content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package org.apache.ambari.server.utils;
  
  import java.util.regex.Pattern;
  
  /**
   * HostUtils provides utilities related to processing and validating hosts and host names.
   */
  public class HostUtils {
    /**
     * A regular expression to validate that a hostname meets the specifications described in RFC 1123.
     * <p>
     * Various sources on the Internet specific this regular expression for hostname validation.
     */
    private static final Pattern REGEX_VALID_HOSTNAME = Pattern.compile("^(?:(?:[a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\\-]*[a-zA-Z0-9])\\.)*(?:[A-Za-z0-9]|[A-Za-z0-9][A-Za-z0-9\\-]*[A-Za-z0-9])$");
  
    /**
     * Validates a hostname to ensure it meets the specifications described in RFC 1123.
     * <p>
     * Note: this does not validate whether the host exists or if the name is a valid DNS name.
     * For example,  host.example.anything is a valid host name however may be an invalid DNS name
     * since "anything" may not be a valid top-level domain.
     *
     * @param hostname a hostname
     * @return true if the hostname is valid; false otherwise
     */
    public static boolean isValidHostname(String hostname) {
      return (hostname != null) && REGEX_VALID_HOSTNAME.matcher(hostname).matches();
    }
  }
  