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.VM;
30 import jdk.internal.module.ModuleHashes;
31 import jdk.internal.module.ModuleReferenceImpl;
32
33 import java.lang.module.ModuleDescriptor.Version;
34 import java.lang.module.ModuleReference;
35 import java.lang.module.ResolvedModule;
36 import java.util.HashSet;
37 import java.util.Objects;
38 import java.util.Optional;
39 import java.util.Set;
40
41 /**
42 * An element in a stack trace, as returned by {@link
43 * Throwable#getStackTrace()}. Each element represents a single stack frame.
44 * All stack frames except for the one at the top of the stack represent
45 * a method invocation. The frame at the top of the stack represents the
46 * execution point at which the stack trace was generated. Typically,
47 * this is the point at which the throwable corresponding to the stack trace
48 * was created.
49 *
50 * @since 1.4
51 * @author Josh Bloch
52 */
53 public final class StackTraceElement implements java.io.Serializable {
54
55 // For Throwables and StackWalker, the VM initially sets this field to a
56 // reference to the declaring Class. The Class reference is used to
57 // construct the 'format' bitmap, and then is cleared.
58 //
59 // For STEs constructed using the public constructors, this field is not used.
60 private transient Class<?> declaringClassObject;
61
62 // Normally initialized by VM
63 private String classLoaderName;
64 private String moduleName;
65 private String moduleVersion;
66 private String declaringClass;
67 private String methodName;
68 private String fileName;
69 private int lineNumber;
70 private byte format = 0; // Default to show all
71
72 /**
73 * Creates a stack trace element representing the specified execution
74 * point. The {@link #getModuleName module name} and {@link
75 * #getModuleVersion module version} of the stack trace element will
76 * be {@code null}.
77 *
78 * @param declaringClass the fully qualified name of the class containing
79 * the execution point represented by the stack trace element
80 * @param methodName the name of the method containing the execution point
81 * represented by the stack trace element
82 * @param fileName the name of the file containing the execution point
83 * represented by the stack trace element, or {@code null} if
84 * this information is unavailable
85 * @param lineNumber the line number of the source line containing the
86 * execution point represented by this stack trace element, or
87 * a negative number if this information is unavailable. A value
88 * of -2 indicates that the method containing the execution point
89 * is a native method
90 * @throws NullPointerException if {@code declaringClass} or
91 * {@code methodName} is null
92 * @since 1.5
93 * @revised 9
94 * @spec JPMS
95 */
96 public StackTraceElement(String declaringClass, String methodName,
97 String fileName, int lineNumber) {
98 this(null, null, null, declaringClass, methodName, fileName, lineNumber);
99 }
100
101 /**
102 * Creates a stack trace element representing the specified execution
103 * point.
104 *
105 * @param classLoaderName the class loader name if the class loader of
106 * the class containing the execution point represented by
107 * the stack trace is named; otherwise {@code null}
108 * @param moduleName the module name if the class containing the
109 * execution point represented by the stack trace is in a named
110 * module; otherwise {@code null}
111 * @param moduleVersion the module version if the class containing the
112 * execution point represented by the stack trace is in a named
113 * module that has a version; otherwise {@code null}
114 * @param declaringClass the fully qualified name of the class containing
115 * the execution point represented by the stack trace element
116 * @param methodName the name of the method containing the execution point
117 * represented by the stack trace element
118 * @param fileName the name of the file containing the execution point
119 * represented by the stack trace element, or {@code null} if
120 * this information is unavailable
121 * @param lineNumber the line number of the source line containing the
122 * execution point represented by this stack trace element, or
123 * a negative number if this information is unavailable. A value
124 * of -2 indicates that the method containing the execution point
125 * is a native method
126 *
127 * @throws NullPointerException if {@code declaringClass} is {@code null}
128 * or {@code methodName} is {@code null}
129 *
130 * @since 9
131 * @spec JPMS
132 */
133 public StackTraceElement(String classLoaderName,
134 String moduleName, String moduleVersion,
135 String declaringClass, String methodName,
136 String fileName, int lineNumber) {
137 this.classLoaderName = classLoaderName;
138 this.moduleName = moduleName;
139 this.moduleVersion = moduleVersion;
140 this.declaringClass = Objects.requireNonNull(declaringClass, "Declaring class is null");
141 this.methodName = Objects.requireNonNull(methodName, "Method name is null");
142 this.fileName = fileName;
143 this.lineNumber = lineNumber;
144 }
145
146 /*
147 * Private constructor for the factory methods to create StackTraceElement
148 * for Throwable and StackFrameInfo
149 */
150 private StackTraceElement() {}
151
152 /**
153 * Returns the name of the source file containing the execution point
154 * represented by this stack trace element. Generally, this corresponds
155 * to the {@code SourceFile} attribute of the relevant {@code class}
156 * file (as per <i>The Java Virtual Machine Specification</i>, Section
157 * 4.7.7). In some systems, the name may refer to some source code unit
158 * other than a file, such as an entry in source repository.
