001// Copyright 2006, 2007, 2010, 2011, 2014 The Apache Software Foundation
002//
003// Licensed under the Apache License, Version 2.0 (the "License");
004// you may not use this file except in compliance with the License.
005// You may obtain a copy of the License at
006//
007// http://www.apache.org/licenses/LICENSE-2.0
008//
009// Unless required by applicable law or agreed to in writing, software
010// distributed under the License is distributed on an "AS IS" BASIS,
011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012// See the License for the specific language governing permissions and
013// limitations under the License.
014
015package org.apache.tapestry5.ioc;
016
017import org.apache.tapestry5.ioc.annotations.Inject;
018
019import java.lang.annotation.Annotation;
020
021/**
022 * Defines an object which can provide access to services defined within a {@link org.apache.tapestry5.ioc.Registry}, or
023 * to objects or object instances available by other means. Services are accessed via service id, or
024 * (when appropriate)
025 * by just service interface. The Registry itself implements this interface, as does
026 * {@link org.apache.tapestry5.ioc.ServiceResources}.
027 */
028public interface ObjectLocator
029{
030    /**
031     * Obtains a service via its unique service id. Returns the service's proxy. The service proxy
032     * implements the same
033     * interface as the actual service, and is used to instantiate the actual service only as needed
034     * (this is
035     * transparent to the application).
036     *
037     * @param <T>
038     * @param serviceId        unique Service id used to locate the service object (may contain <em>symbols</em>,
039     *                         which
040     *                         will be expanded), case is ignored
041     * @param serviceInterface the interface implemented by the service (or an interface extended by the service
042     *                         interface)
043     * @return the service instance
044     * @throws RuntimeException if the service is not defined, or if an error occurs instantiating it
045     */
046    <T> T getService(String serviceId, Class<T> serviceInterface);
047
048    /**
049     * Locates a service given a service interface and (optionally) some marker annotation types. A single service must implement the service
050     * interface (which                                                   * can be hard to guarantee) and by marked by all the marker types. The search takes into account inheritance of the service interface
051     * (not the service <em>implementation</em>), which may result in a failure due to extra
052     * matches.
053     *
054     * @param serviceInterface the interface the service implements
055     * @return the service's proxy
056     * @throws RuntimeException if the service does not exist (this is considered programmer error), or multiple
057     *                          services directly implement, or extend from, the service interface
058     * @see org.apache.tapestry5.ioc.annotations.Marker
059     */
060    <T> T getService(Class<T> serviceInterface);
061
062    /**
063     * Locates a service given a service interface and (optionally) some marker annotation types. A single service must implement the service
064     * interface (which                                                   * can be hard to guarantee) and by marked by all the marker types. The search takes into account inheritance of the service interface
065     * (not the service <em>implementation</em>), which may result in a failure due to extra
066     * matches.        The ability to specify marker annotation types was added in 5.3
067     *
068     * @param serviceInterface the interface the service implements
069     * @param markerTypes      Markers used to select a specific service that implements the interface
070     * @return the service's proxy
071     * @throws RuntimeException if the service does not exist (this is considered programmer error), or multiple
072     *                          services directly implement, or extend from, the service interface
073     * @see org.apache.tapestry5.ioc.annotations.Marker
074     * @since 5.3
075     */
076    <T> T getService(Class<T> serviceInterface, Class<? extends Annotation>... markerTypes);
077
078    /**
079     * Obtains an object indirectly, using the {@link org.apache.tapestry5.ioc.services.MasterObjectProvider} service.
080     *
081     * @param objectType         the type of object to be returned
082     * @param annotationProvider provides access to annotations on the field or parameter for which a value is to
083     *                           be
084     *                           obtained, which may be utilized in selecting an appropriate object, use
085     *                           <strong>null</strong> when annotations are not available (in which case, selection
086     *                           will
087     *                           be based only on the object type)
088     * @param <T>
089     * @return the requested object
090     * @see ObjectProvider
091     */
092    <T> T getObject(Class<T> objectType, AnnotationProvider annotationProvider);
093
094    /**
095     * Autobuilds a class by finding the public constructor with the most parameters. Services and other resources or
096     * dependencies will be injected into the parameters of the constructor and into private fields marked with the
097     * {@link Inject} annotation. There are two cases: constructing a service implementation, and constructing
098     * an arbitrary object. In the former case, many <em>service resources</em> are also available for injection, not
099     * just dependencies or objects provided via
100     * {@link MasterObjectProvider#provide(Class, AnnotationProvider, ObjectLocator, boolean)}.
101     *
102     * @param <T>
103     * @param clazz the type of object to instantiate
104     * @return the instantiated instance
105     * @throws RuntimeException if the autobuild fails
106     * @see MasterObjectProvider
107     */
108    <T> T autobuild(Class<T> clazz);
109
110    /**
111     * Preferred version of {@link #autobuild(Class)} that tracks the operation using
112     * {@link OperationTracker#invoke(String, Invokable)}.
113     *
114     * @param <T>
115     * @param description description used with {@link OperationTracker}
116     * @param clazz       the type of object to instantiate
117     * @return the instantiated instance
118     * @throws RuntimeException if the autobuild fails
119     * @see MasterObjectProvider
120     * @since 5.2.0
121     */
122    <T> T autobuild(String description, Class<T> clazz);
123
124    /**
125     * Creates a proxy. The proxy will defer invocation of {@link #autobuild(Class)} until
126     * just-in-time (that is, first method invocation). In a limited number of cases, it is necessary to use such a
127     * proxy to prevent service construction cycles, particularly when contributing (directly or indirectly) to the
128     * {@link org.apache.tapestry5.ioc.services.MasterObjectProvider} (which is itself at the heart
129     * of autobuilding).
130     * <p/>
131     * If the class file for the class is a file on the file system (not a file packaged in a JAR), then the proxy will
132     * <em>autoreload</em>: changing the class file will result in the new class being reloaded and re-instantiated
133     * (with dependencies).
134     *
135     * @param <T>
136     * @param interfaceClass      the interface implemented by the proxy
137     * @param implementationClass a concrete class that implements the interface
138     * @return a proxy
139     * @see #autobuild(Class)
140     */
141    <T> T proxy(Class<T> interfaceClass, Class<? extends T> implementationClass);
142}