It is possible to define a custom attribute that may be referenced in predicates, queries and indexes.
A custom attribute is a "synthetic" attribute that does not exist as a field or a getter in the object that it is extracted from.
Thus, it is necessary to define the policy on how the attribute is supposed to be extracted.
Currently the only way to extract a custom attribute is to implement a com.hazelcast.query.extractor.ValueExtractor
that encompasses the extraction logic.
Custom Attributes are compatible with all Hazelcast serialization methods, including the Portable serialization.