1 /*
2 * Grapht, an open source dependency injector.
3 * Copyright 2014-2015 various contributors (see CONTRIBUTORS.txt)
4 * Copyright 2010-2014 Regents of the University of Minnesota
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU Lesser General Public License as
8 * published by the Free Software Foundation; either version 2.1 of the
9 * License, or (at your option) any later version.
10 *
11 * This program is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
13 * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
14 * details.
15 *
16 * You should have received a copy of the GNU General Public License along with
17 * this program; if not, write to the Free Software Foundation, Inc., 51
18 * Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
19 */
20 package org.grouplens.grapht.util;
21
22 import com.google.common.base.Supplier;
23
24 import javax.annotation.Nonnull;
25 import javax.annotation.Nullable;
26 import javax.inject.Provider;
27
28 /**
29 * Utility methods for providers.
30 *
31 * @since 0.6
32 * @author <a href="http://grouplens.org">GroupLens Research</a>
33 */
34 public final class Providers {
35 private Providers() {}
36
37 public static <T> Provider<T> of(@Nonnull T object) {
38 return new InstanceProvider<T>(object, object.getClass());
39 }
40
41 public static <T> Provider<T> of(@Nullable T object, Class<?> type) {
42 return new InstanceProvider<T>(object, type);
43 }
44
45 public static <T> Provider<T> memoize(@Nonnull Provider<T> inner) {
46 return new MemoizingProvider<T>(inner);
47 }
48
49 /**
50 * Convert a supplier to a provider.
51 * @param supplier The supplier.
52 * @param type The supplier's return type (to help the injector).
53 * @param <T> The type returned from the supplier.
54 * @return A provider.
55 */
56 public static <T> Provider<T> fromSupplier(final Supplier<T> supplier, final Class<T> type) {
57 return new TypedProvider<T>() {
58 @Override
59 public Class<?> getProvidedType() {
60 return type;
61 }
62
63 @Override
64 public T get() {
65 return supplier.get();
66 }
67 };
68 }
69 }