Question

My application processes URLs entered manually by users. I have discovered that some of malformed URLs (like ‘http:/not-valid’) result in NullPointerException thrown when connection is being opened. As I learned from this Java bug report, the issue is known and will not be fixed. The suggestion is to use java.net.URI, which is "more RFC 2396-conformant".

Question is: how to use URI to work around the problem? The only thing I can do with URI is to use it to parse string and generate URL. I have prepared following program:

import java.net.*;

public class Test
{
    public static void main(String[] args)
    {
       try {
           URI uri = URI.create(args[0]);
           Object o = uri.toURL().getContent(); // try to get content
       }
       catch(Throwable e) {
           e.printStackTrace();
       }
    }
}

Here are results of my tests (with java 1.6.0_20), not much different from what I get with java.net.URL:

sh-3.2$ java Test url-not-valid
java.lang.IllegalArgumentException: URI is not absolute
        at java.net.URI.toURL(URI.java:1080)
        at Test.main(Test.java:9)
sh-3.2$ java Test http:/url-not-valid
java.lang.NullPointerException
        at sun.net.www.ParseUtil.toURI(ParseUtil.java:261)
        at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:795)
        at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:726)
        at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1049)
        at java.net.URLConnection.getContent(URLConnection.java:688)
        at java.net.URL.getContent(URL.java:1024)
        at Test.main(Test.java:9)
sh-3.2$ java Test http:///url-not-valid
java.lang.IllegalArgumentException: protocol = http host = null
        at sun.net.spi.DefaultProxySelector.select(DefaultProxySelector.java:151)
        at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:796)
        at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:726)
        at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1049)
        at java.net.URLConnection.getContent(URLConnection.java:688)
        at java.net.URL.getContent(URL.java:1024)
        at Test.main(Test.java:9)
sh-3.2$ java Test http:////url-not-valid
java.lang.NullPointerException
        at sun.net.www.ParseUtil.toURI(ParseUtil.java:261)
        at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:795)
        at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:726)
        at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1049)
        at java.net.URLConnection.getContent(URLConnection.java:688)
        at java.net.URL.getContent(URL.java:1024)
        at Test.main(Test.java:9)

Answer 1

You can use appache Validator Commons ..

UrlValidator urlValidator = new UrlValidator();
urlValidator.isValid("http://google.com");

http://commons.apache.org/validator/

http://commons.apache.org/validator/api-1.3.1/