1 /*
2 * Copyright (c) 2000, 2016, 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
26 package java.lang;
27
28 import jdk.internal.loader.BuiltinClassLoader;
29 import jdk.internal.misc.SharedSecrets;
30 import jdk.internal.misc.VM;
31 import jdk.internal.module.ModuleHashes;
32
33 import java.lang.reflect.Layer;
34 import java.lang.reflect.Module;
35 import java.util.HashSet;
36 import java.util.Objects;
37 import java.util.Optional;
38 import java.util.Set;
39
40 /**
41 * An element in a stack trace, as returned by {@link
42 * Throwable#getStackTrace()}. Each element represents a single stack frame.
43 * All stack frames except for the one at the top of the stack represent
44 * a method invocation. The frame at the top of the stack represents the
45 * execution point at which the stack trace was generated. Typically,
46 * this is the point at which the throwable corresponding to the stack trace
47 * was created.
48 *
49 * @since 1.4
50 * @author Josh Bloch
51 */
52 public final class StackTraceElement implements java.io.Serializable {
53
54 // For Throwables and StackWalker, the VM initially sets this field to a
55 // reference to the declaring Class. The Class reference is used to
56 // construct the 'format' bitmap, and then is cleared.
57 //
58 // For STEs constructed using the public constructors, this field is not used.
59 private transient Class<?> declaringClassObject;
60
61 // Normally initialized by VM
62 private String classLoaderName;
63 private String moduleName;
64 private String moduleVersion;
65 private String declaringClass;
66 private String methodName;
67 private String fileName;
68 private int lineNumber;
69 private byte format = 0; // Default to show all
70
71 /**
72 * Creates a stack trace element representing the specified execution
73 * point. The {@link #getModuleName module name} and {@link
74 * #getModuleVersion module version} of the stack trace element will
75 * be {@code null}.
76 *
77 * @param declaringClass the fully qualified name of the class containing
78 * the execution point represented by the stack trace element
79 * @param methodName the name of the method containing the execution point
80 * represented by the stack trace element
81 * @param fileName the name of the file containing the execution point
82 * represented by the stack trace element, or {@code null} if
83 * this information is unavailable
84 * @param lineNumber the line number of the source line containing the
85 * execution point represented by this stack trace element, or
86 * a negative number if this information is unavailable. A value
87 * of -2 indicates that the method containing the execution point
88 * is a native method
89 * @throws NullPointerException if {@code declaringClass} or
90 * {@code methodName} is null
91 * @since 1.5
92 */
93 public StackTraceElement(String declaringClass, String methodName,
94 String fileName, int lineNumber) {
95 this(null, null, null, declaringClass, methodName, fileName, lineNumber);
96 }
97
98 /**
99 * Creates a stack trace element representing the specified execution
100 * point.
101 *
102 * @param classLoaderName the class loader name if the class loader of
103 * the class containing the execution point represented by
104 * the stack trace is named; otherwise {@code null}
105 * @param moduleName the module name if the class containing the
106 * execution point represented by the stack trace is in a named
107 * module; otherwise {@code null}
108 * @param moduleVersion the module version if the class containing the
109 * execution point represented by the stack trace is in a named
110 * module that has a version; otherwise {@code null}
111 * @param declaringClass the fully qualified name of the class containing
112 * the execution point represented by the stack trace element
113 * @param methodName the name of the method containing the execution point
114 * represented by the stack trace element
115 * @param fileName the name of the file containing the execution point
116 * represented by the stack trace element, or {@code null} if
117 * this information is unavailable
118 * @param lineNumber the line number of the source line containing the
119 * execution point represented by this stack trace element, or
120 * a negative number if this information is unavailable. A value
121 * of -2 indicates that the method containing the execution point
122 * is a native method
123 *
124 * @throws NullPointerException if {@code declaringClass} is {@code null}
125 * or {@code methodName} is {@code null}
126 *
127 * @since 9
128 */
129 public StackTraceElement(String classLoaderName,
130 String moduleName, String moduleVersion,
131 String declaringClass, String methodName,
132 String fileName, int lineNumber) {
133 this.classLoaderName = classLoaderName;
134 this.moduleName = moduleName;
135 this.moduleVersion = moduleVersion;
136 this.declaringClass = Objects.requireNonNull(declaringClass, "Declaring class is null");
137 this.methodName = Objects.requireNonNull(methodName, "Method name is null");
138 this.fileName = fileName;
139 this.lineNumber = lineNumber;
140 }
141
142 /*
143 * Private constructor for the factory methods to create StackTraceElement
144 * for Throwable and StackFrameInfo
145 */
146 private StackTraceElement() {}
147
148 /**
149 * Returns the name of the source file containing the execution point
150 * represented by this stack trace element. Generally, this corresponds
151 * to the {@code SourceFile} attribute of the relevant {@code class}
152 * file (as per <i>The Java Virtual Machine Specification</i>, Section
153 * 4.7.7). In some systems, the name may refer to some source code unit
154 * other than a file, such as an entry in source repository.
