:"fm"}] - (:EMBEDDED:`mock_MockEntity_mapOfEmbedded`)
08:39:47.424 [Test worker] TRACE org.hibernate.ogm.datastore.access - Determining whether association DefaultAssociationKeyMetadata [table=mock_MockEntity_mapOfEmbedded, columnNames=[mock_MockEntity_dbId], isInverse=false, collectionRole=mapOfEmbedded, associationKind=EMBEDDED_COLLECTION, rowKeyColumnNames=[mock_MockEntity_dbId, mapOfEmbedded_KEY], rowKeyIndexColumnNames=[mapOfEmbedded_KEY], associatedEntityKeyMetadata=DefaultAssociatedEntityKeyMetadata [associationKeyColumns=[mapOfEmbedded.value.value1, mapOfEmbedded.value.value2], entityKeyMetadata=DefaultEntityKeyMetadata{table='mock_MockEntity_mapOfEmbedded', columnNames=[mapOfEmbedded.value.value1, mapOfEmbedded.value.value2]}]] is stored in an entity structure
08:39:47.424 [Test worker] DEBUG o.h.o.p.impl.OgmCollectionPersister - done inserting collection: 2 rows inserted

I've highlighted the differences.

Thanks for the feedback, I'll look into this

There is definitly something odd about mapping of embedded in Neo4j, I'll fix it for the 5.2 release.

I haven't found any easy way to check the content of an embedded Neo4j db. You can use the Neo4j server and update the configuration to point to the location of the embedded db.
The problem is that only one process at the time can access the embedded db, so. if your application is running the server won't be able to read it and if the server is using it your application won't be able to access it.
I don't think there is a solution for this at the moment but please, let me know if you can find one.