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™ 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 instanceof Class)? 114 Field.getTypeName((Class)type): 115 (type.toString()); 116 117 sb.append(Modifier.toString(getModifiers())); 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™ 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™ 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 public <T extends Annotation> T[] getAnnotations(Class<T> annotationClass) { 262 Objects.requireNonNull(annotationClass); 263 264 return AnnotationSupport.getMultipleAnnotations(declaredAnnotations(), annotationClass); 265 } 266 267 /** 268 * {@inheritDoc} 269 */ 270 public Annotation[] getDeclaredAnnotations() { 271 return executable.getParameterAnnotations()[index]; 272 } 273 274 /** 275 * @throws NullPointerException {@inheritDoc} 276 */ 277 public <T extends Annotation> T getDeclaredAnnotation(Class<T> annotationClass) { 278 // Only annotations on classes are inherited, for all other 279 // objects getDeclaredAnnotation is the same as 280 // getAnnotation. 281 return getAnnotation(annotationClass); 282 } 283 284 /** 285 * @throws NullPointerException {@inheritDoc} 286 */ 287 public <T extends Annotation> T[] getDeclaredAnnotations(Class<T> annotationClass) { 288 // Only annotations on classes are inherited, for all other 289 // objects getDeclaredAnnotations is the same as 290 // getAnnotations. 291 return getAnnotations(annotationClass); 292 } 293 294 /** 295 * {@inheritDoc} 296 */ 297 public Annotation[] getAnnotations() { 298 return getDeclaredAnnotations(); 299 } 300 301 /** 302 * @throws NullPointerException {@inheritDoc} 303 */ 304 public boolean isAnnotationPresent( 305 Class<? extends Annotation> annotationClass) { 306 return getAnnotation(annotationClass) != null; 307 } 308 309 private transient Map<Class<? extends Annotation>, Annotation> declaredAnnotations; 310 311 private synchronized Map<Class<? extends Annotation>, Annotation> declaredAnnotations() { 312 if(null == declaredAnnotations) { 313 declaredAnnotations = 314 new HashMap<Class<? extends Annotation>, Annotation>(); 315 Annotation[] ann = getDeclaredAnnotations(); 316 for(int i = 0; i < ann.length; i++) 317 declaredAnnotations.put(ann[i].annotationType(), ann[i]); 318 } 319 return declaredAnnotations; 320 } 321 322 }