JsonMappingException: Already had POJO for id

To avoid id conflict try to use ObjectIdGenerators.PropertyGenerator.class or ObjectIdGenerators.UUIDGenerator.class instead of ObjectIdGenerators.IntSequenceGenerator.class

You should use scope parameter when annotating the ids. Then the de-serializer would make sure the id is unique within the scope.

From Annotation Type JsonIdentityInfo:

Scope is used to define applicability of an Object Id: all ids must be unique within their scope; where scope is defined as combination of this value and generator type.

e.g.

@JsonIdentityInfo(generator=ObjectIdGenerators.IntSequenceGenerator.class,property="@id", scope = Account.class)