Java UnknownHostException.initCause方法代碼示例

import java.net.UnknownHostException; //導入方法依賴的package包/類
@Override public List<InetAddress> lookup(String hostname) throws UnknownHostException {
  if (hostname == null) throw new UnknownHostException("hostname == null");
  try {
    return Arrays.asList(InetAddress.getAllByName(hostname));
  } catch (NullPointerException e) {
    UnknownHostException unknownHostException =
        new UnknownHostException("Broken system behaviour for dns lookup of " + hostname);
    unknownHostException.initCause(e);
    throw unknownHostException;
  }
}
 

import java.net.UnknownHostException; //導入方法依賴的package包/類
/**
 * Returns an <code>InetAddress</code> object encapsulating what is most likely the machine's LAN IP address.
 * <p/>
 * This method is intended for use as a replacement of JDK method <code>InetAddress.getLocalHost</code>, because
 * that method is ambiguous on Linux systems. Linux systems enumerate the loopback network interface the same
 * way as regular LAN network interfaces, but the JDK <code>InetAddress.getLocalHost</code> method does not
 * specify the algorithm used to select the address returned under such circumstances, and will often return the
 * loopback address, which is not valid for network communication. Details
 * <a href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4665037">here</a>.
 * <p/>
 * This method will scan all IP addresses on all network interfaces on the host machine to determine the IP address
 * most likely to be the machine's LAN address. If the machine has multiple IP addresses, this method will prefer
 * a site-local IP address (e.g. 192.168.x.x or 10.10.x.x, usually IPv4) if the machine has one (and will return the
 * first site-local address if the machine has more than one), but if the machine does not hold a site-local
 * address, this method will return simply the first non-loopback address found (IPv4 or IPv6).
 * <p/>
 * If this method cannot find a non-loopback address using this selection algorithm, it will fall back to
 * calling and returning the result of JDK method <code>InetAddress.getLocalHost</code>.
 * <p/>
 *
 * @throws UnknownHostException If the LAN address of the machine cannot be found.
 *
 * Thanks to https://issues.apache.org/jira/browse/JCS-40 for this code
 */
private static InetAddress getLocalHostLANAddress() throws UnknownHostException {
    try {
        InetAddress candidateAddress = null;
        // Iterate all NICs (network interface cards)...
        for (Enumeration<NetworkInterface> ifaces = NetworkInterface.getNetworkInterfaces(); ifaces.hasMoreElements();) {
            NetworkInterface iface = (NetworkInterface) ifaces.nextElement();
            // Iterate all IP addresses assigned to each card...
            for (Enumeration<InetAddress> inetAddrs = iface.getInetAddresses(); inetAddrs.hasMoreElements();) {
                InetAddress inetAddr = (InetAddress) inetAddrs.nextElement();
                if (!inetAddr.isLoopbackAddress()) {

                    if (inetAddr.isSiteLocalAddress()) {
                        // Found non-loopback site-local address. Return it immediately...
                        return inetAddr;
                    }
                    else if (candidateAddress == null) {
                        // Found non-loopback address, but not necessarily site-local.
                        // Store it as a candidate to be returned if site-local address is not subsequently found...
                        candidateAddress = inetAddr;
                        // Note that we don't repeatedly assign non-loopback non-site-local addresses as candidates,
                        // only the first. For subsequent iterations, candidate will be non-null.
                    }
                }
            }
        }
        if (candidateAddress != null) {
            // We did not find a site-local address, but we found some other non-loopback address.
            // Server might have a non-site-local address assigned to its NIC (or it might be running
            // IPv6 which deprecates the "site-local" concept).
            // Return this non-loopback candidate address...
            return candidateAddress;
        }
        // At this point, we did not find a non-loopback address.
        // Fall back to returning whatever InetAddress.getLocalHost() returns...
        InetAddress jdkSuppliedAddress = InetAddress.getLocalHost();
        if (jdkSuppliedAddress == null) {
            throw new UnknownHostException("The JDK InetAddress.getLocalHost() method unexpectedly returned null.");
        }
        return jdkSuppliedAddress;
    }
    catch (Exception e) {
        UnknownHostException unknownHostException = new UnknownHostException("Failed to determine LAN address: " + e);
        unknownHostException.initCause(e);
        throw unknownHostException;
    }
}
 

