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())); 118 119 if(0 != modifiers) 120 sb.append(" "); 121 122 if(isVarArgs()) 123 sb.append(typename.replaceFirst("\\[\\]$", "...")); 124 else 125 sb.append(typename); 126 127 sb.append(" "); 128 sb.append(getName()); 129 130 return sb.toString(); 131 } 132 133 /** 134 * Return the {@code Executable} which declares this parameter. 135 * 136 * @return The {@code Executable} declaring this parameter. 137 */ 138 public Executable getDeclaringExecutable() { 139 return executable; 140 } 141 142 /** 143 * Get the modifier flags for this the parameter represented by 144 * this {@code Parameter} object. 145 * 146 * @return The modifier flags for this parameter. 147 */ 148 public int getModifiers() { 149 return modifiers; 150 } 151 152 /** 153 * Returns the name of the parameter. The names of the parameters 154 * of a single executable must all the be distinct. When names 155 * from the originating source are available, they are returned. 156 * Otherwise, an implementation of this method is free to create a 157 * name of this parameter, subject to the unquiness requirments. 158 */ 159 public String getName() { 160 // As per the spec, if a parameter has no name, return argX, 161 // where x is the index. 162 // 163 // Note: spec updates now outlaw empty strings as parameter 164 // names. The .equals("") is for compatibility with current 165 // JVM behavior. It may be removed at some point. 166 if(name == null || name.equals("")) 167 return "arg" + index; 168 else 169 return name; 170 } 171 172 /** 173 * Returns a {@code Type} object that identifies the parameterized 174 * type for the parameter represented by this {@code Parameter} 175 * object. 176 * 177 * @return a {@code Type} object identifying the parameterized 178 * type of the parameter represented by this object 179 */ 180 public Type getParameterizedType() { 181 Type tmp = parameterTypeCache; 182 if (null == tmp) { 183 tmp = executable.getGenericParameterTypes()[index]; 184 parameterTypeCache = tmp; 185 } 186 187 return tmp; 188 } 189 190 private transient volatile Type parameterTypeCache = null; 191 192 /** 193 * Returns a {@code Class} object that identifies the 194 * declared type for the parameter represented by this 195 * {@code Parameter} object. 196 * 197 * @return a {@code Class} object identifying the declared 198 * type of the parameter represented by this object 199 */ 200 public Class<?> getType() { 201 Class<?> tmp = parameterClassCache; 202 if (null == tmp) { 203 tmp = executable.getParameterTypes()[index]; 204 parameterClassCache = tmp; 205 } 206 return tmp; 207 } 208 209 private transient volatile Class<?> parameterClassCache = null; 210 211 /** 212 * Returns {@code true} if this parameter is implicitly declared 213 * in source code; returns {@code false} otherwise. 214 * 215 * @return true if and only if this parameter is implicitly 216 * declared as defined by <cite>The Java™ Language 217 * Specification</cite>. 218 */ 219 public boolean isImplicit() { 220 return Modifier.isMandated(getModifiers()); 221 } 222 223 /** 224 * Returns {@code true} if this parameter is neither implicitly 225 * nor explicitly declared in source code; returns {@code false} 226 * otherwise. 227 * 228 * @jls 13.1 The Form of a Binary 229 * @return true if and only if this parameter is a synthetic 230 * construct as defined by 231 * <cite>The Java™ Language Specification</cite>. 232 */ 233 public boolean isSynthetic() { 234 return Modifier.isSynthetic(getModifiers()); 235 } 236 237 /** 238 * Returns {@code true} if this parameter represents a variable 239 * argument list; returns {@code false} otherwise. 240 * 241 * @return {@code true} if an only if this parameter represents a 242 * variable argument list. 243 */ 244 public boolean isVarArgs() { 245 return executable.isVarArgs() && 246 index == executable.getParameterCount() - 1; 247 } 248 249 250 /** 251 * {@inheritDoc} 252 * @throws NullPointerException {@inheritDoc} 253 */ 254 public <T extends Annotation> T getAnnotation(Class<T> annotationClass) { 255 Objects.requireNonNull(annotationClass); 256 return annotationClass.cast(declaredAnnotations().get(annotationClass)); 257 } 258 259 /** 260 * {@inheritDoc} 261 * @throws NullPointerException {@inheritDoc} 262 */ 263 @Override 264 public <T extends Annotation> T[] getAnnotationsByType(Class<T> annotationClass) { 265 Objects.requireNonNull(annotationClass); 266 267 return AnnotationSupport.getMultipleAnnotations(declaredAnnotations(), annotationClass); 268 } 269 270 /** 271 * {@inheritDoc} 272 */ 273 public Annotation[] getDeclaredAnnotations() { 274 return executable.getParameterAnnotations()[index]; 275 } 276 277 /** 278 * @throws NullPointerException {@inheritDoc} 279 */ 280 public <T extends Annotation> T getDeclaredAnnotation(Class<T> annotationClass) { 281 // Only annotations on classes are inherited, for all other 282 // objects getDeclaredAnnotation is the same as 283 // getAnnotation. 284 return getAnnotation(annotationClass); 285 } 286 287 /** 288 * @throws NullPointerException {@inheritDoc} 289 */ 290 @Override 291 public <T extends Annotation> T[] getDeclaredAnnotationsByType(Class<T> annotationClass) { 292 // Only annotations on classes are inherited, for all other 293 // objects getDeclaredAnnotations is the same as 294 // getAnnotations. 295 return getAnnotationsByType(annotationClass); 296 } 297 298 /** 299 * {@inheritDoc} 300 */ 301 public Annotation[] getAnnotations() { 302 return getDeclaredAnnotations(); 303 } 304 305 private transient Map<Class<? extends Annotation>, Annotation> declaredAnnotations; 306 307 private synchronized Map<Class<? extends Annotation>, Annotation> declaredAnnotations() { 308 if(null == declaredAnnotations) { 309 declaredAnnotations = 310 new HashMap<Class<? extends Annotation>, Annotation>(); 311 Annotation[] ann = getDeclaredAnnotations(); 312 for(int i = 0; i < ann.length; i++) 313 declaredAnnotations.put(ann[i].annotationType(), ann[i]); 314 } 315 return declaredAnnotations; 316 } 317 318 }