159 *
160 * @return the name of the file containing the execution point
161 * represented by this stack trace element, or {@code null} if
162 * this information is unavailable.
163 */
164 public String getFileName() {
165 return fileName;
166 }
167
168 /**
169 * Returns the line number of the source line containing the execution
170 * point represented by this stack trace element. Generally, this is
171 * derived from the {@code LineNumberTable} attribute of the relevant
172 * {@code class} file (as per <i>The Java Virtual Machine
173 * Specification</i>, Section 4.7.8).
174 *
175 * @return the line number of the source line containing the execution
176 * point represented by this stack trace element, or a negative
177 * number if this information is unavailable.
178 */
179 public int getLineNumber() {
180 return lineNumber;
181 }
182
183 /**
184 * Returns the module name of the module containing the execution point
185 * represented by this stack trace element.
186 *
187 * @return the module name of the {@code Module} containing the execution
188 * point represented by this stack trace element; {@code null}
189 * if the module name is not available.
190 * @since 9
191 * @spec JPMS
192 * @see Module#getName()
193 */
194 public String getModuleName() {
195 return moduleName;
196 }
197
198 /**
199 * Returns the module version of the module containing the execution point
200 * represented by this stack trace element.
201 *
202 * @return the module version of the {@code Module} containing the execution
203 * point represented by this stack trace element; {@code null}
204 * if the module version is not available.
205 * @since 9
206 * @spec JPMS
207 * @see java.lang.module.ModuleDescriptor.Version
208 */
209 public String getModuleVersion() {
210 return moduleVersion;
211 }
212
213 /**
214 * Returns the name of the class loader of the class containing the
215 * execution point represented by this stack trace element.
216 *
217 * @return the name of the class loader of the class containing the execution
218 * point represented by this stack trace element; {@code null}
219 * if the class loader is not named.
220 *
221 * @since 9
222 * @spec JPMS
223 * @see java.lang.ClassLoader#getName()
224 */
225 public String getClassLoaderName() {
226 return classLoaderName;
227 }
228
229 /**
230 * Returns the fully qualified name of the class containing the
231 * execution point represented by this stack trace element.
232 *
233 * @return the fully qualified name of the {@code Class} containing
234 * the execution point represented by this stack trace element.
235 */
236 public String getClassName() {
237 return declaringClass;
238 }
239
240 /**
241 * Returns the name of the method containing the execution point
242 * represented by this stack trace element. If the execution point is
243 * contained in an instance or class initializer, this method will return
244 * the appropriate <i>special method name</i>, {@code <init>} or
245 * {@code <clinit>}, as per Section 3.9 of <i>The Java Virtual
246 * Machine Specification</i>.
247 *
248 * @return the name of the method containing the execution point
249 * represented by this stack trace element.
250 */
251 public String getMethodName() {
252 return methodName;
253 }
254
255 /**
256 * Returns true if the method containing the execution point
257 * represented by this stack trace element is a native method.
258 *
259 * @return {@code true} if the method containing the execution point
260 * represented by this stack trace element is a native method.
261 */
262 public boolean isNativeMethod() {
263 return lineNumber == -2;
264 }
265
266 /**
267 * Returns a string representation of this stack trace element.
268 *
269 * @apiNote The format of this string depends on the implementation, but the
270 * following examples may be regarded as typical:
271 * <ul>
272 * <li>
273 * "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Main.java:101)}"
274 * - See the description below.
275 * </li>
276 * <li>
277 * "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Main.java)}"
278 * - The line number is unavailable.
279 * </li>
280 * <li>
281 * "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Unknown Source)}"
282 * - Neither the file name nor the line number is available.
283 * </li>
284 * <li>
285 * "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Native Method)}"
286 * - The method containing the execution point is a native method.
287 * </li>
288 * <li>
289 * "{@code com.foo.loader//com.foo.bar.App.run(App.java:12)}"
290 * - The class of the execution point is defined in the unnamed module of
291 * the class loader named {@code com.foo.loader}.
292 * </li>
293 * <li>
294 * "{@code acme@2.1/org.acme.Lib.test(Lib.java:80)}"
295 * - The class of the execution point is defined in {@code acme} module
296 * loaded by a built-in class loader such as the application class loader.
297 * </li>
298 * <li>
299 * "{@code MyClass.mash(MyClass.java:9)}"
300 * - {@code MyClass} class is on the application class path.
301 * </li>
302 * </ul>
303 *
304 * <p> The first example shows a stack trace element consisting of
305 * three elements, each separated by {@code "/"} followed with
306 * the source file name and the line number of the source line
307 * containing the execution point.
