1 /*
2 * Copyright (c) 2018, 2019, 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
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23 * questions.
24 */
25 package java.lang.constant;
26
27 import java.lang.invoke.TypeDescriptor;
28 import java.util.stream.Stream;
29
30 import sun.invoke.util.Wrapper;
31
32 import static java.lang.constant.ConstantUtils.binaryToInternal;
33 import static java.lang.constant.ConstantUtils.dropLastChar;
34 import static java.lang.constant.ConstantUtils.internalToBinary;
35 import static java.lang.constant.ConstantUtils.validateMemberName;
36 import static java.util.Objects.requireNonNull;
37 import static java.util.stream.Collectors.joining;
38
39 /**
40 * A <a href="package-summary.html#nominal">nominal descriptor</a> for a
41 * {@link Class} constant.
42 *
43 * <p>For common system types, including all the primitive types, there are
44 * predefined {@linkplain ClassDesc} constants in {@link ConstantDescs}.
45 * (The {@code java.lang.constant} APIs consider {@code void} to be a primitive type.)
46 * To create a {@linkplain ClassDesc} for a class or interface type, use {@link #of} or
47 * {@link #ofDescriptor(String)}; to create a {@linkplain ClassDesc} for an array
48 * type, use {@link #ofDescriptor(String)}, or first obtain a
49 * {@linkplain ClassDesc} for the component type and then call the {@link #arrayType()}
50 * or {@link #arrayType(int)} methods.
51 *
52 * @apiNote In the future, if the Java language permits, {@linkplain ClassDesc}
53 * may become a {@code sealed} interface, which would prohibit subclassing except
54 * by explicitly permitted types. Non-platform classes should not implement
55 * {@linkplain ClassDesc} directly.
56 *
57 * @see ConstantDescs
58 *
59 * @since 12
60 */
61 public interface ClassDesc
62 extends ConstantDesc,
63 TypeDescriptor.OfField<ClassDesc> {
64
65 /**
66 * Returns a {@linkplain ClassDesc} for a class or interface type,
67 * given the name of the class or interface, such as {@code "java.lang.String"}.
68 * (To create a descriptor for an array type, either use {@link #ofDescriptor(String)}
69 * or {@link #arrayType()}; to create a descriptor for a primitive type, use
70 * {@link #ofDescriptor(String)} or use the predefined constants in
71 * {@link ConstantDescs}).
72 *
73 * @param name the fully qualified (dot-separated) binary class name
74 * @return a {@linkplain ClassDesc} describing the desired class
75 * @throws NullPointerException if any argument is {@code null}
76 * @throws IllegalArgumentException if the name string is not in the
77 * correct format
78 */
79 static ClassDesc of(String name) {
80 ConstantUtils.validateBinaryClassName(requireNonNull(name));
81 return ClassDesc.ofDescriptor("L" + binaryToInternal(name) + ";");
82 }
83
84 /**
85 * Returns a {@linkplain ClassDesc} for a class or interface type,
86 * given a package name and the unqualified (simple) name for the
87 * class or interface.
88 *
89 * @param packageName the package name (dot-separated); if the package
90 * name is the empty string, the class is considered to
91 * be in the unnamed package
92 * @param className the unqualified (simple) class name
93 * @return a {@linkplain ClassDesc} describing the desired class
94 * @throws NullPointerException if any argument is {@code null}
95 * @throws IllegalArgumentException if the package name or class name are
96 * not in the correct format
97 */
98 static ClassDesc of(String packageName, String className) {
99 ConstantUtils.validateBinaryClassName(requireNonNull(packageName));
100 if (packageName.isEmpty()) {
101 return of(className);
102 }
103 validateMemberName(requireNonNull(className), false);
104 return ofDescriptor("L" + binaryToInternal(packageName) +
105 (packageName.length() > 0 ? "/" : "") + className + ";");
106 }
107
108 /**
109 * Returns a {@linkplain ClassDesc} given a descriptor string for a class,
110 * interface, array, or primitive type.
111 *
112 * @apiNote
113 *
114 * A field type descriptor string for a non-array type is either
115 * a one-letter code corresponding to a primitive type
116 * ({@code "J", "I", "C", "S", "B", "D", "F", "Z", "V"}), or the letter {@code "L"}, followed
117 * by the fully qualified binary name of a class, followed by {@code ";"}.
