request.getQueryString() seems to need some encoding

It really took all day but :

final String param = new String(request.getParameter("param").getBytes(
                "iso-8859-1"), "UTF-8");

See also here. Note that this is valid iff the decoding charset (URIEncoding in tomcat) of the server is iso-8859-1 - otherwise this charset must be passed in. For an example of how to get the URIEncoding charset from the server.xml for Tomcat 7 see my quoted answer

I've run into this same problem before. Not sure what Java servlet container you're using, but at least in Tomcat 5.x (not sure about 6.x) the request.setCharacterEncoding() method doesn't really have an effect on GET parameters. By the time your servlet runs, GET parameters have already been decoded by Tomcat, so setCharacterEncoding won't do anything.

Two ways to get around this:

1. Change the URIEncoding setting for your connector to UTF-8. See http://tomcat.apache.org/tomcat-5.5-doc/config/http.html.

2. As BalusC suggests, decode the query string yourself, and manually parse it (as opposed to using the ServletRequest APIs) into a parameter map yourself.

Hope this helps!

From the HttpServletRequest#getQueryString() javadoc:

Returns: a String containing the query string or null if the URL contains no query string. The value is not decoded by the container.

Note the last statement. So you need to URL-decode it youself using java.net.URLDecoder.

String queryString = URLDecoder.decode(request.getQueryString(), "UTF-8");

However, the normal way to gather parameters is just using HttpServletRequest#getParameter().

String param = request.getParameter("param"); // così

The servletcontainer has already URL-decoded it for you then if you have configured it to use the correct encoding. The request.setCharacterEncoding() has only effect on the request body (POST) not on the request URI (GET). Also see Mirage's answer.