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                                                                             *
008// *                                                                                                                         *
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011// * specific language governing permissions and limitations under the License.                                              *
012// ***************************************************************************************************************************
013package org.apache.juneau.rest;
014
015import org.apache.juneau.*;
016import org.apache.juneau.rest.annotation.*;
017
018/**
019 * Class used to resolve {@link Class} objects to instances.
020 *
021 * <p>
022 * Used to convert classes defined via {@link Rest#children() @Rest(children)} into child instances.
023 *
024 * <p>
025 * Subclasses can be created to provide customized resource resolution.
026 * These can be associated with REST resources in one of the following ways:
027 * <ul>
028 *    <li>{@link Rest#resourceResolver() @Rest(resourceResolver)} annotation.
029 *    <li>{@link RestContextBuilder#resourceResolver(Class)}/{@link RestContextBuilder#resourceResolver(RestResourceResolver)}
030 *       methods.
031 * </ul>
032 *
033 * Implementations must provide one of the following public constructors:
034 * <ul>
035 *    <li>RestResourceResolver()
036 *    <li>RestResourceResolver(RestContext)
037 * </ul>
038 *
039 * <ul class='seealso'>
040 *    <li class='link'>{@doc juneau-rest-server.Instantiation.ResourceResolvers}
041 * </ul>
042 */
043public interface RestResourceResolver extends ResourceResolver {
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 Rest#children() @Rest(children)} annotation.
065    * @param c The class to resolve.
066    * @param builder The initialization configuration for the resource.
067    * @param args Optional arguments to pass to constructor
068    * @return The instance of that class.
069    * @throws Exception If class could not be resolved.
070    */
071   <T> T resolve(Object parent, Class<T> c, RestContextBuilder builder, Object...args) throws Exception;
072}