1 /*
   2  * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 package java.lang.reflect;
  26 
  27 import java.lang.annotation.*;
  28 import java.util.HashMap;
  29 import java.util.Map;
  30 import java.util.Objects;
  31 import sun.reflect.annotation.AnnotationSupport;
  32 
  33 /**
  34  * Information about method parameters.
  35  *
  36  * A {@code Parameter} provides information about method parameters,
  37  * including its name and modifiers.  It also provides an alternate
  38  * means of obtaining attributes for the parameter.
  39  *
  40  * @since 1.8
  41  */
  42 public final class Parameter implements AnnotatedElement {
  43 
  44     private final String name;
  45     private final int modifiers;
  46     private final Executable executable;
  47     private final int index;
  48 
  49     /**
  50      * Package-private constructor for {@code Parameter}.
  51      *
  52      * If method parameter data is present in the classfile, then the
  53      * JVM creates {@code Parameter} objects directly.  If it is
  54      * absent, however, then {@code Executable} uses this constructor
  55      * to synthesize them.
  56      *
  57      * @param name The name of the parameter.
  58      * @param modifiers The modifier flags for the parameter.
  59      * @param executable The executable which defines this parameter.
  60      * @param index The index of the parameter.
  61      */
  62     Parameter(String name,
  63               int modifiers,
  64               Executable executable,
  65               int index) {
  66         this.name = name;
  67         this.modifiers = modifiers;
  68         this.executable = executable;
  69         this.index = index;
  70     }
  71 
  72     /**
  73      * Compares based on the executable and the index.
  74      *
  75      * @param obj The object to compare.
  76      * @return Whether or not this is equal to the argument.
  77      */
  78     public boolean equals(Object obj) {
  79         if(obj instanceof Parameter) {
  80             Parameter other = (Parameter)obj;
  81             return (other.executable.equals(executable) &&
  82                     other.index == index);
  83         }
  84         return false;
  85     }
  86 
  87     /**
  88      * Returns a hash code based on the executable's hash code and the
  89      * index.
  90      *
  91      * @return A hash code based on the executable's hash code.
  92      */
  93     public int hashCode() {
  94         return executable.hashCode() ^ index;
  95     }
  96 
  97     /**
  98      * Returns a string describing this parameter.  The format is the
  99      * modifiers for the parameter, if any, in canonical order as
 100      * recommended by <cite>The Java&trade; Language
 101      * Specification</cite>, followed by the fully- qualified type of
 102      * the parameter (excluding the last [] if the parameter is
 103      * variable arity), followed by "..." if the parameter is variable
 104      * arity, followed by a space, followed by the name of the
 105      * parameter.
 106      *
 107      * @return A string representation of the parameter and associated
 108      * information.
 109      */
 110     public String toString() {
 111         final StringBuilder sb = new StringBuilder();
 112         final Type type = getParameterizedType();
 113         final String typename = type.getTypeName();
 114 
 115         sb.append(Modifier.toString(getModifiers()));
 116 
 117         if(0 != modifiers)
 118             sb.append(' ');
 119 
 120         if(isVarArgs())
 121             sb.append(typename.replaceFirst("\\[\\]$", "..."));
 122         else
 123             sb.append(typename);
 124 
 125         sb.append(' ');
 126         sb.append(getName());
 127 
 128         return sb.toString();
 129     }
 130 
 131     /**
 132      * Return the {@code Executable} which declares this parameter.
 133      *
 134      * @return The {@code Executable} declaring this parameter.
 135      */
 136     public Executable getDeclaringExecutable() {
 137         return executable;
 138     }
 139 
 140     /**
 141      * Get the modifier flags for this the parameter represented by
 142      * this {@code Parameter} object.
 143      *
 144      * @return The modifier flags for this parameter.
 145      */
 146     public int getModifiers() {
 147         return modifiers;
 148     }
 149 
 150     /**
 151      * Returns the name of the parameter.  The names of the parameters
 152      * of a single executable must all the be distinct.  When names
 153      * from the originating source are available, they are returned.
 154      * Otherwise, an implementation of this method is free to create a
 155      * name of this parameter, subject to the unquiness requirments.
 156      */
 157     public String getName() {
 158         // As per the spec, if a parameter has no name, return argX,
 159         // where x is the index.
 160         //
 161         // Note: spec updates now outlaw empty strings as parameter
 162         // names.  The .equals("") is for compatibility with current
 163         // JVM behavior.  It may be removed at some point.
 164         if(name == null || name.equals(""))
 165             return "arg" + index;
 166         else
 167             return name;
 168     }
 169 
 170     /**
 171      * Returns a {@code Type} object that identifies the parameterized
 172      * type for the parameter represented by this {@code Parameter}
 173      * object.
