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006// *                                                                                                                         *
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012// ***************************************************************************************************************************
013package org.apache.juneau.http;
014
015/**
016 * Represents a parsed <l>User-Agent</l> HTTP request header.
017 * 
018 * <p>
019 * The user agent string of the user agent.
020 * 
021 * <h5 class='figure'>Example</h5>
022 * <p class='bcode'>
023 *    User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20100101 Firefox/21.0
024 * </p>
025 * 
026 * <h5 class='topic'>RFC2616 Specification</h5>
027 * 
028 * The User-Agent request-header field contains information about the user agent originating the request.
029 * This is for statistical purposes, the tracing of protocol violations, and automated recognition of user agents for
030 * the sake of tailoring responses to avoid particular user agent limitations.
031 * User agents SHOULD include this field with requests.
032 * The field can contain multiple product tokens (section 3.8) and comments identifying the agent and any sub-products
033 * which form a significant part of the user agent.
034 * By convention, the product tokens are listed in order of their significance for identifying the application.
035 * 
036 * <p class='bcode'>
037 *    User-Agent     = "User-Agent" ":" 1*( product | comment )
038 * </p>
039 * 
040 * <p>
041 * Example:
042 * <p class='bcode'>
043 *    User-Agent: CERN-LineMode/2.15 libwww/2.17b3
044 * </p>
045 * 
046 * <h5 class='section'>See Also:</h5>
047 * <ul class='doctree'>
048 *    <li class='extlink'><a class='doclink' href='https://www.w3.org/Protocols/rfc2616/rfc2616.html'>Hypertext Transfer Protocol -- HTTP/1.1</a>
049 * </ul>
050 */
051public final class UserAgent extends HeaderString {
052
053   /**
054    * Returns a parsed <code>User-Agent</code> header.
055    * 
056    * @param value The <code>User-Agent</code> header string.
057    * @return The parsed <code>User-Agent</code> header, or <jk>null</jk> if the string was null.
058    */
059   public static UserAgent forString(String value) {
060      if (value == null)
061         return null;
062      return new UserAgent(value);
063   }
064
065   private UserAgent(String value) {
066      super(value);
067   }
068}