Setting custom java object variable in engine api


I have a problem in initializing custom java object variable in engine api. Steps that I've done are:
1. Made a new class in eclipse which implements Serializable
2. Added custom jar which includes this class in bonita studio
3. Configured this jar as a process dependency
4. Created new pool variable of this class type
When I try to assign value to this variable in java code I receive following exception:
com.thoughtworks.xstream.converters.ConversionException: :
---- Debugging information ----
message :
cause-exception : com.thoughtworks.xstream.mapper.CannotResolveClassException
cause-message :
class : java.util.HashMap
required-type : java.util.HashMap
converter-type : com.thoughtworks.xstream.converters.collections.MapConverter
path : /object-array/map/entry[2]/
line number : 50
class[1] : [Ljava.lang.Object;
converter-type[1] : com.thoughtworks.xstream.converters.collections.ArrayConverter
version : null

Any help would be highly appreciated.

No answers yet.