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.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. If the parameter's name is
152 * defined in a class file, then that name will be returned by
153 * this method. Otherwise, this method will synthesize a name of
154 * the form argN, where N is the index of the parameter..
155 */
156 public String getName() {
157 // As per the spec, if a parameter has no name, return argX,
158 // where x is the index.
159 //
160 // Note: spec updates now outlaw empty strings as parameter
161 // names. The .equals("") is for compatibility with current
162 // JVM behavior. It may be removed at some point.
163 if(name == null || name.equals(""))
164 return "arg" + index;
165 else
166 return name;
167 }
168
169 /**
170 * Returns a {@code Type} object that identifies the parameterized
171 * type for the parameter represented by this {@code Parameter}
172 * object.
173 *
174 * @return a {@code Type} object identifying the parameterized
175 * type of the parameter represented by this object
176 */
177 public Type getParameterizedType() {
178 Type tmp = parameterTypeCache;
179 if (null == tmp) {
180 tmp = executable.getGenericParameterTypes()[index];
181 parameterTypeCache = tmp;
182 }
183
184 return tmp;
185 }
186
187 private transient volatile Type parameterTypeCache = null;
188
189 /**
190 * Returns a {@code Class} object that identifies the
191 * declared type for the parameter represented by this
192 * {@code Parameter} object.
193 *
194 * @return a {@code Class} object identifying the declared
195 * type of the parameter represented by this object
196 */
197 public Class<?> getType() {
198 Class<?> tmp = parameterClassCache;
199 if (null == tmp) {
200 tmp = executable.getParameterTypes()[index];
201 parameterClassCache = tmp;
202 }
203 return tmp;
204 }
205
206 private transient volatile Class<?> parameterClassCache = null;
207
208 /**
209 * Returns {@code true} if this parameter is implicitly declared
210 * in source code; returns {@code false} otherwise.
211 *
212 * @return true if and only if this parameter is implicitly
213 * declared as defined by <cite>The Java™ Language
214 * Specification</cite>.
215 */
216 public boolean isImplicit() {
217 return Modifier.isMandated(getModifiers());
218 }
219
220 /**
221 * Returns {@code true} if this parameter is neither implicitly
222 * nor explicitly declared in source code; returns {@code false}
223 * otherwise.
224 *
225 * @jls 13.1 The Form of a Binary
226 * @return true if and only if this parameter is a synthetic
227 * construct as defined by
228 * <cite>The Java™ Language Specification</cite>.
229 */
230 public boolean isSynthetic() {
231 return Modifier.isSynthetic(getModifiers());
232 }
233
234 /**
235 * Returns {@code true} if this parameter represents a variable
236 * argument list; returns {@code false} otherwise.
237 *
238 * @return {@code true} if an only if this parameter represents a
239 * variable argument list.
240 */
241 public boolean isVarArgs() {
242 return executable.isVarArgs() &&
243 index == executable.getParameterCount() - 1;
244 }
245
246
247 /**
248 * {@inheritDoc}
249 * @throws NullPointerException {@inheritDoc}
250 */
251 public <T extends Annotation> T getAnnotation(Class<T> annotationClass) {
252 Objects.requireNonNull(annotationClass);
253 return annotationClass.cast(declaredAnnotations().get(annotationClass));
254 }
255
256 /**
257 * {@inheritDoc}
258 * @throws NullPointerException {@inheritDoc}
259 */
260 @Override
261 public <T extends Annotation> T[] getAnnotationsByType(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 @Override
288 public <T extends Annotation> T[] getDeclaredAnnotationsByType(Class<T> annotationClass) {
289 // Only annotations on classes are inherited, for all other
290 // objects getDeclaredAnnotations is the same as
291 // getAnnotations.
292 return getAnnotationsByType(annotationClass);
293 }
294
295 /**
296 * {@inheritDoc}
297 */
298 public Annotation[] getAnnotations() {
299 return getDeclaredAnnotations();
300 }
301
302 private transient Map<Class<? extends Annotation>, Annotation> declaredAnnotations;
303
304 private synchronized Map<Class<? extends Annotation>, Annotation> declaredAnnotations() {
305 if(null == declaredAnnotations) {
306 declaredAnnotations =
307 new HashMap<Class<? extends Annotation>, Annotation>();
308 Annotation[] ann = getDeclaredAnnotations();
309 for(int i = 0; i < ann.length; i++)
310 declaredAnnotations.put(ann[i].annotationType(), ann[i]);
311 }
312 return declaredAnnotations;
313 }
314
315 }