자바 JNDI 자체 지정 DNS 서버 분석 도 메 인 IP

       /**
       * 获取DNS服务器信息
       *
       * @param domain  要获取DNS信息的域名
       * @param provider      DNS服务器
       * @param types   信息类型 "A"(IP信息)，"MX"
       * @param timeout 请求超时
       * @param retryCount    重试次数
       *
       * @return 所有信息组成的数组
       *
       * @throws NamingException
       *        
       */

       @SuppressWarnings("rawtypes" )
       public static ArrayList<String> getDNSRecs(String domain, String provider,
                  String [] types, int timeout, int retryCount) throws NamingException {
            
            ArrayList<String> results = new ArrayList<String>(15);
            
            Hashtable<String, String> env = new Hashtable<String, String>();
            
            env.put( "java.naming.factory.initial" ,
                         "com.sun.jndi.dns.DnsContextFactory" );
            
             //设置域名服务器
            env.put(Context. PROVIDER_URL, "dns://" + provider);
            
             // 连接时间
            env.put( "com.sun.jndi.dns.timeout.initial" , String.valueOf(timeout));
            
             // 连接次数
            env.put( "com.sun.jndi.dns.timeout.retries" , String.valueOf(retryCount));
            
            DirContext ictx = new InitialDirContext(env);
            Attributes attrs = ictx.getAttributes(domain, types);
            
             for (Enumeration e = attrs.getAll(); e.hasMoreElements();) {
                  Attribute a = (Attribute) e.nextElement();
                   int size = a.size();
                   for (int i = 0; i < size; i++) {
                        results.add((String) a.get(i));
                  }
            }
             return results;
      }

       /**
       * 获取域名所有IP
       * @param domain  域名
       * @param dnsServers    DNS服务器列表
       * @param timeout 请求超时
       * @param retryCount    重试次数
       * @return
       */
       public static Set<String> getAllIP(String domain, String[] dnsServers,
                   int timeout, int retryCount) {
            Set<String> ips = new HashSet<String>();
            
             for(String dnsServer: dnsServers) {
                  List<String> ipList;
                   try {
                        ipList = getDNSRecs(domain, dnsServer, new String[]{"A"},
                                    timeout, retryCount);
                  } catch (NamingException e) {
                         continue;
                  }
                  ips.addAll(ipList);
            }
            
             return ips;
      }