308 *
309 * The first element "{@code com.foo.loader}" is
310 * the name of the class loader. The second element "{@code foo@9.0}"
311 * is the module name and version. The third element is the method
312 * containing the execution point; "{@code com.foo.Main"}" is the
313 * fully-qualified class name and "{@code run}" is the name of the method.
314 * "{@code Main.java}" is the source file name and "{@code 101}" is
315 * the line number.
316 *
317 * <p> If a class is defined in an <em>unnamed module</em>
318 * then the second element is omitted as shown in
319 * "{@code com.foo.loader//com.foo.bar.App.run(App.java:12)}".
320 *
321 * <p> If the class loader is a <a href="ClassLoader.html#builtinLoaders">
322 * built-in class loader</a> or is not named then the first element
323 * and its following {@code "/"} are omitted as shown in
324 * "{@code acme@2.1/org.acme.Lib.test(Lib.java:80)}".
325 * If the first element is omitted and the module is an unnamed module,
326 * the second element and its following {@code "/"} are also omitted
327 * as shown in "{@code MyClass.mash(MyClass.java:9)}".
328 *
329 * <p> The {@code toString} method may return two different values on two
330 * {@code StackTraceElement} instances that are
331 * {@linkplain #equals(Object) equal}, for example one created via the
332 * constructor, and one obtained from {@link java.lang.Throwable} or
333 * {@link java.lang.StackWalker.StackFrame}, where an implementation may
334 * choose to omit some element in the returned string.
335 *
336 * @revised 9
337 * @spec JPMS
338 * @see Throwable#printStackTrace()
339 */
340 public String toString() {
341 String s = "";
342 if (!dropClassLoaderName() && classLoaderName != null &&
343 !classLoaderName.isEmpty()) {
344 s += classLoaderName + "/";
345 }
346 if (moduleName != null && !moduleName.isEmpty()) {
347 s += moduleName;
348
349 if (!dropModuleVersion() && moduleVersion != null &&
350 !moduleVersion.isEmpty()) {
351 s += "@" + moduleVersion;
352 }
353 }
354 s = s.isEmpty() ? declaringClass : s + "/" + declaringClass;
355
356 return s + "." + methodName + "(" +
357 (isNativeMethod() ? "Native Method)" :
358 (fileName != null && lineNumber >= 0 ?
359 fileName + ":" + lineNumber + ")" :
360 (fileName != null ? ""+fileName+")" : "Unknown Source)")));
361 }
362
363 /**
364 * Returns true if the specified object is another
365 * {@code StackTraceElement} instance representing the same execution
366 * point as this instance. Two stack trace elements {@code a} and
367 * {@code b} are equal if and only if:
368 * <pre>{@code
369 * equals(a.getClassLoaderName(), b.getClassLoaderName()) &&
370 * equals(a.getModuleName(), b.getModuleName()) &&
371 * equals(a.getModuleVersion(), b.getModuleVersion()) &&
372 * equals(a.getClassName(), b.getClassName()) &&
373 * equals(a.getMethodName(), b.getMethodName())
374 * equals(a.getFileName(), b.getFileName()) &&
375 * a.getLineNumber() == b.getLineNumber()
376 *
377 * }</pre>
378 * where {@code equals} has the semantics of {@link
379 * java.util.Objects#equals(Object, Object) Objects.equals}.
380 *
381 * @param obj the object to be compared with this stack trace element.
382 * @return true if the specified object is another
383 * {@code StackTraceElement} instance representing the same
384 * execution point as this instance.
385 *
386 * @revised 9
387 * @spec JPMS
388 */
389 public boolean equals(Object obj) {
390 if (obj==this)
391 return true;
392 if (!(obj instanceof StackTraceElement))
393 return false;
394 StackTraceElement e = (StackTraceElement)obj;
395 return Objects.equals(classLoaderName, e.classLoaderName) &&
396 Objects.equals(moduleName, e.moduleName) &&
397 Objects.equals(moduleVersion, e.moduleVersion) &&
398 e.declaringClass.equals(declaringClass) &&
399 e.lineNumber == lineNumber &&
400 Objects.equals(methodName, e.methodName) &&
401 Objects.equals(fileName, e.fileName);
402 }
403
404 /**
405 * Returns a hash code value for this stack trace element.
406 */
407 public int hashCode() {
408 int result = 31*declaringClass.hashCode() + methodName.hashCode();
409 result = 31*result + Objects.hashCode(classLoaderName);
410 result = 31*result + Objects.hashCode(moduleName);
411 result = 31*result + Objects.hashCode(moduleVersion);
412 result = 31*result + Objects.hashCode(fileName);
413 result = 31*result + lineNumber;
414 return result;
415 }
416
417
418 /**
419 * Called from of() methods to set the 'format' bitmap using the Class
420 * reference stored in declaringClassObject, and then clear the reference.
