How to fix the URI does not specify a valid host name in ClientProtocolException:

You just need to add http:// at the beginning of the URI.

If you are seeing the same error in JMeter while you want to use a response Json key value in another variable(by creating a new HTTP Request) then use JSON Extractor instead of Regular Expression extractor. Thread Group->Right click and Add->Post Processor->JSON Extractor)enter image description here