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.proxy;
17
18 import de.smartics.properties.api.config.domain.SerializableConfigurationProperties;
19 import de.smartics.properties.api.core.annotations.PropertySet;
20
21 /**
22 * This factory creates a implementation object via a java dynamic proxy for a
23 * given properties interface. Using this object it is possible to access the
24 * properties and when defined in the given interface the keys and property
25 * descriptions can be accessed.
26 */
27 public final class PropertyConfigurationObjectBuilder
28 {
29 // ********************************* Fields *********************************
30
31 // --- constants ------------------------------------------------------------
32
33 // --- members --------------------------------------------------------------
34
35 // ****************************** Initializer *******************************
36
37 // ****************************** Constructors ******************************
38
39 /**
40 * The default message suffix.
41 */
42 private static final String MESSAGE =
43 "Only classes that represent an"
44 + " interface and that interface must have a 'PropertySet'"
45 + " annotation are allowed.";
46
47 /**
48 * Default constructor.
49 */
50 public PropertyConfigurationObjectBuilder()
51 {
52 }
53
54 // ****************************** Inner Classes *****************************
55
56 // ********************************* Methods ********************************
57
58 // --- init -----------------------------------------------------------------
59
60 // --- get&set --------------------------------------------------------------
61
62 // --- business -------------------------------------------------------------
63
64 /**
65 * Build the object that contains the properties information for the given
66 * properties interface. The interface must be provided through its class
67 * object and has to have a {@link PropertySet} annotation.
68 *
69 * @param propertiesInterface the properties interface as class object with an
70 * {@link PropertySet} annotation.
71 * @param configurationProperties the configuration properties that shall be
72 * used to access the properties.
73 * @param <T> to provide a type safe access to the properties the returned
74 * object implements the given properties interface.
75 * @return the object that contains the properties information for the given
76 * properties interface.
77 * @throws NotAPropertySetAnnotatedInterfaceException when the given class
78 * does not represent an interface and this interface is not
79 * annotated with {@link PropertySet} or when null.
80 */
81 public <T> T build(final Class<T> propertiesInterface,
82 final SerializableConfigurationProperties configurationProperties)
83 throws NotAPropertySetAnnotatedInterfaceException
84 {
85 checkForValidPropertiesInterface(propertiesInterface);
86 final T propertiesObject =
87 buildObject(propertiesInterface, configurationProperties);
88 return propertiesObject;
89 }
90
91 @SuppressWarnings("unchecked")
92 private <T> T buildObject(final Class<T> propertiesInterface,
93 final SerializableConfigurationProperties configurationProperties)
94 {
95 final T propertiesObject =
96 (T) java.lang.reflect.Proxy.newProxyInstance(
97 propertiesInterface.getClassLoader(),
98 new Class[] { propertiesInterface },
99 new PropertiesProxyInvocationHandler(configurationProperties));
100 return propertiesObject;
101 }
102
103 private <T> void checkForValidPropertiesInterface(
104 final Class<T> propertiesInterface)
105 {
106 checkNull(propertiesInterface);
107 checkIfInterface(propertiesInterface);
108 checkIfCorrectAnnotated(propertiesInterface);
109 }
110
111 private <T> void checkNull(final Class<T> propertiesInterface)
112 {
113 if (propertiesInterface == null)
114 {
115 throw new NotAPropertySetAnnotatedInterfaceException(
116 "Null is not allowed." + MESSAGE);
117 }
118 }
119
120 private <T> void checkIfInterface(final Class<T> propertiesInterface)
121 {
122 if (!propertiesInterface.isInterface())
123 {
124 throw new NotAPropertySetAnnotatedInterfaceException("Not an interface."
125 + MESSAGE);
126 }
127 }
128
129 private <T> void checkIfCorrectAnnotated(final Class<T> propertiesInterface)
130 {
131 final PropertySet propertySetAnnotation =
132 propertiesInterface.getAnnotation(PropertySet.class);
133 if (propertySetAnnotation == null)
134 {
135 throw new NotAPropertySetAnnotatedInterfaceException(
136 "Not a valid annotated interface." + MESSAGE);
137 }
138 }
139
140 // --- object basics --------------------------------------------------------
141
142 }