springcloud注册hostname或者ip的那些事

EurekaInstanceConfigBean
/**
 * Flag to say that, when guessing a hostname, the IP address of the server should be
 * used in prference to the hostname reported by the OS.
 */
 private boolean preferIpAddress = false;

@Override
public String getHostName(boolean refresh) {
 if (refresh && !this.hostInfo.override) {
  this.ipAddress = this.hostInfo.getIpAddress();
  this.hostname = this.hostInfo.getHostname();
 }
 return this.preferIpAddress ? this.ipAddress : this.hostname;
}

public void setIpAddress(String ipAddress) {
 this.ipAddress = ipAddress;
 this.hostInfo.override = true;
 }

public EurekaInstanceConfigBean(InetUtils inetUtils) {
 this.inetUtils = inetUtils;
 this.hostInfo = this.inetUtils.findFirstNonLoopbackHostInfo();
 this.ipAddress = this.hostInfo.getIpAddress();
 this.hostname = this.hostInfo.getHostname();
}

public InetAddress findFirstNonLoopbackAddress() {
 InetAddress result = null;
 try {
  // 记录网卡最小索引
  int lowest = Integer.MAX_VALUE; 
  // 获取所有网卡
  for (Enumeration<NetworkInterface> nics = NetworkInterface
   .getNetworkInterfaces(); nics.hasMoreElements();) {
  NetworkInterface ifc = nics.nextElement();
  if (ifc.isUp()) {//判断网卡是否工作
   log.trace("Testing interface: " + ifc.getDisplayName());
   if (ifc.getIndex() < lowest || result == null) {
   lowest = ifc.getIndex();
   }
   else if (result != null) {
   continue;
   }
   // @formatter:off
   //网卡不忽略列表中
   if (!ignoreInterface(ifc.getDisplayName())) {
   for (Enumeration<InetAddress> addrs = ifc
    .getInetAddresses(); addrs.hasMoreElements();) {
    InetAddress address = addrs.nextElement();
    if (
 address instanceof Inet4Address//是IPV4
 && !address.isLoopbackAddress()//不是回环地址(127.***)
 && isPreferredAddress(address)) {//有推荐网卡,判断是推荐网卡内的ip
    log.trace("Found non-loopback interface: "
     + ifc.getDisplayName());
    result = address;
    }
   }
   }
   // @formatter:on
  }
  }
 }
 catch (IOException ex) {
  log.error("Cannot get first non-loopback address", ex);
 }
 if (result != null) {
  return result;
 }
 try {
  //都没有找到使用JDK的InetAddress获取
  return InetAddress.getLocalHost();
 }
 catch (UnknownHostException e) {
  log.warn("Unable to retrieve localhost");
 }
 return null;
}