This is a bugfix release to address mainly the following things:

#1191 race conditions in data loader dispatching #1182 fix null element #1150 class cast exception in schema generation #1142 validate input variables #1113 npe in field tracking during dispatch #1159 fix json encoding of values

See https://github.com/graphql-java/graphql-java/pulls?q=is%3Apr+milestone%3A9.3