Using dnsjava to query using java?

Question

I am trying to query using the google public dns server (8.8.8.8) to get the IP address of some known URL. However, it seems like I am not able to get that using the following code? I am using the dnsjava java library. This is my current code

The results

        Lookup lookup = new Lookup("stackoverflow.com", Type.NS);
        SimpleResolver resolver=new SimpleResolver("8.8.8.8");

        lookup.setDefaultResolver(resolver);
        lookup.setResolver(resolver);
        Record [] records = lookup.run();
        for (int i = 0; i < records.length; i++) {
            Record  r = (Record ) records[i];
            System.out.println(r.getName()+","+r.getAdditionalName());
        }
    }
    catch (  Exception ex) {
        ex.printStackTrace();
        logger.error(ex.getMessage(),ex);
    }

Results:

stackoverflow.com.,ns-1033.awsdns-01.org.
stackoverflow.com.,ns-cloud-e1.googledomains.com.
stackoverflow.com.,ns-cloud-e2.googledomains.com.
stackoverflow.com.,ns-358.awsdns-44.com.

Answer 1

You don't need a DNS library just to look up an IP address. You can simply use JNDI :

Properties env = new Properties();
env.setProperty(Context.INITIAL_CONTEXT_FACTORY,
    "com.sun.jndi.dns.DnsContextFactory");
env.setProperty(Context.PROVIDER_URL, "dns://8.8.8.8");

DirContext context = new InitialDirContext(env);
Attributes list = context.getAttributes("stackoverflow.com",
    new String[] { "A" });

NamingEnumeration<? extends Attribute> records = list.getAll();
while (records.hasMore()) {
    Attribute record = records.next();
    String name = record.get().toString();
    System.out.println(name);
}

If you insist on using the dnsjava library, you need to use Type.A (as your code was originally doing, before your edit).

Looking at the documentation for the Record class , notice the long list under Direct Known Subclasses . You need to cast each Record to the appropriate subclass, which in this case is ARecord .

Once you've done that cast, you have an additional method available, getAddress :

for (int i = 0; i < records.length; i++) {
    ARecord r = (ARecord) records[i];
    System.out.println(r.getName() + "," + r.getAdditionalName()
        + " => " + r.getAddress());
}