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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.apache.commons.lang3.reflect;
18  
19  import java.lang.reflect.Constructor;
20  import java.lang.reflect.InvocationTargetException;
21  import java.lang.reflect.Modifier;
22  
23  import org.apache.commons.lang3.ArrayUtils;
24  import org.apache.commons.lang3.ClassUtils;
25  import org.apache.commons.lang3.Validate;
26  
27  /**
28   * <p> Utility reflection methods focused on constructors, modeled after
29   * {@link MethodUtils}. </p>
30   *
31   * <h3>Known Limitations</h3> <h4>Accessing Public Constructors In A Default
32   * Access Superclass</h4> <p>There is an issue when invoking {@code public} constructors
33   * contained in a default access superclass. Reflection correctly locates these
34   * constructors and assigns them as {@code public}. However, an
35   * {@link IllegalAccessException} is thrown if the constructor is
36   * invoked.</p>
37   *
38   * <p>{@link ConstructorUtils} contains a workaround for this situation: it
39   * will attempt to call {@link java.lang.reflect.AccessibleObject#setAccessible(boolean)} on this constructor. If this
40   * call succeeds, then the method can be invoked as normal. This call will only
41   * succeed when the application has sufficient security privileges. If this call
42   * fails then a warning will be logged and the method may fail.</p>
43   *
44   * @since 2.5
45   */
46  public class ConstructorUtils {
47  
48      /**
49       * <p>ConstructorUtils instances should NOT be constructed in standard
50       * programming. Instead, the class should be used as
51       * {@code ConstructorUtils.invokeConstructor(cls, args)}.</p>
52       *
53       * <p>This constructor is {@code public} to permit tools that require a JavaBean
54       * instance to operate.</p>
55       */
56      public ConstructorUtils() {
57          super();
58      }
59  
60      /**
61       * <p>Returns a new instance of the specified class inferring the right constructor
62       * from the types of the arguments.</p>
63       * 
64       * <p>This locates and calls a constructor.
65       * The constructor signature must match the argument types by assignment compatibility.</p>
66       *
67       * @param <T> the type to be constructed
68       * @param cls  the class to be constructed, not {@code null}
69       * @param args  the array of arguments, {@code null} treated as empty
70       * @return new instance of {@code cls}, not {@code null}
71       *
72       * @throws NullPointerException if {@code cls} is {@code null}
73       * @throws NoSuchMethodException if a matching constructor cannot be found
74       * @throws IllegalAccessException if invocation is not permitted by security
75       * @throws InvocationTargetException if an error occurs on invocation
76       * @throws InstantiationException if an error occurs on instantiation
77       * @see #invokeConstructor(java.lang.Class, java.lang.Object[], java.lang.Class[])
78       */
79      public static <T> T invokeConstructor(final Class<T> cls, Object... args)
80              throws NoSuchMethodException, IllegalAccessException, InvocationTargetException,
81              InstantiationException {
82          args = ArrayUtils.nullToEmpty(args);
83          final Class<?> parameterTypes[] = ClassUtils.toClass(args);
84          return invokeConstructor(cls, args, parameterTypes);
85      }
86  
87      /**
88       * <p>Returns a new instance of the specified class choosing the right constructor
89       * from the list of parameter types.</p>
90       * 
91       * <p>This locates and calls a constructor.
92       * The constructor signature must match the parameter types by assignment compatibility.</p>
93       *
94       * @param <T> the type to be constructed
95       * @param cls  the class to be constructed, not {@code null}
96       * @param args  the array of arguments, {@code null} treated as empty
97       * @param parameterTypes  the array of parameter types, {@code null} treated as empty
98       * @return new instance of {@code cls}, not {@code null}
99       *
100      * @throws NullPointerException if {@code cls} is {@code null}
101      * @throws NoSuchMethodException if a matching constructor cannot be found
102      * @throws IllegalAccessException if invocation is not permitted by security
103      * @throws InvocationTargetException if an error occurs on invocation
104      * @throws InstantiationException if an error occurs on instantiation
105      * @see Constructor#newInstance
106      */
107     public static <T> T invokeConstructor(final Class<T> cls, Object[] args, Class<?>[] parameterTypes)
108             throws NoSuchMethodException, IllegalAccessException, InvocationTargetException,
109             InstantiationException {
110         args = ArrayUtils.nullToEmpty(args);
111         parameterTypes = ArrayUtils.nullToEmpty(parameterTypes);
112         final Constructor<T> ctor = getMatchingAccessibleConstructor(cls, parameterTypes);
113         if (ctor == null) {
114             throw new NoSuchMethodException(
115                 "No such accessible constructor on object: " + cls.getName());
116         }
117         return ctor.newInstance(args);
118     }
119 
120     /**
121      * <p>Returns a new instance of the specified class inferring the right constructor
122      * from the types of the arguments.</p>
123      *
124      * <p>This locates and calls a constructor.
