| // Copyright 2007, 2008, 2011 The Apache Software Foundation |
| // |
| // Licensed 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.tapestry5.ioc.services; |
| |
| import org.apache.tapestry5.ioc.AnnotationProvider; |
| import org.apache.tapestry5.ioc.ObjectLocator; |
| import org.apache.tapestry5.ioc.ObjectProvider; |
| import org.apache.tapestry5.ioc.annotations.UsesOrderedConfiguration; |
| |
| /** |
| * A service that acts as a chain-of-command over a number of {@link org.apache.tapestry5.ioc.ObjectProvider}, but |
| * allows for the case where no object may be provided. |
| * <p/> |
| * This service is itself a key part of Tapestry's general injection mechanism; it is used when instantiating a service |
| * implementation instance, invoking module methods (service builder, decorator, or contribution methods), when |
| * {@linkplain ObjectLocator#autobuild(Class) autobuilding} objects of any type. |
| * <p/> |
| * As of Tapestry 5.3, the MasterObjectProvider allows injection of {@link org.apache.tapestry5.ioc.OperationTracker} as a |
| * special case (not based on a contributed ObjectProvider). |
| */ |
| @UsesOrderedConfiguration(ObjectProvider.class) |
| public interface MasterObjectProvider |
| { |
| /** |
| * Provides an object based on an expression. The process of providing objects occurs within a particular |
| * <em>context</em>, which will typically be a service builder method, service contributor method, or service |
| * decorator method. The locator parameter provides access to the services visible <em>to that context</em>. |
| * <p/> |
| * When the value is required and no {@link ObjectProvider} provided a non-null value, then {@link |
| * ObjectLocator#getService(Class, Class[])} is invoked (with no marker annotations), |
| * to provide a uniquely matching service, or throw a failure exception |
| * if no <em>single</em> service can be found. |
| * |
| * @param objectType the expected object type |
| * @param annotationProvider provides access to annotations (typically, the field or parameter to which an |
| * injection-related annotation is attached); annotations on the field or parameter may |
| * also be used when resolving the desired object |
| * @param locator locator for the <em>context</em> in which the provider is being used |
| * @param required if true (normal case) a value must be provided; if false then it is allowed for no |
| * ObjectProvider to provide a value, and this method may return null to indicate the |
| * failure |
| * @param <T> |
| * @return the requested object, or null if this object provider can not supply an object |
| * @throws RuntimeException if the expression can not be evaluated, or the type of object identified is not |
| * assignable to the type specified by the objectType parameter |
| */ |
| <T> T provide(Class<T> objectType, AnnotationProvider annotationProvider, ObjectLocator locator, boolean required); |
| } |