// random send one task
this.random = new Random();
grouperType = GrouperType.none;
} else if (Grouping._Fields.CUSTOM_OBJECT.equals(fields)) {
// user custom grouping by JavaObject
JavaObject jobj = thrift_grouping.get_custom_object();
CustomStreamGrouping g = Thrift.instantiateJavaObject(jobj);
int myTaskId = topology_context.getThisTaskId();
String componentId = topology_context.getComponentId(myTaskId);
GlobalStreamId stream = new GlobalStreamId(componentId, streamId);
custom_grouper = new MkCustomGrouper(topology_context, g, stream,