125      * The constructor signature must match the argument types exactly.</p>
126      *
127      * @param <T> the type to be constructed
128      * @param cls the class to be constructed, not {@code null}
129      * @param args the array of arguments, {@code null} treated as empty
130      * @return new instance of {@code cls}, not {@code null}
131      *
132      * @throws NullPointerException if {@code cls} is {@code null}
133      * @throws NoSuchMethodException if a matching constructor cannot be found
134      * @throws IllegalAccessException if invocation is not permitted by security
135      * @throws InvocationTargetException if an error occurs on invocation
136      * @throws InstantiationException if an error occurs on instantiation
137      * @see #invokeExactConstructor(java.lang.Class, java.lang.Object[], java.lang.Class[])
138      */
139     public static <T> T invokeExactConstructor(final Class<T> cls, Object... args)
140             throws NoSuchMethodException, IllegalAccessException, InvocationTargetException,
141             InstantiationException {
142         args = ArrayUtils.nullToEmpty(args);
143         final Class<?> parameterTypes[] = ClassUtils.toClass(args);
144         return invokeExactConstructor(cls, args, parameterTypes);
145     }
146 
147     /**
148      * <p>Returns a new instance of the specified class choosing the right constructor
149      * from the list of parameter types.</p>
150      *
151      * <p>This locates and calls a constructor.
152      * The constructor signature must match the parameter types exactly.</p>
153      *
154      * @param <T> the type to be constructed
155      * @param cls the class to be constructed, not {@code null}
156      * @param args the array of arguments, {@code null} treated as empty
157      * @param parameterTypes  the array of parameter types, {@code null} treated as empty
158      * @return new instance of <code>cls</code>, not {@code null}
159      *
160      * @throws NullPointerException if {@code cls} is {@code null}
161      * @throws NoSuchMethodException if a matching constructor cannot be found
162      * @throws IllegalAccessException if invocation is not permitted by security
163      * @throws InvocationTargetException if an error occurs on invocation
164      * @throws InstantiationException if an error occurs on instantiation
165      * @see Constructor#newInstance
166      */
167     public static <T> T invokeExactConstructor(final Class<T> cls, Object[] args,
168             Class<?>[] parameterTypes) throws NoSuchMethodException, IllegalAccessException,
169             InvocationTargetException, InstantiationException {
170         args = ArrayUtils.nullToEmpty(args);
171         parameterTypes = ArrayUtils.nullToEmpty(parameterTypes);
172         final Constructor<T> ctor = getAccessibleConstructor(cls, parameterTypes);
173         if (ctor == null) {
174             throw new NoSuchMethodException(
175                 "No such accessible constructor on object: "+ cls.getName());
176         }
177         return ctor.newInstance(args);
178     }
179 
180     //-----------------------------------------------------------------------
181     /**
182      * <p>Finds a constructor given a class and signature, checking accessibility.</p>
183      * 
184      * <p>This finds the constructor and ensures that it is accessible.
