Watch inbox and reply for incoming mail using GMAIL API

I want to listen to the inbox, and when a new message arrives, I want to read the data of the unseen messages using GMAIL API. I need to read the incoming mail because I want to send a reply mail. (i.e) I am developing a mail service for my web application (servlet).

The part which I tried is that I went through GMAIL API documentation, and I found that the watch method in Gmail API is useful for listening to the users' inbox. Still, I don't understand how to use the watch method, so my servlet gets a push notification on new incoming mail and reads the new incoming mail.

Can anyone tell me the steps to achieve this?

I'm assuming that you read the same documentation that I just found. Push Notifications So, that's what you should do. It is not practical to ask somebody what you should do, when you already have documentation which tells you what to do, but no doubt you ran into some confusion when you tried to work through the documentation. It is quite long, after all.

So it would be more practical for you to explain where you got stuck when trying to read the documentation. Tell us what you did so far, for example, and what problems you had with that.