Coverage Report - org.apache.commons.lang3.reflect.ConstructorUtils
 
Classes in this File Line Coverage Branch Coverage Complexity
ConstructorUtils
92%
50/54
87%
21/24
3,111
 
 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  0
         super();
 58  0
     }
 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  14
         args = ArrayUtils.nullToEmpty(args);
 83  14
         final Class<?> parameterTypes[] = ClassUtils.toClass(args);
 84  14
         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  14
         args = ArrayUtils.nullToEmpty(args);
 111  14
         parameterTypes = ArrayUtils.nullToEmpty(parameterTypes);
 112  14
         final Constructor<T> ctor = getMatchingAccessibleConstructor(cls, parameterTypes);
 113  14
         if (ctor == null) {
 114  0
             throw new NoSuchMethodException(
 115  0
                 "No such accessible constructor on object: " + cls.getName());
 116  
         }
 117  14
         if (ctor.isVarArgs()) {
 118  3
             Class<?>[] methodParameterTypes = ctor.getParameterTypes();
 119  3
             args = MethodUtils.getVarArgs(args, methodParameterTypes);
 120  
         }
 121  14
         return ctor.newInstance(args);
 122  
     }
 123  
 
 124  
     /**
 125  
      * <p>Returns a new instance of the specified class inferring the right constructor
 126  
      * from the types of the arguments.</p>
 127  
      *
 128  
      * <p>This locates and calls a constructor.
 129  
      * The constructor signature must match the argument types exactly.</p>
 130  
      *
 131  
      * @param <T> the type to be constructed
 132  
      * @param cls the class to be constructed, not {@code null}
 133  
      * @param args the array of arguments, {@code null} treated as empty
 134  
      * @return new instance of {@code cls}, not {@code null}
 135  
      *
 136  
      * @throws NullPointerException if {@code cls} is {@code null}
 137  
      * @throws NoSuchMethodException if a matching constructor cannot be found
 138  
      * @throws IllegalAccessException if invocation is not permitted by security
 139  
      * @throws InvocationTargetException if an error occurs on invocation
 140  
      * @throws InstantiationException if an error occurs on instantiation
 141  
      * @see #invokeExactConstructor(java.lang.Class, java.lang.Object[], java.lang.Class[])
 142  
      */
 143  
     public static <T> T invokeExactConstructor(final Class<T> cls, Object... args)
 144  
             throws NoSuchMethodException, IllegalAccessException, InvocationTargetException,
 145  
             InstantiationException {
 146  8
         args = ArrayUtils.nullToEmpty(args);
 147  8
         final Class<?> parameterTypes[] = ClassUtils.toClass(args);
 148  8
         return invokeExactConstructor(cls, args, parameterTypes);
 149  
     }
 150  
 
 151  
     /**
 152  
      * <p>Returns a new instance of the specified class choosing the right constructor
 153  
      * from the list of parameter types.</p>
 154  
      *
 155  
      * <p>This locates and calls a constructor.
 156  
      * The constructor signature must match the parameter types exactly.</p>
 157  
      *
 158  
      * @param <T> the type to be constructed
 159  
      * @param cls the class to be constructed, not {@code null}
 160  
      * @param args the array of arguments, {@code null} treated as empty
 161  
      * @param parameterTypes  the array of parameter types, {@code null} treated as empty
 162  
      * @return new instance of <code>cls</code>, not {@code null}
 163  
      *
 164  
      * @throws NullPointerException if {@code cls} is {@code null}
 165  
      * @throws NoSuchMethodException if a matching constructor cannot be found
 166  
      * @throws IllegalAccessException if invocation is not permitted by security
 167  
      * @throws InvocationTargetException if an error occurs on invocation
 168  
      * @throws InstantiationException if an error occurs on instantiation
 169  
      * @see Constructor#newInstance
 170  
      */
 171  
     public static <T> T invokeExactConstructor(final Class<T> cls, Object[] args,
 172  
             Class<?>[] parameterTypes) throws NoSuchMethodException, IllegalAccessException,
 173  
             InvocationTargetException, InstantiationException {
 174  9
         args = ArrayUtils.nullToEmpty(args);
 175  9
         parameterTypes = ArrayUtils.nullToEmpty(parameterTypes);
 176  9
         final Constructor<T> ctor = getAccessibleConstructor(cls, parameterTypes);
 177  9
         if (ctor == null) {
 178  3
             throw new NoSuchMethodException(
 179  3
                 "No such accessible constructor on object: "+ cls.getName());
 180  
         }
 181  6
         return ctor.newInstance(args);
 182  
     }
 183  
 
