Several ways:
-
Use
window.location
to fire a GET request. Caveat is that it”s synchronous (so the client will see the current page being changed).window.location = "http://example.com/servlet?key=" + encodeURIComponent(key);
Note the importance of built-in
encodeURIComponent()
function to encode the request parameters before passing it. -
Use
form.submit()
to fire a GET or POST request. The caveat is also that it”s synchronous.document.formname.key.value = key; document.formname.submit();
With
<form name="formname" action="servlet" method="post"> <input type="hidden" name="key"> </form>
Alternatively you can also only set the hidden field of an existing form and just wait until the user submits it.
-
Use
XMLHttpRequest#send()
to fire an asynchronous request in the background (also known as Ajax). Below example will invoke servlet”sdoGet()
.var xhr = new XMLHttpRequest(); xhr.open("GET", "http://example.com/servlet?key=" + encodeURIComponent(key)); xhr.send(null);
Below example will invoke servlet”s
doPost()
.var xhr = new XMLHttpRequest(); xhr.open("POST", "http://example.com/servlet"); xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded"); xhr.send("key=" + encodeURIComponent(key));
-
Use jQuery to send a crossbrowser compatible Ajax request (above
xhr
code works in real browsers only, for MSIE compatibility, you”ll need to add some clutter 😉 ).$.get("http://example.com/servlet", { "key": key });
$.post("http://example.com/servlet", { "key": key });
Note that jQuery already transparently encodes the request parameters all by itself, so you don”t need
encodeURIComponent()
here.
Either way, the key
will be just available by request.getParameter("key")
in the servlet.