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