Problem extracting port number with URL.getPort() when URL contains "]"

Question

I'm using java.net.URL.getPort() to extract the port number from a URL. Most of the time this works great. However, when the URL contains a right bracket character "]" it fails:

new URL("http://abc.com:123/abc.mp3").getPort();
 returns: (int) 123

But if the URL contains "]" I get:

new URL("http://abc.com:123/abc].mp3").getPort();
 returns: (int) -1

What am I doing wrong?

EDIT #1: As a test, I pasted this same code into a non-Android Java app and the port number was correctly returned, so this appears to be an anomaly with the Android SDK.

Answer 1

If your URL contains some symbols that are not valid in URLs, you have to use an URL-encoded String. They way to do it in Java seem to be by using URI.

new URI( "http", null, "abc.com", 123, "abc].mp3", null, null).toURL().getPort();

If you already has an URL string:

URL url = new URL("http://abc.com:123/abc].mp3");

Then this works for me:

new URI(
    url.getProtocol(),
    null,
    url.getHost(),
    url.getPort(),
    url.getPath(),
    null,
    null);

But then again I'm using url.getPort() that you said didn't work. But when I'm testing on Java 6 now. new URL("http://abc.com:123/abc].mp3").getPort(); actually works for me, maybe it's just on Android it doesn't work? In case it doesn't work I think it's best to use a third party library for this. Apache Http Client that is included in Android seem to have some extra functionality for URLs: see org.apache.http.client.utils

See also HTTP URL Address Encoding in Java

Answer 2

"http://abc.com:123/abc].mp3"

] is not allowed in the path part of a URI, so this is not a URL. However, you can modify the regular expression in the spec to get this information:

    //TODO: import java.util.regex.*;
    String expr = "^(([^:/?#]+):)?(//([^:/?#]*):([\\d]*))?";
    Matcher matcher = Pattern.compile(expr)
                             .matcher("http://abc.com:123/abc].mp3");
    if (matcher.find()) {
      String port = matcher.group(5);
      System.out.println(port);
    }

Despite the name, URLEncoder doesn't encode URLs. It should only be used to encode parameters in the query part when the server is expecting application/x-www-form-urlencoded encoded data. The URI and URL classes behave as documented - they aren't going to help you here.

Answer 3

Here is a simpler way to extract port from URLs that may be different from HTTP, e.g. JNDI connection URLs:

int port = 80; // assumption of default port in the URL
Pattern p = Pattern.compile(":\\d+"); // look for the first occurrence of colon followed by a number
Matcher matcher = p.matcher(urlSrtr);
if (matcher.find()) {
    String portStrWithColon = matcher.group();
    if (portStrWithColon.length() > 1) {
        String portStr = portStrWithColon.substring(1);
        try {
            port = Integer.parseInt(portStr);
        } catch (NumberFormatException e) {
            // handle
        }
    }
}
return port;

Answer 4

According to RFC1738 the ] character is unsafe:

Other characters are unsafe because gateways and other transport agents are known to sometimes modify such characters. These characters are "{", "}", "|", "\", "^", "~", "[", "]", and "`".

Thus, only alphanumerics, the special characters "$-_.+!*'(),", and reserved characters used for their reserved purposes may be used unencoded within a URL.

You should encode either the individual character that you want to add, or run the whole string through a URL encoder. Try this:

new URL("http://abc.com:123/abc%5D.mp3").getPort();

Answer 5

String encodedURL = new URI("http", null, "//abc.com:8080/abc[d].jpg", null, null).toASCIIString();