1 /**
2 * This file Copyright (c) 2013-2018 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.i18nsystem.util;
35
36 import java.lang.reflect.Method;
37 import java.lang.reflect.ParameterizedType;
38 import java.lang.reflect.Type;
39 import java.lang.reflect.WildcardType;
40 import java.util.Map;
41
42 /**
43 * Utility methods to work with generics.
44 */
45 public class GenericsUtils {
46
47 /**
48 * Gets the generic parameter of the return type of the given method.
49 * If the return type of the given method is not parameterized, returns the return type of the method.
50 * If the return type of the given method has a single type parameter, return that type.
51 * If the return type of the given method is a Map and has two type parameters, return the second, which is normally that of the values.
52 */
53 public static Type getGenericTypeOfReturnType(Method method) {
54 final Type returnType = method.getGenericReturnType();
55
56 if (!(returnType instanceof ParameterizedType)) {
57 // return type is not parameterized, so we look at that
58 return returnType;
59 } else {
60 return getGenericParameterType((ParameterizedType) returnType);
61 }
62 }
63
64 public static Type getGenericParameterType(ParameterizedType paramType) {
65 // Frankly, I'm not quite sure why raw type would not be a class.
66 if (!(paramType.getRawType() instanceof Class)) {
67 throw new IllegalStateException("Raw type of " + paramType + " is not a Class; bailing.");
68 }
69
70 final Class<?> rawType = (Class<?>) paramType.getRawType();
71 final Type[] actualTypeArguments = paramType.getActualTypeArguments();
72 final Type actualTypeArgument;
73 // if the method parameter has a single generic type
74 if (actualTypeArguments.length == 1) {
75 actualTypeArgument = actualTypeArguments[0];
76 } else {
77 // for map, we look at the second generic type (the Value)
78 if (Map.class.isAssignableFrom(rawType) && actualTypeArguments.length == 2) {
79 actualTypeArgument = actualTypeArguments[1];
80 } else {
81 throw new IllegalStateException("Don't know what to do with multiple generics on " + paramType);
82 }
83 }
84
85 if (actualTypeArgument instanceof WildcardType) {
86 final WildcardType wildcardType = ((WildcardType) actualTypeArgument);
87 if (wildcardType.getLowerBounds().length > 0) {
88 throw new IllegalStateException("Don't know what do with WildcardType which has lower bounds: " + actualTypeArgument);
89 } else if (wildcardType.getUpperBounds().length > 1) {
90 throw new IllegalStateException("Don't know what do with WildcardType which has more than one upper bound: " + actualTypeArgument);
91 } else {
92 return wildcardType.getUpperBounds()[0];
93 }
94 }
95 return actualTypeArgument;
96 }
97 }