Quickest way to get content type

Question

I need to chech for the content type (if it\'s image, audio or video) of an url which has been inserted by the user. I have a code like this:

URL url = new U         


        

Answer 1

If the "other" end supports it, could you use the HEAD HTTP method?

Answer 2

Thanks to DaveHowes answer and googling around about how to get HEAD I got it in this way:

URL url = new URL(urlname);
HttpURLConnection connection = (HttpURLConnection)  url.openConnection();
connection.setRequestMethod("HEAD");
connection.connect();
String contentType = connection.getContentType();

Answer 3

Be aware of redirects, I faced same problem with my remote content check.
Here is my fix:

/**
 * Http HEAD Method to get URL content type
 *
 * @param urlString
 * @return content type
 * @throws IOException
 */
public static String getContentType(String urlString) throws IOException{
    URL url = new URL(urlString);
    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
    connection.setRequestMethod("HEAD");
    if (isRedirect(connection.getResponseCode())) {
        String newUrl = connection.getHeaderField("Location"); // get redirect url from "location" header field
        logger.warn("Original request URL: '{}' redirected to: '{}'", urlString, newUrl);
        return getContentType(newUrl);
    }
    String contentType = connection.getContentType();
    return contentType;
}

/**
 * Check status code for redirects
 * 
 * @param statusCode
 * @return true if matched redirect group
 */
protected static boolean isRedirect(int statusCode) {
    if (statusCode != HttpURLConnection.HTTP_OK) {
        if (statusCode == HttpURLConnection.HTTP_MOVED_TEMP
            || statusCode == HttpURLConnection.HTTP_MOVED_PERM
                || statusCode == HttpURLConnection.HTTP_SEE_OTHER) {
            return true;
        }
    }
    return false;
}

You could also put some counter for maxRedirectCount to avoid infinite redirects loop - but this is not covered here. This is just a inspiration.