1 /*
2 * Copyright (c) 2018, 2021, 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 * @see ConstantDescs
53 *
54 * @since 12
55 */
56 public sealed interface ClassDesc
57 extends ConstantDesc,
58 TypeDescriptor.OfField<ClassDesc>
59 permits PrimitiveClassDescImpl,
60 ReferenceClassDescImpl {
61
62 /**
63 * Returns a {@linkplain ClassDesc} for a class or interface type,
64 * given the name of the class or interface, such as {@code "java.lang.String"}.
65 * (To create a descriptor for an array type, either use {@link #ofDescriptor(String)}
66 * or {@link #arrayType()}; to create a descriptor for a primitive type, use
67 * {@link #ofDescriptor(String)} or use the predefined constants in
68 * {@link ConstantDescs}).
69 *
70 * @param name the fully qualified (dot-separated) binary class name
71 * @return a {@linkplain ClassDesc} describing the desired class
72 * @throws NullPointerException if the argument is {@code null}
73 * @throws IllegalArgumentException if the name string is not in the
74 * correct format
75 */
76 static ClassDesc of(String name) {
77 ConstantUtils.validateBinaryClassName(requireNonNull(name));
78 return ClassDesc.ofDescriptor("L" + binaryToInternal(name) + ";");
79 }
80
81 /**
82 * Returns a {@linkplain ClassDesc} for a class or interface type,
83 * given a package name and the unqualified (simple) name for the
84 * class or interface.
85 *
86 * @param packageName the package name (dot-separated); if the package
87 * name is the empty string, the class is considered to
88 * be in the unnamed package
89 * @param className the unqualified (simple) class name
90 * @return a {@linkplain ClassDesc} describing the desired class
91 * @throws NullPointerException if any argument is {@code null}
92 * @throws IllegalArgumentException if the package name or class name are
93 * not in the correct format
94 */
95 static ClassDesc of(String packageName, String className) {
96 ConstantUtils.validateBinaryClassName(requireNonNull(packageName));
97 if (packageName.isEmpty()) {
98 return of(className);
99 }
100 validateMemberName(requireNonNull(className), false);
101 return ofDescriptor("L" + binaryToInternal(packageName) +
102 "/" + className + ";");
103 }
104
105 /**
106 * Returns a {@linkplain ClassDesc} given a descriptor string for a class,
107 * interface, array, or primitive type.
108 *
109 * @apiNote
110 *
111 * A field type descriptor string for a non-array type is either
112 * a one-letter code corresponding to a primitive type
113 * ({@code "J", "I", "C", "S", "B", "D", "F", "Z", "V"}), or the letter {@code "L"}, followed
114 * by the fully qualified binary name of a class, followed by {@code ";"}.
115 * A field type descriptor for an array type is the character {@code "["}
116 * followed by the field descriptor for the component type. Examples of
117 * valid type descriptor strings include {@code "Ljava/lang/String;"}, {@code "I"},
118 * {@code "[I"}, {@code "V"}, {@code "[Ljava/lang/String;"}, etc.
119 * See JVMS 4.3.2 ("Field Descriptors") for more detail.
120 *
121 * @param descriptor a field descriptor string
122 * @return a {@linkplain ClassDesc} describing the desired class
123 * @throws NullPointerException if the argument is {@code null}
124 * @throws IllegalArgumentException if the name string is not in the
125 * correct format
126 * @jvms 4.3.2 Field Descriptors
127 * @jvms 4.4.1 The CONSTANT_Class_info Structure
128 */
129 static ClassDesc ofDescriptor(String descriptor) {
130 requireNonNull(descriptor);
131 if (descriptor.isEmpty()) {
132 throw new IllegalArgumentException(
133 "not a valid reference type descriptor: " + descriptor);
134 }
135 int depth = ConstantUtils.arrayDepth(descriptor);
136 if (depth > ConstantUtils.MAX_ARRAY_TYPE_DESC_DIMENSIONS) {
137 throw new IllegalArgumentException(
138 "Cannot create an array type descriptor with more than " +
139 ConstantUtils.MAX_ARRAY_TYPE_DESC_DIMENSIONS + " dimensions");
140 }
141 return (descriptor.length() == 1)
142 ? new PrimitiveClassDescImpl(descriptor)
143 : new ReferenceClassDescImpl(descriptor);
144 }
145
146 /**
147 * Returns a {@linkplain ClassDesc} for an array type whose component type
148 * is described by this {@linkplain ClassDesc}.
