Java servlet and UTF-8 problem

Question

I have some problem with UTF-8. My client (realized in GWT) make a request to my servlet, with some parametres in the URL, as follow:

http://localhost:8080/servlet?param=value

When in the servlet I retrieve the URL, I have some problem with UTF-8 characters. I use this code:

protected void service(HttpServletRequest request, HttpServletResponse response) 
                    throws ServletException, IOException {

        request.setCharacterEncoding("UTF-8");

        String reqUrl = request.getRequestURL().toString(); 
        String queryString = request.getQueryString();
        System.out.println("Request: "+reqUrl + "?" + queryString);
        ...

So, if I call this url:

http://localhost:8080/servlet?param=così

the result is like this:

Request: http://localhost:8080/servlet?param=cos%C3%AC

What can I do to set up properly the character encoding?

Answer 1

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.

Answer 2

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!