import java.net.UnknownHostException; //導入方法依賴的package包/類
/**
 * Returns an <code>InetAddress</code> object encapsulating what is most likely the machine's LAN IP address.
 * <p/>
 * This method is intended for use as a replacement of JDK method <code>InetAddress.getLocalHost</code>, because that method is ambiguous on Linux systems. Linux systems enumerate the loopback network interface the same way as regular LAN network
 * interfaces, but the JDK <code>InetAddress.getLocalHost</code> method does not specify the algorithm used to select the address returned under such circumstances, and will often return the loopback address, which is not valid for network
 * communication. Details <a href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4665037">here</a>.
 * <p/>
 * This method will scan all IP addresses on all network interfaces on the host machine to determine the IP address most likely to be the machine's LAN address. If the machine has multiple IP addresses, this method will prefer a site-local IP
 * address (e.g. 192.168.x.x or 10.10.x.x, usually IPv4) if the machine has one (and will return the first site-local address if the machine has more than one), but if the machine does not hold a site-local address, this method will return simply
 * the first non-loopback address found (IPv4 or IPv6).
 * <p/>
 * If this method cannot find a non-loopback address using this selection algorithm, it will fall back to calling and returning the result of JDK method <code>InetAddress.getLocalHost</code>.
 * <p/>
 *
 * @throws UnknownHostException
 *             If the LAN address of the machine cannot be found.
 */
public static InetAddress search() throws UnknownHostException {
	try {
		InetAddress candidateAddress = null;
		// Iterate all NICs (network interface cards)...
		for (Enumeration<NetworkInterface> ifaces = NetworkInterface.getNetworkInterfaces(); ifaces.hasMoreElements();) {
			NetworkInterface iface = ifaces.nextElement();
			AitLogger.trace(logger, "Analizando interfaz de red: {}", iface.getName());
			// Iterate all IP addresses assigned to each card...
			for (Enumeration<InetAddress> inetAddrs = iface.getInetAddresses(); inetAddrs.hasMoreElements();) {
				InetAddress inetAddr = inetAddrs.nextElement();
				AitLogger.trace(logger, "InetAddr {}: loopback: {}", inetAddr.getHostAddress(), inetAddr.isLoopbackAddress());
				if (!inetAddr.isLoopbackAddress()) {
					AitLogger.trace(logger, "InetAddr {}: siteLocal: {}", inetAddr.getHostAddress(), inetAddr.isSiteLocalAddress());
					if (inetAddr.isSiteLocalAddress()) {
						// Found non-loopback site-local address. Return it immediately...
						return inetAddr;
					} else if (candidateAddress == null) {
						// Found non-loopback address, but not necessarily site-local.
						// Store it as a candidate to be returned if site-local address is not subsequently found...
						candidateAddress = inetAddr;
						// Note that we don't repeatedly assign non-loopback non-site-local addresses as candidates,
						// only the first. For subsequent iterations, candidate will be non-null.
					}
				}
			}
		}
		if (candidateAddress != null) {
			// We did not find a site-local address, but we found some other non-loopback address.
			// Server might have a non-site-local address assigned to its NIC (or it might be running
			// IPv6 which deprecates the "site-local" concept).
			// Return this non-loopback candidate address...
			return candidateAddress;
		}
		// At this point, we did not find a non-loopback address.
		// Fall back to returning whatever InetAddress.getLocalHost() returns...
		InetAddress jdkSuppliedAddress = InetAddress.getLocalHost();
		AitLogger.trace(logger, "Sin candidatos, retornando metodo normal: {}", jdkSuppliedAddress);
		if (jdkSuppliedAddress == null) {
			throw new UnknownHostException("The JDK InetAddress.getLocalHost() method unexpectedly returned null.");
		}
		return jdkSuppliedAddress;
	} catch (Exception e) {
		UnknownHostException unknownHostException = new UnknownHostException("Failed to determine LAN address: " + e);
		unknownHostException.initCause(e);
		throw unknownHostException;
	}
}