I have a http request that auto generates '_token' value with the request(this value generated under http request only, not in the response of this request) and this '_token' value needs to be passed to the next http request header as 'authorization'. I know we can use JSON/RegEx post processor if it is in Response of the first http request. However how it be be correlated if the dynamic value is in http request.
Please suggest how can we achieve this in jmeter.
Most likely you are trying to load test an application which uses OAuth and depending on OAuth version and your application setup there could be different options. If the token is permanent - you can just put it into HTTP Header Manager, however if the token expires more or less frequently - you will need to implement OAuth flow using JMeter (in some cases you will need some extras like scripting, kick off browser to open a redirect URL or use OAuth client libraries). Check out How to Run Performance Tests on OAuth Secured Apps with JMeter article for details.
I would suggest contacting your application developers to learn about OAuth version, settings, required client id/secret, etc.
