1 /*
2 * Copyright 2016 the original author or authors.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 package org.openehealth.ipf.commons.core.config;
18
19 import java.util.Collection;
20 import java.util.Optional;
21 import java.util.ServiceLoader;
22 import java.util.stream.Collectors;
23 import java.util.stream.Stream;
24 import java.util.stream.StreamSupport;
25
26 /**
27 * Lookup implementation of an interface type using {@link ServiceLoader}.
28 */
29 public class Lookup {
30
31 /**
32 * Returns the first implementation of T
33 *
34 * @param clazz interface
35 * @param <T> interface type
36 * @return first implementation of T, if any
37 */
38 public static <T> Optional<T> lookup(Class<T> clazz) {
39 return load(clazz).findFirst();
40 }
41
42 /**
43 * Returns all implementations of T
44 *
45 * @param clazz interface
46 * @param <T> interface type
47 * @return implementations of T or an empty collection
48 */
49 public static <T> Collection<? extends T> lookupAll(Class<T> clazz) {
50 return load(clazz).collect(Collectors.toList());
51 }
52
53 private static <T> Stream<T> load(Class<T> clazz) {
54 return StreamSupport.stream(ServiceLoader.load(clazz).spliterator(), false);
55 }
56
57 }