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.core.value;
17
18 import java.lang.reflect.Method;
19 import java.lang.reflect.Modifier;
20
21 /**
22 * Translates enumeration values from their string representation. If the
23 * enumeration provides a static fromString method, this method will be used.
24 * Otherwise the name of the enumeration element is used for the translation
25 * task.
26 *
27 * @param <T> the type of the enumeration translated by this helper.
28 */
29 final class EnumIdTranslator<T extends Enum<T>>
30 {
31 // ********************************* Fields *********************************
32
33 // --- constants ------------------------------------------------------------
34
35 // --- members --------------------------------------------------------------
36
37 /**
38 * The wrapped enumeration type.
39 */
40 private final Class<T> enumType;
41
42 /**
43 * The method used to create an enumeration element from its string
44 * representation. The value is <code>null</code>, if no static
45 * <code>fromString</code> method is provided.
46 */
47 private final Method fromStringMethod;
48
49 // ****************************** Initializer *******************************
50
51 // ****************************** Constructors ******************************
52
53 EnumIdTranslator(final Class<T> enumType)
54 {
55 this.enumType = enumType;
56 this.fromStringMethod = calcMethod(enumType);
57 }
58
59 // ****************************** Inner Classes *****************************
60
61 // ********************************* Methods ********************************
62
63 // --- init -----------------------------------------------------------------
64
65 private static Method calcMethod(final Class<?> enumType)
66 {
67 try
68 {
69 final Method method = enumType.getMethod("fromString", String.class);
70 if (Modifier.isStatic(method.getModifiers()))
71 {
72 return method;
73 }
74 }
75 catch (final Exception e)
76 {
77 // return null at the end.
78 }
79 return null;
80 }
81
82 // --- get&set --------------------------------------------------------------
83
84 // --- business -------------------------------------------------------------
85
86 @SuppressWarnings("unchecked")
87 T fromString(final String valueAsString)
88 {
89 if (fromStringMethod != null)
90 {
91 try
92 {
93 final T value = (T) fromStringMethod.invoke(enumType, valueAsString);
94 return value;
95 }
96 catch (final Exception e)
97 {
98 // return enum valueOf at the end.
99 }
100 }
101 return Enum.valueOf(enumType, valueAsString);
102 }
103
104 // --- object basics --------------------------------------------------------
105
106 }