1 /*
2 * Copyright 2012-2013 smartics, Kronseder & Reiner GmbH
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 package de.smartics.properties.spi.config.domain.key;
17
18 import java.util.ServiceLoader;
19
20 import org.slf4j.Logger;
21 import org.slf4j.LoggerFactory;
22
23 /**
24 * Provides access to the manager and configuration key implementations.
25 */
26 public final class ConfigurationKeyContextManager
27 {
28 // ********************************* Fields *********************************
29
30 // --- constants ------------------------------------------------------------
31
32 /**
33 * The singleton to provide access to the manager and configuration key
34 * implementations.
35 */
36 public static final ConfigurationKeyContextManager INSTANCE =
37 new ConfigurationKeyContextManager();
38
39 // --- members --------------------------------------------------------------
40
41 /**
42 * Reference to the logger for this instance.
43 */
44 private final Logger log = LoggerFactory
45 .getLogger(ConfigurationKeyContextManager.class);
46
47 /**
48 * The configured context instance to access configuration key helpers.
49 */
50 private final ConfigurationKeyContext context; // NOPMD
51
52 // ****************************** Initializer *******************************
53
54 // ****************************** Constructors ******************************
55
56 /**
57 * Default constructor.
58 */
59 private ConfigurationKeyContextManager()
60 {
61 this.context = createContext();
62 }
63
64 // ****************************** Inner Classes *****************************
65
66 // ********************************* Methods ********************************
67
68 // --- init -----------------------------------------------------------------
69
70 @SuppressWarnings("unchecked")
71 private ConfigurationKeyContext createContext()
72 {
73 final ServiceLoader<ConfigurationKeyContext> loader =
74 ServiceLoader.load(ConfigurationKeyContext.class);
75
76 ConfigurationKeyContext current = null;
77 for (final ConfigurationKeyContext context : loader)
78 {
79 if (current == null)
80 {
81 current = context;
82 }
83 else
84 {
85 log.debug(String.format(
86 "Multiple instances. Using '%s', found instance of '%s'.", current
87 .getClass().getName(), context.getClass().getName()));
88 }
89 }
90
91 if (current == null)
92 {
93 final String defaultTypeName =
94 "de.smartics.properties.impl.config.domain.key.envapp.EnvAppConfigurationKeyContext";
95 try
96 {
97 final Class<ConfigurationKeyContext> defaultType =
98 (Class<ConfigurationKeyContext>) Class.forName(defaultTypeName);
99 current = defaultType.newInstance();
100 }
101 catch (final Exception e)
102 {
103 throw new IllegalStateException(
104 String
105 .format(
106 "Cannot find configuration key context and cannot create default: %s",
107 defaultTypeName));
108 }
109 }
110
111 return current;
112 }
113
114 // --- get&set --------------------------------------------------------------
115
116 /**
117 * Returns the configured context instance to access configuration key
118 * helpers.
119 *
120 * @return the configured context instance to access configuration key
121 * helpers.
122 */
123 public ConfigurationKeyContext context()
124 {
125 return context;
126 }
127
128 // --- business -------------------------------------------------------------
129
130 // --- object basics --------------------------------------------------------
131
132 }