1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 */
19 package org.apache.onami.factoryannotation;
20
21 import java.lang.annotation.Annotation;
22
23 import com.google.inject.Injector;
24
25 /**
26 * The interface to describe a FactoryAnnotationProvider bound by {@link FactoryAnnotationModule} to the Guice
27 * {@link Injector}. <h3>Implementing a FactoryAnnotationProvider</h3> An {@link FactoryAnnotationProvider} is a special
28 * provider to return the actual instance of a injection type in combination with the actual factory annotation at the
29 * injection point. At this point we omit the UserEntity class. It can be a simple POJO, a JPA entity or whatever class
30 * you can image.
31 *
32 * <pre>
33 * public class UserEntityProvider implements FactoryAnnotationProvider<UserEntity, User> {
34 *
35 * {@literal @}Override
36 * public UserEntity buildValue(final User annotation) {
37 * return getRealEntityById(annotation.byId());
38 * }
39 *
40 * {@literal @}Override
41 * public Class<UserEntity> getInjectionType() {
42 * return UserEntity.class;
43 * }
44 *
45 * private UserEntity getRealEntityById(int id) {
46 * ...
47 * }
48 *
49 * }
50 * </pre>
51 *
52 * @param <T> The type to be injected
53 * @param <A> Annotation type where injection happens
54 */
55 public interface FactoryAnnotationProvider<T, A extends Annotation>
56 {
57
58 /**
59 * Returns the type of injection points that should be captured for provision.
60 */
61 Class<T> getInjectionType();
62
63 /**
64 * <p>
65 * The implementation of this method is responsible for building / requesting the instance that is referenced by the
66 * actual injection points annotation to the annotation type bound at configuration time.
67 * </p>
68 * <p>
69 * For more information see {@link FactoryAnnotationModule}.
70 * </p>
71 *
72 * @param annotation The actual annotation of the bound annotation type at the provision injection point.
73 * @return The actual instance for a given annotation based value.
74 */
75 T buildValue( A annotation );
76
77 }