 184  
     //-----------------------------------------------------------------------
 185  
     /**
 186  
      * <p>Finds a constructor given a class and signature, checking accessibility.</p>
 187  
      * 
 188  
      * <p>This finds the constructor and ensures that it is accessible.
 189  
      * The constructor signature must match the parameter types exactly.</p>
 190  
      *
 191  
      * @param <T> the constructor type
 192  
      * @param cls the class to find a constructor for, not {@code null}
 193  
      * @param parameterTypes the array of parameter types, {@code null} treated as empty
 194  
      * @return the constructor, {@code null} if no matching accessible constructor found
 195  
      * @see Class#getConstructor
 196  
      * @see #getAccessibleConstructor(java.lang.reflect.Constructor)
 197  
      * @throws NullPointerException if {@code cls} is {@code null}
 198  
      */
 199  
     public static <T> Constructor<T> getAccessibleConstructor(final Class<T> cls,
 200  
             final Class<?>... parameterTypes) {
 201  12
         Validate.notNull(cls, "class cannot be null");
 202  
         try {
 203  12
             return getAccessibleConstructor(cls.getConstructor(parameterTypes));
 204  3
         } catch (final NoSuchMethodException e) {
 205  3
             return null;
 206  
         }
 207  
     }
 208  
 
 209  
     /**
 210  
      * <p>Checks if the specified constructor is accessible.</p>
 211  
      * 
 212  
      * <p>This simply ensures that the constructor is accessible.</p>
 213  
      *
 214  
      * @param <T> the constructor type
 215  
      * @param ctor  the prototype constructor object, not {@code null}
 216  
      * @return the constructor, {@code null} if no matching accessible constructor found
 217  
      * @see java.lang.SecurityManager
 218  
      * @throws NullPointerException if {@code ctor} is {@code null}
 219  
      */
 220  
     public static <T> Constructor<T> getAccessibleConstructor(final Constructor<T> ctor) {
 221  52
         Validate.notNull(ctor, "constructor cannot be null");
 222  104
         return MemberUtils.isAccessible(ctor)
 223  52
                 && isAccessible(ctor.getDeclaringClass()) ? ctor : null;
 224  
     }
 225  
 
 226  
     /**
 227  
      * <p>Finds an accessible constructor with compatible parameters.</p>
 228  
      * 
 229  
      * <p>This checks all the constructor and finds one with compatible parameters
 230  
      * This requires that every parameter is assignable from the given parameter types.
 231  
      * This is a more flexible search than the normal exact matching algorithm.</p>
 232  
      *
 233  
      * <p>First it checks if there is a constructor matching the exact signature.
 234  
      * If not then all the constructors of the class are checked to see if their
 235  
      * signatures are assignment-compatible with the parameter types.
 236  
      * The first assignment-compatible matching constructor is returned.</p>
 237  
      *
 238  
      * @param <T> the constructor type
 239  
      * @param cls  the class to find a constructor for, not {@code null}
 240  
      * @param parameterTypes find method with compatible parameters
 241  
      * @return the constructor, null if no matching accessible constructor found
 242  
      * @throws NullPointerException if {@code cls} is {@code null}
 243  
      */
 244  
     public static <T> Constructor<T> getMatchingAccessibleConstructor(final Class<T> cls,
 245  
             final Class<?>... parameterTypes) {
 246  34
         Validate.notNull(cls, "class cannot be null");
 247  
         // see if we can find the constructor directly
 248  
         // most of the time this works and it's much faster
 249  
         try {
 250  34
             final Constructor<T> ctor = cls.getConstructor(parameterTypes);
 251  14
             MemberUtils.setAccessibleWorkaround(ctor);
 252  14
             return ctor;
 253  20
         } catch (final NoSuchMethodException e) { // NOPMD - Swallow
 254  
         }
 255  20
         Constructor<T> result = null;
 256  
         /*
 257  
          * (1) Class.getConstructors() is documented to return Constructor<T> so as
 258  
          * long as the array is not subsequently modified, everything's fine.
 259  
          */
 260  20
         final Constructor<?>[] ctors = cls.getConstructors();
 261  
 
 262  
         // return best match:
 263  193
         for (Constructor<?> ctor : ctors) {
 264  
             // compare parameters
 265  173
             if (MemberUtils.isMatchingConstructor(ctor, parameterTypes)) {
 266  
                 // get accessible version of constructor
 267  41
                 ctor = getAccessibleConstructor(ctor);
 268  41
                 if (ctor != null) {
 269  41
                     MemberUtils.setAccessibleWorkaround(ctor);
 270  41
                     if (result == null || MemberUtils.compareConstructorFit(ctor, result, parameterTypes) < 0) {
 271  
                         // temporary variable for annotation, see comment above (1)
 272  
                         @SuppressWarnings("unchecked")
 273  
                         final
 274  34
                         Constructor<T> constructor = (Constructor<T>)ctor;
 275  34
                         result = constructor;
 276  
                     }
 277  
                 }
 278  
             }
 279  
         }
 280  20
         return result;
 281  
     }
 282  
 
 283  
     /**
 284  
      * Learn whether the specified class is generally accessible, i.e. is
 285  
      * declared in an entirely {@code public} manner.
 286  
      * @param type to check
 287  
      * @return {@code true} if {@code type} and any enclosing classes are
 288  
      *         {@code public}.
 289  
      */
 290  
     private static boolean isAccessible(final Class<?> type) {
 291  52
         Class<?> cls = type;
 292  148
         while (cls != null) {
 293  99
             if (!Modifier.isPublic(cls.getModifiers())) {
 294  3
                 return false;
 295  
             }
 296  96
             cls = cls.getEnclosingClass();
 297  
         }
 298  49
         return true;
 299  
     }
 300  
 
 301  
 }