185      * The constructor signature must match the parameter types exactly.</p>
186      *
187      * @param <T> the constructor type
188      * @param cls the class to find a constructor for, not {@code null}
189      * @param parameterTypes the array of parameter types, {@code null} treated as empty
190      * @return the constructor, {@code null} if no matching accessible constructor found
191      * @see Class#getConstructor
192      * @see #getAccessibleConstructor(java.lang.reflect.Constructor)
193      * @throws NullPointerException if {@code cls} is {@code null}
194      */
195     public static <T> Constructor<T> getAccessibleConstructor(final Class<T> cls,
196             final Class<?>... parameterTypes) {
197         Validate.notNull(cls, "class cannot be null");
198         try {
199             return getAccessibleConstructor(cls.getConstructor(parameterTypes));
200         } catch (final NoSuchMethodException e) {
201             return null;
202         }
203     }
204 
205     /**
206      * <p>Checks if the specified constructor is accessible.</p>
207      * 
208      * <p>This simply ensures that the constructor is accessible.</p>
209      *
210      * @param <T> the constructor type
211      * @param ctor  the prototype constructor object, not {@code null}
212      * @return the constructor, {@code null} if no matching accessible constructor found
213      * @see java.lang.SecurityManager
214      * @throws NullPointerException if {@code ctor} is {@code null}
215      */
216     public static <T> Constructor<T> getAccessibleConstructor(final Constructor<T> ctor) {
217         Validate.notNull(ctor, "constructor cannot be null");
218         return MemberUtils.isAccessible(ctor)
219                 && isAccessible(ctor.getDeclaringClass()) ? ctor : null;
220     }
221 
222     /**
223      * <p>Finds an accessible constructor with compatible parameters.</p>
224      * 
225      * <p>This checks all the constructor and finds one with compatible parameters
226      * This requires that every parameter is assignable from the given parameter types.
227      * This is a more flexible search than the normal exact matching algorithm.</p>
228      *
229      * <p>First it checks if there is a constructor matching the exact signature.
230      * If not then all the constructors of the class are checked to see if their
231      * signatures are assignment-compatible with the parameter types.
232      * The first assignment-compatible matching constructor is returned.</p>
233      *
234      * @param <T> the constructor type
235      * @param cls  the class to find a constructor for, not {@code null}
236      * @param parameterTypes find method with compatible parameters
237      * @return the constructor, null if no matching accessible constructor found
238      * @throws NullPointerException if {@code cls} is {@code null}
239      */
240     public static <T> Constructor<T> getMatchingAccessibleConstructor(final Class<T> cls,
241             final Class<?>... parameterTypes) {
242         Validate.notNull(cls, "class cannot be null");
243         // see if we can find the constructor directly
244         // most of the time this works and it's much faster
245         try {
246             final Constructor<T> ctor = cls.getConstructor(parameterTypes);
247             MemberUtils.setAccessibleWorkaround(ctor);
248             return ctor;
249         } catch (final NoSuchMethodException e) { // NOPMD - Swallow
250         }
251         Constructor<T> result = null;
252         /*
253          * (1) Class.getConstructors() is documented to return Constructor<T> so as
254          * long as the array is not subsequently modified, everything's fine.
255          */
256         final Constructor<?>[] ctors = cls.getConstructors();
257 
258         // return best match:
259         for (Constructor<?> ctor : ctors) {
260             // compare parameters
261             if (ClassUtils.isAssignable(parameterTypes, ctor.getParameterTypes(), true)) {
262                 // get accessible version of constructor
263                 ctor = getAccessibleConstructor(ctor);
264                 if (ctor != null) {
265                     MemberUtils.setAccessibleWorkaround(ctor);
266                     if (result == null
267                             || MemberUtils.compareParameterTypes(ctor.getParameterTypes(), result
268                                     .getParameterTypes(), parameterTypes) < 0) {
269                         // temporary variable for annotation, see comment above (1)
270                         @SuppressWarnings("unchecked")
271                         final
272                         Constructor<T> constructor = (Constructor<T>)ctor;
273                         result = constructor;
274                     }
275                 }
276             }
277         }
278         return result;
279     }
280 
281     /**
282      * Learn whether the specified class is generally accessible, i.e. is
283      * declared in an entirely {@code public} manner.
284      * @param type to check
285      * @return {@code true} if {@code type} and any enclosing classes are
286      *         {@code public}.
287      */
288     private static boolean isAccessible(final Class<?> type) {
289         Class<?> cls = type;
290         while (cls != null) {
291             if (!Modifier.isPublic(cls.getModifiers())) {
292                 return false;
293             }
294             cls = cls.getEnclosingClass();
295         }
296         return true;
297     }
298 
299 }