421 *
422 * <p>
423 * If the module is a non-upgradeable JDK module, then set
424 * JDK_NON_UPGRADEABLE_MODULE to omit its version string.
425 * <p>
426 * If the loader is one of the built-in loaders (`boot`, `platform`, or `app`)
427 * then set BUILTIN_CLASS_LOADER to omit the first element (`<loader>/`).
428 */
429 private synchronized void computeFormat() {
430 try {
431 Class<?> cls = (Class<?>) declaringClassObject;
432 ClassLoader loader = cls.getClassLoader0();
433 Module m = cls.getModule();
434 byte bits = 0;
435
436 // First element - class loader name
437 // Call package-private ClassLoader::name method
438
439 if (loader instanceof BuiltinClassLoader) {
440 bits |= BUILTIN_CLASS_LOADER;
441 }
442
443 // Second element - module name and version
444
445 // Omit if is a JDK non-upgradeable module (recorded in the hashes
446 // in java.base)
447 if (isHashedInJavaBase(m)) {
448 bits |= JDK_NON_UPGRADEABLE_MODULE;
449 }
450 format = bits;
451 } finally {
452 // Class reference no longer needed, clear it
453 declaringClassObject = null;
454 }
455 }
456
457 private static final byte BUILTIN_CLASS_LOADER = 0x1;
458 private static final byte JDK_NON_UPGRADEABLE_MODULE = 0x2;
459
460 private boolean dropClassLoaderName() {
461 return (format & BUILTIN_CLASS_LOADER) == BUILTIN_CLASS_LOADER;
462 }
463
464 private boolean dropModuleVersion() {
465 return (format & JDK_NON_UPGRADEABLE_MODULE) == JDK_NON_UPGRADEABLE_MODULE;
466 }
467
468 /**
469 * Returns true if the module is hashed with java.base.
470 * <p>
471 * This method returns false when running on the exploded image
472 * since JDK modules are not hashed. They have no Version attribute
473 * and so "@<version>" part will be omitted anyway.
474 */
475 private static boolean isHashedInJavaBase(Module m) {
476 // return true if module system is not initialized as the code
477 // must be in java.base
478 if (!VM.isModuleSystemInited())
479 return true;
480
481 return ModuleLayer.boot() == m.getLayer() && HashedModules.contains(m);
482 }
483
484 /*
485 * Finds JDK non-upgradeable modules, i.e. the modules that are
486 * included in the hashes in java.base.
487 */
488 private static class HashedModules {
489 static Set<String> HASHED_MODULES = hashedModules();
490
491 static Set<String> hashedModules() {
492
493 Optional<ResolvedModule> resolvedModule = ModuleLayer.boot()
494 .configuration()
495 .findModule("java.base");
496 assert resolvedModule.isPresent();
497 ModuleReference mref = resolvedModule.get().reference();
498 assert mref instanceof ModuleReferenceImpl;
499 ModuleHashes hashes = ((ModuleReferenceImpl)mref).recordedHashes();
500 if (hashes != null) {
501 Set<String> names = new HashSet<>(hashes.names());
502 names.add("java.base");
503 return names;
504 }
505
506 return Set.of();
507 }
508
509 static boolean contains(Module m) {
510 return HASHED_MODULES.contains(m.getName());
511 }
512 }
513
514
515 /*
516 * Returns an array of StackTraceElements of the given depth
517 * filled from the backtrace of a given Throwable.
518 */
519 static StackTraceElement[] of(Throwable x, int depth) {
520 StackTraceElement[] stackTrace = new StackTraceElement[depth];
521 for (int i = 0; i < depth; i++) {
522 stackTrace[i] = new StackTraceElement();
523 }
524
525 // VM to fill in StackTraceElement
526 initStackTraceElements(stackTrace, x);
527
528 // ensure the proper StackTraceElement initialization
529 for (StackTraceElement ste : stackTrace) {
530 ste.computeFormat();
531 }
532 return stackTrace;
533 }
534
535 /*
536 * Returns a StackTraceElement from a given StackFrameInfo.
537 */
538 static StackTraceElement of(StackFrameInfo sfi) {
539 StackTraceElement ste = new StackTraceElement();
540 initStackTraceElement(ste, sfi);
541
542 ste.computeFormat();
543 return ste;
544 }
545
546 /*
547 * Sets the given stack trace elements with the backtrace
548 * of the given Throwable.
549 */
550 private static native void initStackTraceElements(StackTraceElement[] elements,
551 Throwable x);
552 /*
553 * Sets the given stack trace element with the given StackFrameInfo
554 */
555 private static native void initStackTraceElement(StackTraceElement element,
556 StackFrameInfo sfi);
557
558 private static final long serialVersionUID = 6992337162326171013L;
559 }
560