1 /*
2 * *************************************************************************************************************************************************************
3 *
4 * TheseFoolishThings: Miscellaneous utilities
5 * http://tidalwave.it/projects/thesefoolishthings
6 *
7 * Copyright (C) 2009 - 2024 by Tidalwave s.a.s. (http://tidalwave.it)
8 *
9 * *************************************************************************************************************************************************************
10 *
11 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License.
12 * You may obtain a copy of the License at
13 *
14 * http://www.apache.org/licenses/LICENSE-2.0
15 *
16 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
17 * CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.
18 *
19 * *************************************************************************************************************************************************************
20 *
21 * git clone https://bitbucket.org/tidalwave/thesefoolishthings-src
22 * git clone https://github.com/tidalwave-it/thesefoolishthings-src
23 *
24 * *************************************************************************************************************************************************************
25 */
26 package it.tidalwave.util;
27
28 import java.lang.annotation.Annotation;
29 import java.lang.reflect.Array;
30 import java.lang.reflect.Field;
31 import java.lang.reflect.GenericArrayType;
32 import java.lang.reflect.InvocationTargetException;
33 import java.lang.reflect.ParameterizedType;
34 import java.lang.reflect.Type;
35 import java.lang.reflect.TypeVariable;
36 import javax.annotation.CheckForNull;
37 import javax.annotation.Nonnull;
38 import java.util.ArrayList;
39 import java.util.Arrays;
40 import java.util.HashMap;
41 import java.util.List;
42 import java.util.Map;
43 import lombok.extern.slf4j.Slf4j;
44 import static java.util.Objects.requireNonNull;
45 import static java.util.stream.Collectors.*;
46 import static it.tidalwave.util.ShortNames.*;
47
48 /***************************************************************************************************************************************************************
49 *
50 * Adapted from <a href="http://www.artima.com/weblogs/viewpost.jsp?thread=208860">this article</a>
51 *
52 * @author Ian Robertson
53 * @author Fabrizio Giudici
54 *
55 **************************************************************************************************************************************************************/
56 @Slf4j
57 public class ReflectionUtils
58 {
59 private static final List<String> INJECT_CLASS_NAMES = List.of("javax.inject.Inject", "jakarta.inject.Inject");
60
61 /***********************************************************************************************************************************************************
62 * Get the actual type arguments a subclass has used to extend a generic base class.
63 *
64 * @param <T> the static type of the base class
65 * @param baseClass the base class
66 * @param childClass the subclass
67 * @return a list of the raw classes for the actual type arguments.
68 **********************************************************************************************************************************************************/
69 @Nonnull
70 public static <T> List<Class<?>> getTypeArguments (@Nonnull final Class<T> baseClass,
71 @Nonnull final Class<? extends T> childClass)
72 {
73 final Map<Type, Type> resolvedTypes = new HashMap<>();
74 Type type = childClass;
75
76 // start walking up the inheritance hierarchy until we hit baseClass
77 while (!baseClass.equals(getClass(type)))
78 {
79 if (type instanceof Class<?>)
80 {
81 // there is no useful information for us in raw types, so just keep going.
82 type = ((Class<?>)type).getGenericSuperclass();
83 }
84 else
85 {
86 final var parameterizedType = (ParameterizedType) type;
87 final var rawType = (Class<?>) parameterizedType.getRawType();
88 final var actualTypeArguments = parameterizedType.getActualTypeArguments();
89 final TypeVariable<?>[] typeParameters = rawType.getTypeParameters();
90
91 for (var i = 0; i < actualTypeArguments.length; i++)
92 {
93 resolvedTypes.put(typeParameters[i], actualTypeArguments[i]);
94 }
95
96 if (!rawType.equals(baseClass))
97 {
98 type = rawType.getGenericSuperclass();
99 }
100 }
101 }
102
103 // finally, for each actual type argument provided to baseClass, determine (if possible)
104 // the raw class for that type argument.
105 final Type[] actualTypeArguments;
106
107 if (type instanceof Class)
108 {
109 actualTypeArguments = ((Class<?>)type).getTypeParameters();
110 }
111 else
112 {
113 actualTypeArguments = ((ParameterizedType)type).getActualTypeArguments();
114 }
115
116 final var typeArgumentsAsClasses = new ArrayList<Class<?>>();
117
118 // resolve types by chasing down type variables.
