Name: dfR10049 Date: 05/29/2000




Javadoc states that java.net.InetAddress.getHostName() "Gets the host name
for this IP address". But the output of this method may be different for
the equal addresses. It depends of the way of the creating the InetAddress
object.

For example:

InetAddress of host: helmet.sparc.spb.su/192.168.205.166
The next three InetAddress objects will be equal:

  InetAddress i1 = InetAddress.getByName("helmet");
  InetAddress i2 = InetAddress.getByName("helmet.sparc.spb.su");
  InetAddress i3 = InetAddress.getByName("192.168.205.166");


But outputs of:
  System.out.println(i1.getHostName());
  System.out.println(i2.getHostName());
  System.out.println(i3.getHostName());

will be different:

helmet
helmet.sparc.spb.su
helmet


If InetAddress object has been created with getByName method with IP address
name parameter then result of getHostName() may be either fully qualified
domain name or not.

The reason of the ambiguity is impossibility to get FQDN from JDK.
There is a bug #4069806 (Synopsis: InetAddress contains unqualified host
names when running under NIS+) but it has been closed as will not fix.

So there is no good way to get FQDN from JDK now. This makes invalid
the next JCK-13 tests:

api/java_net/InetAddress/descriptions.html#ToString
api/java_net/InetAddress/descriptions.html#GetHostAddress

This bug should be fixed sooner or later or spec should be corrected to
be more clear about getHostName() method.


This is the test demonstrated the bug:

-------------------------------------
import java.net.*;
import java.io.*;


public class Test {

    public static void main (String args[]){
     
        try {
   
            InetAddress[] addr = new InetAddress[args.length];
            String[] host = new String[args.length];

            for (int i = 0; i < args.length; i++) {
                addr[i] = InetAddress.getByName(args[i]);
                host[i] = addr[i].getHostName();
                System.out.println("name: " + args[i]);
                System.out.println("hostName: " + addr[i].getHostName());
                System.out.println("----------------------------------");
            }

            boolean addrEqual = true;
            for (int i = 1; i < args.length; i++) {
                if (!addr[i].equals(addr[i-1]))
                    addrEqual = false;
            }

            boolean hostEqual = true;
            for (int i = 1; i < args.length; i++) {
                if (!host[i].equals(host[i-1]))
                    hostEqual = false;
            }
            
            if (addrEqual == hostEqual)
                System.out.println("Test passed");
            else
                System.out.println("Test failed");

        } catch (Exception e) {
            System.out.println(" " + e);
        }
    }
}

-------- output from the text ----------------
#helmet> java Test helmet helmet.sparc.spb.su 192.168.205.166
name: helmet
hostName: helmet
----------------------------------
name: helmet.sparc.spb.su
hostName: helmet.sparc.spb.su
----------------------------------
name: 192.168.205.166
hostName: helmet
----------------------------------
Test failed
#helmet>
----------------------------------------------

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