155 *
156 * @return the name of the file containing the execution point
157 * represented by this stack trace element, or {@code null} if
158 * this information is unavailable.
159 */
160 public String getFileName() {
161 return fileName;
162 }
163
164 /**
165 * Returns the line number of the source line containing the execution
166 * point represented by this stack trace element. Generally, this is
167 * derived from the {@code LineNumberTable} attribute of the relevant
168 * {@code class} file (as per <i>The Java Virtual Machine
169 * Specification</i>, Section 4.7.8).
170 *
171 * @return the line number of the source line containing the execution
172 * point represented by this stack trace element, or a negative
173 * number if this information is unavailable.
174 */
175 public int getLineNumber() {
176 return lineNumber;
177 }
178
179 /**
180 * Returns the module name of the module containing the execution point
181 * represented by this stack trace element.
182 *
183 * @return the module name of the {@code Module} containing the execution
184 * point represented by this stack trace element; {@code null}
185 * if the module name is not available.
186 * @since 9
187 * @see java.lang.reflect.Module#getName()
188 */
189 public String getModuleName() {
190 return moduleName;
191 }
192
193 /**
194 * Returns the module version of the module containing the execution point
195 * represented by this stack trace element.
196 *
197 * @return the module version of the {@code Module} containing the execution
198 * point represented by this stack trace element; {@code null}
199 * if the module version is not available.
200 * @since 9
201 * @see java.lang.module.ModuleDescriptor.Version
202 */
203 public String getModuleVersion() {
204 return moduleVersion;
205 }
206
207 /**
208 * Returns the name of the class loader of the class containing the
209 * execution point represented by this stack trace element.
210 *
211 * @return the name of the class loader of the class containing the execution
212 * point represented by this stack trace element; {@code null}
213 * if the class loader is not named.
214 *
215 * @since 9
216 * @see java.lang.ClassLoader#getName()
217 */
218 public String getClassLoaderName() {
219 return classLoaderName;
220 }
221
222 /**
223 * Returns the fully qualified name of the class containing the
224 * execution point represented by this stack trace element.
225 *
226 * @return the fully qualified name of the {@code Class} containing
227 * the execution point represented by this stack trace element.
228 */
229 public String getClassName() {
230 return declaringClass;
231 }
232
233 /**
234 * Returns the name of the method containing the execution point
235 * represented by this stack trace element. If the execution point is
236 * contained in an instance or class initializer, this method will return
237 * the appropriate <i>special method name</i>, {@code <init>} or
238 * {@code <clinit>}, as per Section 3.9 of <i>The Java Virtual
239 * Machine Specification</i>.
240 *
241 * @return the name of the method containing the execution point
242 * represented by this stack trace element.
243 */
244 public String getMethodName() {
245 return methodName;
246 }
247
248 /**
249 * Returns true if the method containing the execution point
250 * represented by this stack trace element is a native method.
251 *
252 * @return {@code true} if the method containing the execution point
253 * represented by this stack trace element is a native method.
254 */
255 public boolean isNativeMethod() {
256 return lineNumber == -2;
257 }
258
259 /**
260 * Returns a string representation of this stack trace element.
261 *
262 * @apiNote The format of this string depends on the implementation, but the
263 * following examples may be regarded as typical:
264 * <ul>
265 * <li>
266 * "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Main.java:101)}"
267 * - See the description below.
268 * </li>
269 * <li>
270 * "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Main.java)}"
271 * - The line number is unavailable.
272 * </li>
273 * <li>
274 * "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Unknown Source)}"
275 * - Neither the file name nor the line number is available.
276 * </li>
277 * <li>
278 * "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Native Method)}"
279 * - The method containing the execution point is a native method.
280 * </li>
281 * <li>
282 * "{@code com.foo.loader//com.foo.bar.App.run(App.java:12)}"
283 * - The class of the execution point is defined in the unnamed module of
284 * the class loader named {@code com.foo.loader}.
285 * </li>
286 * <li>
287 * "{@code acme@2.1/org.acme.Lib.test(Lib.java:80)}"
288 * - The class of the execution point is defined in {@code acme} module
289 * loaded by by a built-in class loader such as the application class loader.
290 * </li>
291 * <li>
292 * "{@code MyClass.mash(MyClass.java:9)}"
293 * - {@code MyClass} class is on the application class path.
