What is the best way to check if a URL is valid in Java?
If tried to call new URL(urlString) and catch a MalformedURLException, but it seems to be happy with anything that begins with http://.
I'm not concerned about establishing a connection, just validity. Is there a method for this? An annotation in Hibernate Validator? Should I use a regex?
Edit: Some examples of accepted URLs are http://*** and http://my favorite site!.
Consider using the Apache Commons UrlValidator class
UrlValidator urlValidator = new UrlValidator();
urlValidator.isValid("http://my favorite site!");
There are several properties that you can set to control how this class behaves, by default http, https, and ftp are accepted.
My favorite approach, without external libraries:
try {
URI uri = new URI(name);
// perform checks for scheme, authority, host, etc., based on your requirements
if ("mailto".equals(uri.getScheme()) {/*Code*/}
if (uri.getHost() == null) {/*Code*/}
} catch (URISyntaxException e) {
}
The most "foolproof" way is to check for the availability of URL:
public boolean isURL(String url) {
try {
(new java.net.URL(url)).openStream().close();
return true;
} catch (Exception ex) { }
return false;
}
Judging by the source code for URI, the
public URL(URL context, String spec, URLStreamHandler handler)
constructor does more validation than the other constructors. You might try that one, but YMMV.
There seems to be a nice package by Yonatan Matalon called UrlUtil. Quoting its API:
isValidWebPageAddress(java.lang.String address, boolean validateSyntax,
boolean validateExistance)
Checks if the given address is a valid web page address.
Sun's Java site offers connect attempt as a solution for validating URLs.
There are regex validation attempts at Oracle's site and weberdev.com.