org.josef.util

Class DnsUtil

java.lang.Object

org.josef.util.DnsUtil

public final class DnsUtil
extends Object

DNS related utility class.
This class uses Sun's com.sun.jndi.dns.DnsContextFactory which may not be present at run-time.

Version:

1.0 $Revision: 6444 $

Author:

Kees Schotanus.

Method Summary

Modifier and Type	Method and Description
static List<Attribute>	getAllAttributes(String hostName) Gets all attributes of the supplied hostName.
static Attribute	getAttribute(String hostName, String attributeName) Gets a single attribute from the supplied hostName.
static List<MailServer>	getMailServers(String hostName) Gets the mail servers of the supplied hostName.
static com.sun.jndi.dns.DnsContext	lookup(String hostName) Performs a lookup of the supplied hostName.
static void	main(String[] args) For demonstration purposes only.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

lookup

public static com.sun.jndi.dns.DnsContext lookup(String hostName)
                                          throws NamingException

Performs a lookup of the supplied hostName.

Parameters:

hostName - Host name to lookup.

Returns:

The DNS context.

Throws:

NamingException - When the supplied hostName could not be looked up.

getMailServers

public static List<MailServer> getMailServers(String hostName)
                                       throws NamingException

Gets the mail servers of the supplied hostName.

Parameters:

hostName - Host name.

Returns:

A list of mail servers ordered by preference from the lowest preference number to the highest.
Confusingly, the lower the integer preference number, the higher the mail server's preference.
The returned list may be empty but will never be null.

Throws:

NamingException - When the supplied hostName could not be looked up.

getAttribute

public static Attribute getAttribute(String hostName,
                                     String attributeName)
                              throws NamingException

Gets a single attribute from the supplied hostName.
Supplying "MX" for example would return the Mail eXchange attribute.

Parameters:

hostName - Host name.

attributeName - Name of the attribute to get.

Returns:

The attribute with the supplied attributeName or null when no such attribute exists.

Throws:

NamingException - When the attribute could not be looked up.
This happens for example when an illegal hostName has been supplied.

getAllAttributes

public static List<Attribute> getAllAttributes(String hostName)
                                        throws NamingException

Gets all attributes of the supplied hostName.

Parameters:

hostName - Host name.

Returns:

A list of all attributes of the supplied hostName.
The returned list may be empty but will never be null.

Throws:

NamingException - When the supplied hostName could not be looked up.

main

public static void main(String[] args)
                 throws NamingException

For demonstration purposes only.

Parameters:

args - Not used.

Throws:

NamingException - When a DNS lookup error occurs.