private static Object getAddressFromNameService(String host, InetAddress reqAddr)
throws UnknownHostException {
Object obj = null;
boolean success = false;
UnknownHostException ex = null;
// Check whether the host is in the lookupTable.
// 1) If the host isn't in the lookupTable when
// checkLookupTable() is called, checkLookupTable()
// would add the host in the lookupTable and
// return null. So we will do the lookup.
// 2) If the host is in the lookupTable when
// checkLookupTable() is called, the current thread
// would be blocked until the host is removed
// from the lookupTable. Then this thread
// should try to look up the addressCache.
// i) if it found the address in the
// addressCache, checkLookupTable() would
// return the address.
// ii) if it didn't find the address in the
// addressCache for any reason,
// it should add the host in the
// lookupTable and return null so the
// following code would do a lookup itself.
if ((obj = checkLookupTable(host)) == null) {
// This is the first thread which looks up the address
// this host or the cache entry for this host has been
// expired so this thread should do the lookup.
for (NameService nameService : nameServices) {
try {
/*
* Do not put the call to lookup() inside the
* constructor. if you do you will still be
* allocating space when the lookup fails.
*/
obj = nameService.lookupAllHostAddr(host);
success = true;
break;
} catch (UnknownHostException uhe) {
if (host.equalsIgnoreCase("localhost")) {
InetAddress[] local = new InetAddress[] {impl.loopbackAddress()};
obj = local;
success = true;
break;
} else {
obj = unknown_array;
success = false;
ex = uhe;
}
}
}
// More to do?
InetAddress[] addrs = (InetAddress[]) obj;
if (reqAddr != null && addrs.length > 1 && !addrs[0].equals(reqAddr)) {
// Find it?
int i = 1;
for (; i < addrs.length; i++) {
if (addrs[i].equals(reqAddr)) {
break;
}
}
// Rotate
if (i < addrs.length) {
InetAddress tmp, tmp2 = reqAddr;
for (int j = 0; j < i; j++) {
tmp = addrs[j];
addrs[j] = tmp2;
tmp2 = tmp;
}
addrs[i] = tmp2;
}
}
// Cache the address.
cacheAddress(host, obj, success);
// Delete the host from the lookupTable, and
// notify all threads waiting for the monitor
// for lookupTable.
updateLookupTable(host);
if (!success && ex != null) throw ex;
}
return obj;
}
