Hi @david.pinn & @daniel,
I got the solution. I need to pass basic authentication of JIRA user in header of third party api client then i can able to get logged in user by below methods. Thanks to all.
Request xml of thirrd part api which is calling JIRA Rest service:
Note: You need to do base64 encode of your username and password in below format:
Example: username:password
Code to get logged in user:
ApplicationUser user = ComponentAccessor.getJiraAuthenticationContext().getLoggedInUser();
Now i am able to create JIRA issues by third party api.