How exactly can i use application links to link my app with someones jira account

I was trying to login a Jira user on my app. I found about application links to connect external apps with the jira account.
Now I could not find anything how exactly I can login the user and get data like issues, projects etc from the client side.

@KATHANdesai welcome to the Atlassian developer community.

All docs about the application links are pretty old so they are rough around the edges (maybe a little in the middle too). The trick is knowing that application links are really OAuth 1.0a. I assume you are on Jira Server or Data Center because, while OAuth 1.0a exists in Cloud, you really should use OAuth 2.0 instead (or just API tokens).

thanks, @ibuchanan for replying. so if I got it correct for Jira server I will have to make a java app as my client and for the cloud, I can make a nodejs server using which I can send a user the link to allow me to use their data and simply make API calls?
Also if I am correct a cloud user cannot have a URL as jira.something.com it will always be something.altassian.net.
I guess the custom domain will be only allowed for Jira server users. so I want them to connect to my app I will have to use OAuth 1.0a
It would be great if you could just clarify these things for me.

@KATHANdesai,

The explanation and examples are all in Java. And, while I wouldn’t be able to explain how to use Node.js, I know that OAuth 1.0a does not require Java. It is possible but I don’t have any documentation links to explain how.

You are correct that Jira Cloud does not currently allow for custom domains.