Java 获取域名服务器地址

已测验

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.Map;

/**
 * Created by denghb on 2016/12/6.
 */
public class AppTest {

    public static void main(String[] args) {
        System.out.println(getHostIP("www.sina.com.cn"));
    }

    /**
     * 获取单个ip
     *
     * @param domain
     * @return
     */
    public static String getHostIP(final String domain) {
        return getHostIPs(domain)[0];
    }

    /**
     * 清理缓存
     *
     * @param domain
     * @return
     */
    public static void clearIPCache(final String domain) {

        try {
            // 清除缓存数据
            Class inetAddressClass = java.net.InetAddress.class;
            final java.lang.reflect.Field cacheField = inetAddressClass.getDeclaredField("addressCache");
            cacheField.setAccessible(true);

            final Object obj = cacheField.get(inetAddressClass);
            Class cacheClazz = obj.getClass();
            final java.lang.reflect.Field cachePolicyField = cacheClazz.getDeclaredField("policy");
            final java.lang.reflect.Field cacheMapField = cacheClazz.getDeclaredField("cache");
            cachePolicyField.setAccessible(true);
            cacheMapField.setAccessible(true);
            final Map cacheMap = (Map) cacheMapField.get(obj);
            cacheMap.remove(domain);

        } catch (IllegalAccessException e) {
            // TODO
        } catch (NoSuchFieldException e) {
            // TODO
        }
    }

    /**
     * 获取所有ip
     *
     * @param domain
     * @return
     */
    public static String[] getHostIPs(final String domain) {
        // 清理缓存
        clearIPCache(domain);

        String ips[] = new String[1];

        try {
            // 获取IP地址
            InetAddress[] addrs = InetAddress.getAllByName(domain);
            if (null != addrs) {
                int len = addrs.length;
                ips = new String[len];
                for (int i = 0; i < len; i++) {
                    ips[i] = addrs[i].getHostAddress();
                }
            }
        } catch (UnknownHostException e) {
            // TODO
        }
        return ips;
    }
}

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