149 *
150 * @return a {@linkplain ClassDesc} describing the array type
151 * @throws IllegalStateException if the resulting {@linkplain ClassDesc} would have an array rank of greater than 255
152 * @jvms 4.4.1 The CONSTANT_Class_info Structure
153 */
154 default ClassDesc arrayType() {
155 int depth = ConstantUtils.arrayDepth(descriptorString());
156 if (depth >= ConstantUtils.MAX_ARRAY_TYPE_DESC_DIMENSIONS) {
157 throw new IllegalStateException(
158 "Cannot create an array type descriptor with more than " +
159 ConstantUtils.MAX_ARRAY_TYPE_DESC_DIMENSIONS + " dimensions");
160 }
161 return arrayType(1);
162 }
163
164 /**
165 * Returns a {@linkplain ClassDesc} for an array type of the specified rank,
166 * whose component type is described by this {@linkplain ClassDesc}.
167 *
168 * @param rank the rank of the array
169 * @return a {@linkplain ClassDesc} describing the array type
170 * @throws IllegalArgumentException if the rank is less than or equal to zero or if the rank of the resulting array type is
171 * greater than 255
172 * @jvms 4.4.1 The CONSTANT_Class_info Structure
173 */
174 default ClassDesc arrayType(int rank) {
175 int currentDepth = ConstantUtils.arrayDepth(descriptorString());
176 if (rank <= 0 || currentDepth + rank > ConstantUtils.MAX_ARRAY_TYPE_DESC_DIMENSIONS)
177 throw new IllegalArgumentException("rank: " + currentDepth + rank);
178 return ClassDesc.ofDescriptor("[".repeat(rank) + descriptorString());
179 }
180
181 /**
182 * Returns a {@linkplain ClassDesc} for a nested class of the class or
183 * interface type described by this {@linkplain ClassDesc}.
184 *
185 * @apiNote
186 *
187 * Example: If descriptor {@code d} describes the class {@code java.util.Map}, a
188 * descriptor for the class {@code java.util.Map.Entry} could be obtained
189 * by {@code d.nested("Entry")}.
190 *
191 * @param nestedName the unqualified name of the nested class
192 * @return a {@linkplain ClassDesc} describing the nested class
193 * @throws NullPointerException if the argument is {@code null}
194 * @throws IllegalStateException if this {@linkplain ClassDesc} does not
195 * describe a class or interface type
196 * @throws IllegalArgumentException if the nested class name is invalid
197 */
198 default ClassDesc nested(String nestedName) {
199 validateMemberName(nestedName, false);
200 if (!isClassOrInterface())
201 throw new IllegalStateException("Outer class is not a class or interface type");
202 return ClassDesc.ofDescriptor(dropLastChar(descriptorString()) + "$" + nestedName + ";");
203 }
204
205 /**
206 * Returns a {@linkplain ClassDesc} for a nested class of the class or
207 * interface type described by this {@linkplain ClassDesc}.