294 * </li>
295 * </ul>
296 *
297 * <p> The first example shows a stack trace element consisting of
298 * three elements, each separated by {@code "/"} followed with
299 * the source file name and the line number of the source line
300 * containing the execution point.
301 *
302 * The first element "{@code com.foo.loader}" is
303 * the name of the class loader. The second element "{@code foo@9.0}"
304 * is the module name and version. The third element is the method
305 * containing the execution point; "{@code com.foo.Main"}" is the
306 * fully-qualified class name and "{@code run}" is the name of the method.
307 * "{@code Main.java}" is the source file name and "{@code 101}" is
308 * the line number.
309 *
310 * <p> If a class is defined in an <em>unnamed module</em>
311 * then the second element is omitted as shown in
312 * "{@code com.foo.loader//com.foo.bar.App.run(App.java:12)}".
313 *
314 * <p> If the class loader is a <a href="ClassLoader.html#builtinLoaders">
315 * built-in class loader</a> or is not named then the first element
316 * and its following {@code "/"} are omitted as shown in
317 * "{@code acme@2.1/org.acme.Lib.test(Lib.java:80)}".
318 * If the first element is omitted and the module is an unnamed module,
319 * the second element and its following {@code "/"} are also omitted
320 * as shown in "{@code MyClass.mash(MyClass.java:9)}".
321 *
322 * <p> The {@code toString} method may return two different values on two
323 * {@code StackTraceElement} instances that are
324 * {@linkplain #equals(Object) equal}, for example one created via the
325 * constructor, and one obtained from {@link java.lang.Throwable} or
326 * {@link java.lang.StackWalker.StackFrame}, where an implementation may
327 * choose to omit some element in the returned string.
328 *
329 * @see Throwable#printStackTrace()
330 */
331 public String toString() {
332 String s = "";
333 if (!dropClassLoaderName() && classLoaderName != null &&
334 !classLoaderName.isEmpty()) {
335 s += classLoaderName + "/";
336 }
337 if (moduleName != null && !moduleName.isEmpty()) {
338 s += moduleName;
339
340 if (!dropModuleVersion() && moduleVersion != null &&
341 !moduleVersion.isEmpty()) {
342 s += "@" + moduleVersion;
343 }
344 }
345 s = s.isEmpty() ? declaringClass : s + "/" + declaringClass;
346
347 return s + "." + methodName + "(" +
348 (isNativeMethod() ? "Native Method)" :
349 (fileName != null && lineNumber >= 0 ?
350 fileName + ":" + lineNumber + ")" :
351 (fileName != null ? ""+fileName+")" : "Unknown Source)")));
352 }
353
354 /**
355 * Returns true if the specified object is another
356 * {@code StackTraceElement} instance representing the same execution
357 * point as this instance. Two stack trace elements {@code a} and
358 * {@code b} are equal if and only if:
359 * <pre>{@code
360 * equals(a.getClassLoaderName(), b.getClassLoaderName()) &&
361 * equals(a.getModuleName(), b.getModuleName()) &&
362 * equals(a.getModuleVersion(), b.getModuleVersion()) &&
363 * equals(a.getClassName(), b.getClassName()) &&
364 * equals(a.getMethodName(), b.getMethodName())
365 * equals(a.getFileName(), b.getFileName()) &&
366 * a.getLineNumber() == b.getLineNumber()
367 *
368 * }</pre>
369 * where {@code equals} has the semantics of {@link
370 * java.util.Objects#equals(Object, Object) Objects.equals}.
371 *
372 * @param obj the object to be compared with this stack trace element.
373 * @return true if the specified object is another
374 * {@code StackTraceElement} instance representing the same
375 * execution point as this instance.
376 */
377 public boolean equals(Object obj) {
378 if (obj==this)
379 return true;
380 if (!(obj instanceof StackTraceElement))
381 return false;
382 StackTraceElement e = (StackTraceElement)obj;
383 return Objects.equals(classLoaderName, e.classLoaderName) &&
384 Objects.equals(moduleName, e.moduleName) &&
385 Objects.equals(moduleVersion, e.moduleVersion) &&
386 e.declaringClass.equals(declaringClass) &&
387 e.lineNumber == lineNumber &&
388 Objects.equals(methodName, e.methodName) &&
389 Objects.equals(fileName, e.fileName);
390 }
391
392 /**
393 * Returns a hash code value for this stack trace element.
394 */
395 public int hashCode() {
396 int result = 31*declaringClass.hashCode() + methodName.hashCode();
397 result = 31*result + Objects.hashCode(classLoaderName);
398 result = 31*result + Objects.hashCode(moduleName);
399 result = 31*result + Objects.hashCode(moduleVersion);
400 result = 31*result + Objects.hashCode(fileName);
401 result = 31*result + lineNumber;
402 return result;
403 }
404
405
406 /**
407 * Called from of() methods to set the 'format' bitmap using the Class
408 * reference stored in declaringClassObject, and then clear the reference.