118 * A field type descriptor for an array type is the character {@code "["}
119 * followed by the field descriptor for the component type. Examples of
120 * valid type descriptor strings include {@code "Ljava/lang/String;"}, {@code "I"},
121 * {@code "[I"}, {@code "V"}, {@code "[Ljava/lang/String;"}, etc.
122 * See JVMS 4.3.2 ("Field Descriptors") for more detail.
123 *
124 * @param descriptor a field descriptor string
125 * @return a {@linkplain ClassDesc} describing the desired class
126 * @throws NullPointerException if any argument is {@code null}
127 * @throws IllegalArgumentException if the name string is not in the
128 * correct format
129 * @jvms 4.3.2 Field Descriptors
130 * @jvms 4.4.1 The CONSTANT_Class_info Structure
131 */
132 static ClassDesc ofDescriptor(String descriptor) {
133 requireNonNull(descriptor);
134 if (descriptor.isEmpty()) {
135 throw new IllegalArgumentException(
136 "not a valid reference type descriptor: " + descriptor);
137 }
138 int depth = ConstantUtils.arrayDepth(descriptor);
139 if (depth > ConstantUtils.MAX_ARRAY_TYPE_DESC_DIMENSIONS) {
140 throw new IllegalArgumentException(
141 "Cannot create an array type descriptor with more than " +
142 ConstantUtils.MAX_ARRAY_TYPE_DESC_DIMENSIONS + " dimensions");
143 }
144 return (descriptor.length() == 1)
145 ? new PrimitiveClassDescImpl(descriptor)
146 : new ReferenceClassDescImpl(descriptor);
147 }
148
149 /**
150 * Returns a {@linkplain ClassDesc} for an array type whose component type
151 * is described by this {@linkplain ClassDesc}.
152 *
153 * @return a {@linkplain ClassDesc} describing the array type
154 * @throws IllegalStateException if the resulting {@linkplain ClassDesc} would have an array rank of greater than 255
155 * @jvms 4.4.1 The CONSTANT_Class_info Structure
156 */
157 default ClassDesc arrayType() {
158 int depth = ConstantUtils.arrayDepth(descriptorString());
159 if (depth >= ConstantUtils.MAX_ARRAY_TYPE_DESC_DIMENSIONS) {
160 throw new IllegalStateException(
161 "Cannot create an array type descriptor with more than " +
162 ConstantUtils.MAX_ARRAY_TYPE_DESC_DIMENSIONS + " dimensions");
163 }
164 return arrayType(1);
165 }
166
167 /**
168 * Returns a {@linkplain ClassDesc} for an array type of the specified rank,
169 * whose component type is described by this {@linkplain ClassDesc}.
170 *
171 * @param rank the rank of the array
172 * @return a {@linkplain ClassDesc} describing the array type
173 * @throws IllegalArgumentException if the rank is less than or equal to zero or if the rank of the resulting array type is
174 * greater than 255
175 * @jvms 4.4.1 The CONSTANT_Class_info Structure
176 */
177 default ClassDesc arrayType(int rank) {
178 int currentDepth = ConstantUtils.arrayDepth(descriptorString());
179 if (rank <= 0 || currentDepth + rank > ConstantUtils.MAX_ARRAY_TYPE_DESC_DIMENSIONS)
180 throw new IllegalArgumentException("rank: " + currentDepth + rank);
181 return ClassDesc.ofDescriptor("[".repeat(rank) + descriptorString());
182 }
183
184 /**
185 * Returns a {@linkplain ClassDesc} for a nested class of the class or
186 * interface type described by this {@linkplain ClassDesc}.
187 *
188 * @apiNote
189 *
190 * Example: If descriptor {@code d} describes the class {@code java.util.Map}, a
191 * descriptor for the class {@code java.util.Map.Entry} could be obtained
192 * by {@code d.nested("Entry")}.
193 *
194 * @param nestedName the unqualified name of the nested class
195 * @return a {@linkplain ClassDesc} describing the nested class
196 * @throws NullPointerException if any argument is {@code null}
197 * @throws IllegalStateException if this {@linkplain ClassDesc} does not
198 * describe a class or interface type
199 * @throws IllegalArgumentException if the nested class name is invalid
200 */
201 default ClassDesc nested(String nestedName) {
202 validateMemberName(nestedName, false);
203 if (!isClassOrInterface())
204 throw new IllegalStateException("Outer class is not a class or interface type");
205 return ClassDesc.ofDescriptor(dropLastChar(descriptorString()) + "$" + nestedName + ";");
206 }
207
208 /**
209 * Returns a {@linkplain ClassDesc} for a nested class of the class or
210 * interface type described by this {@linkplain ClassDesc}.
