HttpClient 5.0 migration guide is a third party resource with recommendations about the upgrade process and possible upgrade paths from Apache HttpClient 4.x to Apache HttpClient 5.x.
Asynchronous JSON message processors library is a companion project for HttpClient 5.0 developed outside the Apache Software Foundation.
The library provides a number of asynchronous message consumers and producers for efficient, reactive processing of HTTP messages with enclosed JSON content using Jackson JSON processor.
Android extensions for Apache HttpClient 5.x is a third party library that provides extra functionality simplifying application of Apache HttpClient on Google Android platform.