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Submit an HTML form using POST method via Java

In the recent days I'm studying how to implement HTTP/REST architecture in Java.
I decided to work without any REST framework, so nothing like Jersey or restlet. Instead I decided to exploit the good old Servlet API which seems to use an faithful model on how the HTTP works.

And also I decided to starts from study how to design Web applications in a way that uses correctly the HTTP protocol.

During my study I didn't find a HTTP client which fit my requirements so I'm writing some client functionalities from scratch. This is the way I implemented the posting of a form with only one parameter:

private static InputStream postForm(final String url,
        final String paramName,
        final String paramValue) throws IOException
{
    return new Object() {

        public InputStream postForm() throws IOException {
            prepareConnectionToServer();
            packageFormValuesInAMessage();
            submitTheMessage();
            return theServerReply();
        }

        private void prepareConnectionToServer() throws IOException {
            connection = new URL(url).openConnection();
            connection.setDoInput(true);
            connection.setDoOutput(true);
            connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
        }

        private URLConnection connection;

        private void packageFormValuesInAMessage() throws UnsupportedEncodingException {
            message = String.format("%s=%s", paramName, URLEncoder.encode(paramValue, "UTF-8"));
        }

        private String message;

        private void submitTheMessage() throws IOException {
            OutputStream output = connection.getOutputStream();
            output.write(message.getBytes("UTF-8"));
            output.close();
        }

        private InputStream theServerReply() throws IOException {
            return connection.getInputStream();
        }

    }.postForm();
}