How to check for a valid URL in Java?

Question

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!.

Answer 1

validator package:

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 approach - check the network address

Sun's Java site offers connect attempt as a solution for validating URLs.

Other regex code snippets:

There are regex validation attempts at Oracle's site and weberdev.com.

Answer 2

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.

Answer 3

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.