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.reflect;
21
22 import javax.inject.Provider;
23
24 /**
25 * Abstract implementation of {@link SatisfactionVisitor}. All methods delegate to
26 * {@link #visitDefault()}, which in turn returns a default value.
27 *
28 * @author <a href="http://grouplens.org">GroupLens Research</a>
29 * @since 0.5
30 */
31 public abstract class AbstractSatisfactionVisitor<T> implements SatisfactionVisitor<T> {
32 protected final T defaultValue;
33
34 /**
35 * Construct a visitor with a null default.
36 */
37 public AbstractSatisfactionVisitor() {
38 this(null);
39 }
40
41 /**
42 * Construct a visitor with the specified default value.
43 *
44 * @param dft The default value to be returned by {@link #visitDefault()}.
45 */
46 public AbstractSatisfactionVisitor(T dft) {
47 defaultValue = dft;
48 }
49
50 /**
51 * Default method called when other methods are not overridden. The default implementation
52 * returns the default value provided to {@link #AbstractSatisfactionVisitor(Object)}.
53 * @return The return value.
54 */
55 public T visitDefault() {
56 return defaultValue;
57 }
58
59 @Override
60 public T visitNull() {
61 return visitDefault();
62 }
63
64 @Override
65 public T visitClass(Class<?> clazz) {
66 return visitDefault();
67 }
68
69 @Override
70 public T visitInstance(Object instance) {
71 return visitDefault();
72 }
73
74 @Override
75 public T visitProviderClass(Class<? extends Provider<?>> pclass) {
76 return visitDefault();
77 }
78
79 @Override
80 public T visitProviderInstance(Provider<?> provider) {
81 return visitDefault();
82 }
83 }