Key

Encapsulates the type, name and empty value for a context entry. All reads and writes from a context instance must be done using a context key, which will ensure the right type is used on both operations. The key's name is used when configuring mappings and incoming/outgoing/returning codecs for context propagation across channels.

If you try to read an entry from a context and such entry is not present, the empty value for the key is returned instead.