001// ***************************************************************************************************************************
002// * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements.  See the NOTICE file *
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006// *                                                                                                                         *
007// *  http://www.apache.org/licenses/LICENSE-2.0                                                                             *
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012// ***************************************************************************************************************************
013package org.apache.juneau.rest;
014
015import org.apache.juneau.rest.annotation.*;
016
017/**
018 * Class used to resolve {@link Class} objects to instances.
019 * 
020 * <p>
021 * Used to convert classes defined via {@link RestResource#children() @RestResource.children()} into child instances.
022 * 
023 * <p>
024 * Subclasses can be created to provide customized resource resolution.
025 * These can be associated with REST resources in one of the following ways:
026 * <ul>
027 *    <li>{@link RestResource#resourceResolver() @RestResource.resourceResolver()} annotation.
028 *    <li>{@link RestContextBuilder#resourceResolver(Class)}/{@link RestContextBuilder#resourceResolver(RestResourceResolver)}
029 *       methods.
030 * </ul>
031 * 
032 * Implementations must provide one of the following public constructors:
033 * <ul>
034 *    <li>RestResourceResolver()
035 *    <li>RestResourceResolver(RestContext)
036 * </ul>
037 * 
038 * <h5 class='section'>See Also:</h5>
039 * <ul>
040 *    <li class='link'><a class="doclink" href="../../../../overview-summary.html#juneau-rest-server.ResourceResolvers">Overview &gt; juneau-rest-server &gt; Resource Resolvers</a>
041 * </ul>
042 */
043public interface RestResourceResolver {
044
045   /**
046    * Represents no RestResourceResolver.
047    * 
048    * <p>
049    * Used on annotation to indicate that the value should be inherited from the parent class, and
050    * ultimately {@link BasicRestResourceResolver} if not specified at any level.
051    */
052   public interface Null extends RestResourceResolver {}
053   
054   /**
055    * Resolves the specified class to a resource object.
056    * 
057    * <p>
058    * Subclasses can override this method to provide their own custom resolution.
059    * 
060    * <p>
061    * The default implementation simply creates a new class instance using {@link Class#newInstance()}.
062    * 
063    * @param parent 
064    *    The parent resource (i.e. the instance whose class has the {@link RestResource#children() @RestResource.children()} annotation.
065    * @param c The class to resolve.
066    * @param builder The initialization configuration for the resource.
067    * @return The instance of that class.
068    * @throws Exception If class could not be resolved.
069    */
070   Object resolve(Object parent, Class<?> c, RestContextBuilder builder) throws Exception;
071}