 174      *
 175      * @return a {@code Type} object identifying the parameterized
 176      * type of the parameter represented by this object
 177      */
 178     public Type getParameterizedType() {
 179         Type tmp = parameterTypeCache;
 180         if (null == tmp) {
 181             tmp = executable.getGenericParameterTypes()[index];
 182             parameterTypeCache = tmp;
 183         }
 184 
 185         return tmp;
 186     }
 187 
 188     private transient volatile Type parameterTypeCache = null;
 189 
 190     /**
 191      * Returns a {@code Class} object that identifies the
 192      * declared type for the parameter represented by this
 193      * {@code Parameter} object.
 194      *
 195      * @return a {@code Class} object identifying the declared
 196      * type of the parameter represented by this object
 197      */
 198     public Class<?> getType() {
 199         Class<?> tmp = parameterClassCache;
 200         if (null == tmp) {
 201             tmp = executable.getParameterTypes()[index];
 202             parameterClassCache = tmp;
 203         }
 204         return tmp;
 205     }
 206 
 207     private transient volatile Class<?> parameterClassCache = null;
 208 
 209     /**
 210      * Returns {@code true} if this parameter is implicitly declared
 211      * in source code; returns {@code false} otherwise.
 212      *
 213      * @return true if and only if this parameter is implicitly
 214      * declared as defined by <cite>The Java&trade; Language
 215      * Specification</cite>.
 216      */
 217     public boolean isImplicit() {
 218         return Modifier.isMandated(getModifiers());
 219     }
 220 
 221     /**
 222      * Returns {@code true} if this parameter is neither implicitly
 223      * nor explicitly declared in source code; returns {@code false}
 224      * otherwise.
 225      *
 226      * @jls 13.1 The Form of a Binary
 227      * @return true if and only if this parameter is a synthetic
 228      * construct as defined by
 229      * <cite>The Java&trade; Language Specification</cite>.
 230      */
 231     public boolean isSynthetic() {
 232         return Modifier.isSynthetic(getModifiers());
 233     }
 234 
 235     /**
 236      * Returns {@code true} if this parameter represents a variable
 237      * argument list; returns {@code false} otherwise.
 238      *
 239      * @return {@code true} if an only if this parameter represents a
 240      * variable argument list.
 241      */
 242     public boolean isVarArgs() {
 243         return executable.isVarArgs() &&
 244             index == executable.getParameterCount() - 1;
 245     }
 246 
 247 
 248     /**
 249      * {@inheritDoc}
 250      * @throws NullPointerException {@inheritDoc}
 251      */
 252     public <T extends Annotation> T getAnnotation(Class<T> annotationClass) {
 253         Objects.requireNonNull(annotationClass);
 254         return annotationClass.cast(declaredAnnotations().get(annotationClass));
 255     }
 256 
 257     /**
 258      * {@inheritDoc}
 259      * @throws NullPointerException {@inheritDoc}
 260      */
 261     @Override
 262     public <T extends Annotation> T[] getAnnotationsByType(Class<T> annotationClass) {
 263         Objects.requireNonNull(annotationClass);
 264 
 265         return AnnotationSupport.getMultipleAnnotations(declaredAnnotations(), annotationClass);
 266     }
 267 
 268     /**
 269      * {@inheritDoc}
 270      */
 271     public Annotation[] getDeclaredAnnotations() {
 272         return executable.getParameterAnnotations()[index];
 273     }
 274 
 275     /**
 276      * @throws NullPointerException {@inheritDoc}
 277      */
 278     public <T extends Annotation> T getDeclaredAnnotation(Class<T> annotationClass) {
 279         // Only annotations on classes are inherited, for all other
 280         // objects getDeclaredAnnotation is the same as
 281         // getAnnotation.
 282         return getAnnotation(annotationClass);
 283     }
 284 
 285     /**
 286      * @throws NullPointerException {@inheritDoc}
 287      */
 288     @Override
 289     public <T extends Annotation> T[] getDeclaredAnnotationsByType(Class<T> annotationClass) {
 290         // Only annotations on classes are inherited, for all other
 291         // objects getDeclaredAnnotations is the same as
 292         // getAnnotations.
 293         return getAnnotationsByType(annotationClass);
 294     }
 295 
 296     /**
 297      * {@inheritDoc}
 298      */
 299     public Annotation[] getAnnotations() {
 300         return getDeclaredAnnotations();
 301     }
 302 
 303     private transient Map<Class<? extends Annotation>, Annotation> declaredAnnotations;
 304 
 305     private synchronized Map<Class<? extends Annotation>, Annotation> declaredAnnotations() {
 306         if(null == declaredAnnotations) {
 307             declaredAnnotations =
 308                 new HashMap<Class<? extends Annotation>, Annotation>();
 309             Annotation[] ann = getDeclaredAnnotations();
 310             for(int i = 0; i < ann.length; i++)
 311                 declaredAnnotations.put(ann[i].annotationType(), ann[i]);
 312         }
 313         return declaredAnnotations;
 314     }
 315 
 316 }