Parsing query strings on Android

Question

On Android:

import android.net.Uri;

[...]

Uri uri=Uri.parse(url_string);
uri.getQueryParameter("para1");

Since Android M things have got more complicated. The answer of android.net.URI.getQueryParameter() has a bug which breaks spaces before JellyBean. Apache URLEncodedUtils.parse() worked, but was deprecated in L, and removed in M.

So the best answer now is UrlQuerySanitizer. This has existed since API level 1 and still exists. It also makes you think about the tricky issues like how do you handle special characters, or repeated values.

The simplest code is

UrlQuerySanitizer.ValueSanitizer sanitizer = UrlQuerySanitizer.getAllButNullLegal();
// remember to decide if you want the first or last parameter with the same name
// If you want the first call setPreferFirstRepeatedParameter(true);
sanitizer.parseUrl(url);
String value = sanitizer.getValue("paramName");

If you are happy with the default parsing behavior you can do:

new UrlQuerySanitizer(url).getValue("paramName")

but you should make sure you understand what the default parsing behavor is, as it might not be what you want.

On Android, the Apache libraries provide a Query parser:

http://developer.android.com/reference/org/apache/http/client/utils/URLEncodedUtils.html and http://hc.apache.org/httpcomponents-client-ga/httpclient/apidocs/org/apache/http/client/utils/URLEncodedUtils.html

public static Map<String, List<String>> getUrlParameters(String url)
        throws UnsupportedEncodingException {
    Map<String, List<String>> params = new HashMap<String, List<String>>();
    String[] urlParts = url.split("\\?");
    if (urlParts.length > 1) {
        String query = urlParts[1];
        for (String param : query.split("&")) {
            String pair[] = param.split("=", 2);
            String key = URLDecoder.decode(pair[0], "UTF-8");
            String value = "";
            if (pair.length > 1) {
                value = URLDecoder.decode(pair[1], "UTF-8");
            }
            List<String> values = params.get(key);
            if (values == null) {
                values = new ArrayList<String>();
                params.put(key, values);
            }
            values.add(value);
        }
    }
    return params;
}