1 /**
2 * This file Copyright (c) 2010-2010 Magnolia International
3 * Ltd. (http://www.magnolia-cms.com). All rights reserved.
4 *
5 *
6 * This file is dual-licensed under both the Magnolia
7 * Network Agreement and the GNU General Public License.
8 * You may elect to use one or the other of these licenses.
9 *
10 * This file is distributed in the hope that it will be
11 * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
12 * implied warranty of MERCHANTABILITY or FITNESS FOR A
13 * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
14 * Redistribution, except as permitted by whichever of the GPL
15 * or MNA you select, is prohibited.
16 *
17 * 1. For the GPL license (GPL), you can redistribute and/or
18 * modify this file under the terms of the GNU General
19 * Public License, Version 3, as published by the Free Software
20 * Foundation. You should have received a copy of the GNU
21 * General Public License, Version 3 along with this program;
22 * if not, write to the Free Software Foundation, Inc., 51
23 * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
24 *
25 * 2. For the Magnolia Network Agreement (MNA), this file
26 * and the accompanying materials are made available under the
27 * terms of the MNA which accompanies this distribution, and
28 * is available at http://www.magnolia-cms.com/mna.html
29 *
30 * Any modifications to this file must keep this entire header
31 * intact.
32 *
33 */
34 package info.magnolia.objectfactory;
35
36 import info.magnolia.cms.core.SystemProperty;
37 import org.apache.commons.lang.StringUtils;
38
39 /**
40 * Entry point to the currently configured ClassFactory.
41 *
42 * @see info.magnolia.objectfactory.ClassFactory
43 *
44 * @author gjoseph
45 * @version $Revision: $ ($Author: $)
46 */
47 public class Classes {
48 private final static org.slf4j.Logger log = org.slf4j.LoggerFactory.getLogger(Classes.class);
49
50 /**
51 * Convenience/shortcut method for instantiating new classes.
52 * @see info.magnolia.objectfactory.ClassFactory
53 * @see #getClassFactory()
54 * @throws ClassNotFoundException
55 * @throws MgnlInstantiationException
56 */
57 public static <T> T newInstance(String className, Object... params) throws ClassNotFoundException {
58 final ClassFactory cf = getClassFactory();
59 final Class<T> cl = cf.forName(className);
60 return cf.newInstance(cl, params);
61 }
62
63 /**
64 * Convenience/shortcut for {@link #newInstance(String, Object...)}, returning null both in case
65 * of a ClassNotFoundException or if the class could not be instantiated (which could be related to the parameters, etc)
66 */
67 public static <T> T quietNewInstance(String className, Object... params) {
68 try {
69 return Classes.<T>newInstance(className, params);
70 } catch (ClassNotFoundException e) {
71 log.warn("Couldn't find class with name {}", className);
72 return null;
73 } catch (MgnlInstantiationException e) {
74 log.warn("Couldn't instantiate {}: {}", className, e.getMessage());
75 return null;
76 }
77 }
78
79 public static ClassFactory getClassFactory() {
80 return cfp.current();
81 }
82
83 // this field should be final but isn't, for tests' sake
84 private static ClassFactoryProvider cfp = new ClassFactoryProvider(new DefaultClassFactory());
85
86 /**
87 * ClassFactoryProvider is used to hide the "swapability" of ClassFactory.
88 * This current implementation checks the current instance versus the configured property
89 * on every call.
90 * TODO : This could possibly be optimized or "blocked" as soon as we can now this property has indeed been configured.
91 * I don't think the above would be interesting until we can do some refactoring of the ConfigLoader, PropertiesInitializer and SystemProperty classes.
92 */
93 protected static class ClassFactoryProvider {
94 private ClassFactory initial;
95 private ClassFactory current;
96 private boolean swapping;
97
98 public ClassFactoryProvider(ClassFactory initial) {
99 this.initial = initial;
100 this.current = initial;
101 }
102
103 public ClassFactory current() {
104 check();
105 return current;
106 }
107
108 private void check() {
109 final String configuredCFClassName = getCurrentlyConfiguredClassName();
110 final String currentCFClassName = current.getClass().getName();
111 if (StringUtils.isNotEmpty(configuredCFClassName) && !currentCFClassName.equals(configuredCFClassName) && !swapping) {
112 // we need to swap this instance, but other calls should not try to do it until we're done
113 swapping = true;
114
115 // whichever ClassFactory is registered will be instantiated with the initial ClassFactory.
116 try {
117 final Class<ClassFactory> c = initial.forName(configuredCFClassName);
118 current = initial.newInstance(c);
119 } catch (ClassNotFoundException e) {
120 log.error("Could not find {}, will keep on using {} for now", configuredCFClassName, current.getClass().getSimpleName());
121 }
122 swapping = false;
123 }
124 }
125
126 protected String getCurrentlyConfiguredClassName() {
127 return SystemProperty.getProperty(ClassFactory.class.getName());
128 }
129 }
130
131 }