119 for (var baseType : actualTypeArguments)
120 {
121 while (resolvedTypes.containsKey(baseType))
122 {
123 baseType = resolvedTypes.get(baseType);
124 }
125
126 typeArgumentsAsClasses.add(getClass(baseType));
127 }
128
129 return typeArgumentsAsClasses;
130 }
131
132 /***********************************************************************************************************************************************************
133 * Instantiates an object of the given class performing dependency injections through the constructor.
134 *
135 * @param <T> the generic type of the object to instantiate
136 * @param type the dynamic type of the object to instantiate; it is expected to have a single constructor
137 * @param beans the bag of objects to instantiate
138 * @return the new instance
139 * @throws RuntimeException if something fails
140 * @since 3.2-ALPHA-17
141 **********************************************************************************************************************************************************/
142 public static <T> T instantiateWithDependencies (@Nonnull final Class<? extends T> type,
143 @Nonnull final Map<Class<?>, Object> beans)
144 {
145 try
146 {
147 log.debug("instantiateWithDependencies({}, {})", shortName(type), shortIds(beans.values()));
148 final var constructors = type.getConstructors();
149
150 if (constructors.length > 1)
151 {
152 throw new RuntimeException("Multiple constructors in " + type);
153 }
154
155 final var parameters = Arrays.stream(constructors[0].getParameterTypes()).map(beans::get).collect(toList());
156
157 log.trace(">>>> ctor arguments: {}", shortIds(parameters));
158 return type.cast(constructors[0].newInstance(parameters.toArray()));
159 }
160 catch (InstantiationException | IllegalAccessException | InvocationTargetException e)
161 {
162 throw new RuntimeException(e);
163 }
164 }
165
166 /***********************************************************************************************************************************************************
167 * Performs dependency injection to an object by means of field introspection.
168 *
169 * @param object the object
170 * @param beans the bag of objects to instantiate
171 * @since 3.2-ALPHA-17
172 **********************************************************************************************************************************************************/
173 public static void injectDependencies (@Nonnull final Object object, @Nonnull final Map<Class<?>, Object> beans)
174 {
175 for (final var field : object.getClass().getDeclaredFields())
176 {
177 if (hasInjectAnnotation(field))
178 {
179 field.setAccessible(true);
180 final var type = field.getType();
181 final var dependency = beans.get(type);
182
183 if (dependency == null)
184 {
185 throw new RuntimeException("Can't inject " + object + "." + field.getName());
186 }
187
188 try
189 {
190 field.set(object, dependency);
191 }
192 catch (IllegalArgumentException | IllegalAccessException e)
193 {
194 throw new RuntimeException(e);
195 }
196 }
197 }
198 }
199
200 /***********************************************************************************************************************************************************
201 * Returns the class literal associated to the given type.
202 *
203 * @param type the type to inspect
204 * @return the class literal; it might be {@code null} if fails
205 **********************************************************************************************************************************************************/
206 @CheckForNull
207 public static Class<?> getClass (@Nonnull final Type type)
208 {
209 requireNonNull(type, "type");
210
211 if (type instanceof Class<?>)
212 {
213 return (Class<?>)type;
214 }
215 else if (type instanceof ParameterizedType)
216 {
217 return getClass(((ParameterizedType)type).getRawType());
218 }
219 else if (type instanceof GenericArrayType)
220 {
221 final var componentType = ((GenericArrayType)type).getGenericComponentType();
222 final var componentClass = getClass(componentType);
223
224 if (componentClass == null)
225 {
226 return null;
227 }
228
229 return Array.newInstance(componentClass, 0).getClass();
230 }
231 else
232 {
233 // throw new IllegalArgumentException(type.toString());
234 return null;
235 }
236 }
237
238 /***********************************************************************************************************************************************************
239 *
240 **********************************************************************************************************************************************************/
241 private static boolean hasInjectAnnotation (@Nonnull final Field field)
242 {
243 final var classLoader = Thread.currentThread().getContextClassLoader();
244
245 for (final var className : INJECT_CLASS_NAMES)
246 {
247 try
248 {
249 @SuppressWarnings("unchecked")
250 final var clazz = (Class<? extends Annotation>)classLoader.loadClass(className);
251
252 if (field.getAnnotation(clazz) != null)
253 {
254 return true;
255 }
256 }
257 catch (ClassNotFoundException ignored)
258 {
259 // try next
260 }
261 }
262
263 return false;
264 }
265 }