This is how you can make a simple ajax request from your jsp file to some java code:
Returning String as plain text
The jsp page:
<!DOCTYPE html>
<html lang="en">
<head>
<title>SO question 4112686</title>
<script src="http://code.jquery.com/jquery-latest.min.js"></script>
<script>
$(document).on("click", "#somebutton", function() { // When HTML DOM "click" event is invoked on element with ID "somebutton", execute the following function...
$.get("someservlet", function(responseText) { // Execute Ajax GET request on URL of "someservlet" and execute the following function with Ajax response text...
$("#somediv").text(responseText); // Locate HTML DOM element with ID "somediv" and set its text content with the response text.
});
});
</script>
</head>
<body>
<button id="somebutton">press here</button>
<div id="somediv"></div>
</body>
</html>
Servlet doGet() method:
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String text = "some text";
//you can write whatever java code you want to have here, and you can pass the results to the jsp file through the response writer. (text) This will only work from simple strings. If you want to pass more complicated information like lists or objects you will need to convert it to a json object
response.setContentType("text/plain"); // Set content type of the response so that jQuery knows what it can expect.
response.setCharacterEncoding("UTF-8"); // You want world domination, huh?
response.getWriter().write(text); // Write response body.
}
If you want to do it in a form you can do it like this:
Ajaxifying an existing form
<form id="someform" action="someservlet" method="post">
<input type="text" name="foo" />
<input type="text" name="bar" />
<input type="text" name="baz" />
<input type="submit" name="submit" value="Submit" />
</form>
<script>
$(document).on("submit", "#someform", function(event) {
var $form = $(this);
$.post($form.attr("action"), $form.serialize(), function(response) {
// ...
});
event.preventDefault(); // Important! Prevents submitting the form.
});
</script>
Servlet:
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String foo = request.getParameter("foo");
String bar = request.getParameter("bar");
String baz = request.getParameter("baz");
//do some java stuff here
//then return whatever you want
response.setContentType("text/plain");
response.setCharacterEncoding("UTF-8"); /
response.getWriter().write("hello world");
}
Examples taken from: How to use Servlets and Ajax
