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012// ***************************************************************************************************************************
013package org.apache.juneau.rest;
014
015import org.apache.juneau.rest.annotation.*;
016
017/**
018 * Class used for defining method-level matchers using the {@link RestMethod#matchers() @RestMethod.matchers()} annotation.
019 * 
020 * <p>
021 * Matchers are used to allow multiple Java methods to handle requests assigned to the same URL path pattern, but
022 * differing based on some request attribute, such as a specific header value.
023 * For example, matchers can be used to provide two different methods for handling requests from two different client
024 * versions.
025 * 
026 * <p>
027 * Java methods with matchers associated with them are always attempted before Java methods without matchers.
028 * This allows a 'default' method to be defined to handle requests where no matchers match.
029 * 
030 * <p>
031 * When multiple matchers are specified on a method, only one matcher is required to match.
032 * This is opposite from the {@link RestMethod#guards() @RestMethod.guards()} annotation, where all guards are required to match in order to
033 * execute the method.
034 * 
035 * <h5 class='section'>Example:</h5>
036 * <p class='bcode'>
037 *    <jk>public class</jk> MyResource <jk>extends</jk> RestServlet {
038 * 
039 *       <ja>@RestMethod</ja>(name=<jsf>GET</jsf>, path=<js>"/foo"</js>, matchers=IsDNT.<jk>class</jk>)
040 *       <jk>public</jk> Object doGetWithDNT() {
041 *          <jc>// Handle request with Do-Not-Track specified</jc>
042 *       }
043 * 
044 *       <ja>@RestMethod</ja>(name=<jsf>GET</jsf>, path=<js>"/foo"</js>)
045 *       <jk>public</jk> Object doGetWithoutDNT() {
046 *          <jc>// Handle request without Do-Not-Track specified</jc>
047 *       }
048 *    }
049 * 
050 *    <jk>public class</jk> IsDNT <jk>extends</jk> RestMatcher {
051 *       <ja>@Override</ja>
052 *       <jk>public boolean</jk> matches(RestRequest req) {
053 *          <jk>return</jk> req.getHeader(<jk>int</jk>.<jk>class</jk>, <js>"DNT"</js>, 0) == 1;
054 *       }
055 *    }
056 * </p>
057 * 
058 * <p>
059 * Instances must provide one of the following public constructors:
060 * <ul>
061 *    <li>No-args.
062 *    <li>The following args: <code>Object resource, Method javaMethod</code>.
063 *       <br>This gives access to the servlet/resource and Java method it's applied to.
064 * </ul>
065 * 
066 * <h5 class='section'>See Also:</h5>
067 * <ul>
068 *    <li class='link'><a class="doclink" href="../../../../overview-summary.html#juneau-rest-server.RestMethodMatchers">Overview &gt; juneau-rest-server &gt; @RestMethod.matchers()</a>
069 * </ul>
070 */
071public abstract class RestMatcher {
072
073   /**
074    * Returns <jk>true</jk> if the specified request matches this matcher.
075    * 
076    * @param req The servlet request.
077    * @return <jk>true</jk> if the specified request matches this matcher.
078    */
079   public abstract boolean matches(RestRequest req);
080
081   /**
082    * Returns <jk>true</jk> if this matcher is required to match in order for the method to be invoked.
083    * 
084    * <p>
085    * If <jk>false</jk>, then only one of the matchers must match.
086    * 
087    * @return <jk>true</jk> if this matcher is required to match in order for the method to be invoked.
088    */
089   public boolean mustMatch() {
090      return false;
091   }
092}