selector property
Selects one or more request or response message fields to apply this
FieldPolicy.
When a FieldPolicy is used in proto annotation, the selector must
be left as empty. The service config generator will automatically fill
the correct value.
When a FieldPolicy is used in service config, the selector must be a
comma-separated string with valid request or response field paths,
such as "foo.bar" or "foo.bar,foo.baz".
Implementation
final String selector;