409 *
410 * <p>
411 * If the module is a non-upgradeable JDK module, then set
412 * JDK_NON_UPGRADEABLE_MODULE to omit its version string.
413 * <p>
414 * If the loader is one of the built-in loaders (`boot`, `platform`, or `app`)
415 * then set BUILTIN_CLASS_LOADER to omit the first element (`<loader>/`).
416 */
417 private synchronized void computeFormat() {
418 try {
419 Class<?> cls = (Class<?>) declaringClassObject;
420 ClassLoader loader = cls.getClassLoader0();
421 Module m = cls.getModule();
422 byte bits = 0;
423
424 // First element - class loader name
425 // Call package-private ClassLoader::name method
426
427 if (loader instanceof BuiltinClassLoader) {
428 bits |= BUILTIN_CLASS_LOADER;
429 }
430
431 // Second element - module name and version
432
433 // Omit if is a JDK non-upgradeable module (recorded in the hashes
434 // in java.base)
435 if (isHashedInJavaBase(m)) {
436 bits |= JDK_NON_UPGRADEABLE_MODULE;
437 }
438 format = bits;
439 } finally {
440 // Class reference no longer needed, clear it
441 declaringClassObject = null;
442 }
443 }
444
445 private static final byte BUILTIN_CLASS_LOADER = 0x1;
446 private static final byte JDK_NON_UPGRADEABLE_MODULE = 0x2;
447
448 private boolean dropClassLoaderName() {
449 return (format & BUILTIN_CLASS_LOADER) == BUILTIN_CLASS_LOADER;
450 }
451
452 private boolean dropModuleVersion() {
453 return (format & JDK_NON_UPGRADEABLE_MODULE) == JDK_NON_UPGRADEABLE_MODULE;
454 }
455
456 /**
457 * Returns true if the module is hashed with java.base.
458 * <p>
459 * This method returns false when running on the exploded image
460 * since JDK modules are not hashed. They have no Version attribute
461 * and so "@<version>" part will be omitted anyway.
462 */
463 private static boolean isHashedInJavaBase(Module m) {
464 // return true if module system is not initialized as the code
465 // must be in java.base
466 if (!VM.isModuleSystemInited())
467 return true;
468
469 return Layer.boot() == m.getLayer() && HashedModules.contains(m);
470 }
471
472 /*
473 * Finds JDK non-upgradeable modules, i.e. the modules that are
474 * included in the hashes in java.base.
475 */
476 private static class HashedModules {
477 static Set<String> HASHED_MODULES = hashedModules();
478
479 static Set<String> hashedModules() {
480 Module javaBase = Layer.boot().findModule("java.base").get();
481 Optional<ModuleHashes> ohashes =
482 SharedSecrets.getJavaLangModuleAccess()
483 .hashes(javaBase.getDescriptor());
484
485 if (ohashes.isPresent()) {
486 Set<String> names = new HashSet<>(ohashes.get().names());
487 names.add("java.base");
488 return names;
489 }
490
491 return Set.of();
492 }
493
494 static boolean contains(Module m) {
495 return HASHED_MODULES.contains(m.getName());
496 }
497 }
498
499
500 /*
501 * Returns an array of StackTraceElements of the given depth
502 * filled from the backtrace of a given Throwable.
503 */
504 static StackTraceElement[] of(Throwable x, int depth) {
505 StackTraceElement[] stackTrace = new StackTraceElement[depth];
506 for (int i = 0; i < depth; i++) {
507 stackTrace[i] = new StackTraceElement();
508 }
509
510 // VM to fill in StackTraceElement
511 initStackTraceElements(stackTrace, x);
512
513 // ensure the proper StackTraceElement initialization
514 for (StackTraceElement ste : stackTrace) {
515 ste.computeFormat();
516 }
517 return stackTrace;
518 }
519
520 /*
521 * Returns a StackTraceElement from a given StackFrameInfo.
522 */
523 static StackTraceElement of(StackFrameInfo sfi) {
524 StackTraceElement ste = new StackTraceElement();
525 initStackTraceElement(ste, sfi);
526
527 ste.computeFormat();
528 return ste;
529 }
530
531 /*
532 * Sets the given stack trace elements with the backtrace
533 * of the given Throwable.
534 */
535 private static native void initStackTraceElements(StackTraceElement[] elements,
536 Throwable x);
537 /*
538 * Sets the given stack trace element with the given StackFrameInfo
539 */
540 private static native void initStackTraceElement(StackTraceElement element,
541 StackFrameInfo sfi);
542
543 private static final long serialVersionUID = 6992337162326171013L;
544 }