208 *
209 * @param firstNestedName the unqualified name of the first level of nested class
210 * @param moreNestedNames the unqualified name(s) of the remaining levels of
211 * nested class
212 * @return a {@linkplain ClassDesc} describing the nested class
213 * @throws NullPointerException if any argument or its contents is {@code null}
214 * @throws IllegalStateException if this {@linkplain ClassDesc} does not
215 * describe a class or interface type
216 * @throws IllegalArgumentException if the nested class name is invalid
217 */
218 default ClassDesc nested(String firstNestedName, String... moreNestedNames) {
219 if (!isClassOrInterface())
220 throw new IllegalStateException("Outer class is not a class or interface type");
221 validateMemberName(firstNestedName, false);
222 requireNonNull(moreNestedNames);
223 for (String addNestedNames : moreNestedNames) {
224 validateMemberName(addNestedNames, false);
225 }
226 return moreNestedNames.length == 0
227 ? nested(firstNestedName)
228 : nested(firstNestedName + Stream.of(moreNestedNames).collect(joining("$", "$", "")));
229 }
230
231 /**
232 * Returns whether this {@linkplain ClassDesc} describes an array type.
233 *
234 * @return whether this {@linkplain ClassDesc} describes an array type
235 */
236 default boolean isArray() {
237 return descriptorString().startsWith("[");
238 }
239
240 /**
241 * Returns whether this {@linkplain ClassDesc} describes a primitive type.
242 *
243 * @return whether this {@linkplain ClassDesc} describes a primitive type
244 */
245 default boolean isPrimitive() {
246 return descriptorString().length() == 1;
247 }
248
249 /**
250 * Returns whether this {@linkplain ClassDesc} describes a class or interface type.
251 *
252 * @return whether this {@linkplain ClassDesc} describes a class or interface type
253 */
254 default boolean isClassOrInterface() {
255 return descriptorString().startsWith("L");
256 }
257
258 /**
259 * Returns the component type of this {@linkplain ClassDesc}, if it describes
260 * an array type, or {@code null} otherwise.
261 *
262 * @return a {@linkplain ClassDesc} describing the component type, or {@code null}
263 * if this descriptor does not describe an array type
264 */
265 default ClassDesc componentType() {
266 return isArray() ? ClassDesc.ofDescriptor(descriptorString().substring(1)) : null;
267 }
268
269 /**
270 * Returns the package name of this {@linkplain ClassDesc}, if it describes
271 * a class or interface type.
272 *
273 * @return the package name, or the empty string if the class is in the
274 * default package, or this {@linkplain ClassDesc} does not describe a class or interface type
275 */
276 default String packageName() {
277 if (!isClassOrInterface())
278 return "";
279 String className = internalToBinary(ConstantUtils.dropFirstAndLastChar(descriptorString()));
280 int index = className.lastIndexOf('.');
281 return (index == -1) ? "" : className.substring(0, index);
282 }
283
284 /**
285 * Returns a human-readable name for the type described by this descriptor.
286 *
287 * @implSpec
288 * <p>The default implementation returns the simple name
289 * (e.g., {@code int}) for primitive types, the unqualified class name
290 * for class or interface types, or the display name of the component type
291 * suffixed with the appropriate number of {@code []} pairs for array types.
292 *
293 * @return the human-readable name
294 */
295 default String displayName() {
296 if (isPrimitive())
297 return Wrapper.forBasicType(descriptorString().charAt(0)).primitiveSimpleName();
298 else if (isClassOrInterface()) {
299 return descriptorString().substring(Math.max(1, descriptorString().lastIndexOf('/') + 1),
300 descriptorString().length() - 1);
301 }
302 else if (isArray()) {
303 int depth = ConstantUtils.arrayDepth(descriptorString());
304 ClassDesc c = this;
305 for (int i=0; i<depth; i++)
306 c = c.componentType();
307 return c.displayName() + "[]".repeat(depth);
308 }
309 else
310 throw new IllegalStateException(descriptorString());
311 }
312
313 /**
314 * Returns a field type descriptor string for this type
315 *
316 * @return the descriptor string
317 * @jvms 4.3.2 Field Descriptors
318 */
319 String descriptorString();
320
321 /**
322 * Compare the specified object with this descriptor for equality. Returns
323 * {@code true} if and only if the specified object is also a
324 * {@linkplain ClassDesc} and both describe the same type.
325 *
326 * @param o the other object
327 * @return whether this descriptor is equal to the other object
328 */
329 boolean equals(Object o);
330 }