how to write text into Gmail Message Body by other browser

I would like to do the following:

1. Open a web page → login gmail → compose mail
2. Open other web page →　Select a bookmark, open a java webapp(worked in tomcat)
3. The 开发者_运维问答webapp will copy some text into the above Gmail's Message Body

●if the two pages are different tabs in same browser , is it possible?

●bookmark uses bookmarklet(javascript).

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You can try formulating something like this

http://mail.google.com/mail/?view=cm&fs=1&to=toaddress@domail.com&su=Subject&body=message&ui=1

and open it in a browser.

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I don't think that's at all possible. You're talking about completely different applications.

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I am not sure this is possible without exploiting any browser security flaws. A web app opened in a browser shouldn't be able to interact with anything on your computer, and especially an other browser window.