You can't. JSP runs on the server, Javascript (which is NOT Java) runs on the client. You might want to look into something like AJAX which will allow your javascript to make a complete connection to the server, receive data, and then update your page, which will make it look like you are doing what you are asking, but it takes longer than a true programmatic connection.
P.S. Don't come back and ask for more info concerning AJAX. That is another thing does not belong on this forum.
Java Programmer and Sun Systems Administrator
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Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it.
--Brian Kernighan