211 *
212 * @param firstNestedName the unqualified name of the first level of nested class
213 * @param moreNestedNames the unqualified name(s) of the remaining levels of
214 * nested class
215 * @return a {@linkplain ClassDesc} describing the nested class
216 * @throws NullPointerException if any argument is {@code null}
217 * @throws IllegalStateException if this {@linkplain ClassDesc} does not
218 * describe a class or interface type
219 * @throws IllegalArgumentException if the nested class name is invalid
220 */
221 default ClassDesc nested(String firstNestedName, String... moreNestedNames) {
222 if (!isClassOrInterface())
223 throw new IllegalStateException("Outer class is not a class or interface type");
224 return moreNestedNames.length == 0
225 ? nested(firstNestedName)
226 : nested(firstNestedName + Stream.of(moreNestedNames).collect(joining("$", "$", "")));
227 }
228
229 /**
230 * Returns whether this {@linkplain ClassDesc} describes an array type.
231 *
232 * @return whether this {@linkplain ClassDesc} describes an array type
233 */
234 default boolean isArray() {
235 return descriptorString().startsWith("[");
236 }
237
238 /**
239 * Returns whether this {@linkplain ClassDesc} describes a primitive type.
240 *
241 * @return whether this {@linkplain ClassDesc} describes a primitive type
242 */
243 default boolean isPrimitive() {
244 return descriptorString().length() == 1;
245 }
246
247 /**
248 * Returns whether this {@linkplain ClassDesc} describes a class or interface type.
249 *
250 * @return whether this {@linkplain ClassDesc} describes a class or interface type
251 */
252 default boolean isClassOrInterface() {
253 return descriptorString().startsWith("L");
254 }
255
256 /**
257 * Returns the component type of this {@linkplain ClassDesc}, if it describes
258 * an array type, or {@code null} otherwise.
259 *
260 * @return a {@linkplain ClassDesc} describing the component type, or {@code null}
261 * if this descriptor does not describe an array type
262 */
263 default ClassDesc componentType() {
264 return isArray() ? ClassDesc.ofDescriptor(descriptorString().substring(1)) : null;
265 }
266
267 /**
268 * Returns the package name of this {@linkplain ClassDesc}, if it describes
269 * a class or interface type.
270 *
271 * @return the package name, or the empty string if the class is in the
272 * default package, or this {@linkplain ClassDesc} does not describe a class or interface type
273 */
274 default String packageName() {
275 if (!isClassOrInterface())
276 return "";
277 String className = internalToBinary(ConstantUtils.dropFirstAndLastChar(descriptorString()));
278 int index = className.lastIndexOf('.');
279 return (index == -1) ? "" : className.substring(0, index);
280 }
281
282 /**
283 * Returns a human-readable name for the type described by this descriptor.
284 *
285 * @implSpec
286 * <p>The default implementation returns the simple name
287 * (e.g., {@code int}) for primitive types, the unqualified class name
288 * for class or interface types, or the display name of the component type
289 * suffixed with the appropriate number of {@code []} pairs for array types.
290 *
291 * @return the human-readable name
292 */
293 default String displayName() {
294 if (isPrimitive())
295 return Wrapper.forBasicType(descriptorString().charAt(0)).primitiveSimpleName();
296 else if (isClassOrInterface()) {
297 return descriptorString().substring(Math.max(1, descriptorString().lastIndexOf('/') + 1),
298 descriptorString().length() - 1);
299 }
300 else if (isArray()) {
301 int depth = ConstantUtils.arrayDepth(descriptorString());
302 ClassDesc c = this;
303 for (int i=0; i<depth; i++)
304 c = c.componentType();
305 return c.displayName() + "[]".repeat(depth);
306 }
307 else
308 throw new IllegalStateException(descriptorString());
309 }
310
311 /**
312 * Returns a field type descriptor string for this type
313 *
314 * @return the descriptor string
315 * @jvms 4.3.2 Field Descriptors
316 */
317 String descriptorString();
318
319 /**
320 * Compare the specified object with this descriptor for equality. Returns
321 * {@code true} if and only if the specified object is also a
322 * {@linkplain ClassDesc} and both describe the same type.
323 *
324 * @param o the other object
325 * @return whether this descriptor is equal to the other object
326 */
327 boolean equals(Object o);
328 }