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.lang.reflect.Layer;
37 import java.lang.reflect.Module;
38 import java.util.HashSet;
39 import java.util.Objects;
40 import java.util.Optional;
41 import java.util.Set;
42
43 /**
44 * An element in a stack trace, as returned by {@link
45 * Throwable#getStackTrace()}. Each element represents a single stack frame.
46 * All stack frames except for the one at the top of the stack represent
47 * a method invocation. The frame at the top of the stack represents the
48 * execution point at which the stack trace was generated. Typically,
49 * this is the point at which the throwable corresponding to the stack trace
50 * was created.
51 *
52 * @since 1.4
53 * @author Josh Bloch
54 */
55 public final class StackTraceElement implements java.io.Serializable {
56
57 // For Throwables and StackWalker, the VM initially sets this field to a
58 // reference to the declaring Class. The Class reference is used to
59 // construct the 'format' bitmap, and then is cleared.
60 //
61 // For STEs constructed using the public constructors, this field is not used.
62 private transient Class<?> declaringClassObject;
63
64 // Normally initialized by VM
65 private String classLoaderName;
66 private String moduleName;
67 private String moduleVersion;
68 private String declaringClass;
69 private String methodName;
70 private String fileName;
71 private int lineNumber;
72 private byte format = 0; // Default to show all
73
74 /**
75 * Creates a stack trace element representing the specified execution
76 * point. The {@link #getModuleName module name} and {@link
77 * #getModuleVersion module version} of the stack trace element will
78 * be {@code null}.
79 *
80 * @param declaringClass the fully qualified name of the class containing
81 * the execution point represented by the stack trace element
82 * @param methodName the name of the method containing the execution point
83 * represented by the stack trace element
84 * @param fileName the name of the file containing the execution point
85 * represented by the stack trace element, or {@code null} if
86 * this information is unavailable
87 * @param lineNumber the line number of the source line containing the
88 * execution point represented by this stack trace element, or
89 * a negative number if this information is unavailable. A value
90 * of -2 indicates that the method containing the execution point
91 * is a native method
92 * @throws NullPointerException if {@code declaringClass} or
93 * {@code methodName} is null
94 * @since 1.5
95 * @revised 9
96 * @spec JPMS
97 */
98 public StackTraceElement(String declaringClass, String methodName,
99 String fileName, int lineNumber) {
100 this(null, null, null, declaringClass, methodName, fileName, lineNumber);
101 }
102
103 /**
104 * Creates a stack trace element representing the specified execution
105 * point.
106 *
107 * @param classLoaderName the class loader name if the class loader of
108 * the class containing the execution point represented by
109 * the stack trace is named; otherwise {@code null}
110 * @param moduleName the module name if the class containing the
111 * execution point represented by the stack trace is in a named
112 * module; otherwise {@code null}
113 * @param moduleVersion the module version if the class containing the
114 * execution point represented by the stack trace is in a named
115 * module that has a version; otherwise {@code null}
116 * @param declaringClass the fully qualified name of the class containing
117 * the execution point represented by the stack trace element
118 * @param methodName the name of the method containing the execution point
119 * represented by the stack trace element
120 * @param fileName the name of the file containing the execution point
121 * represented by the stack trace element, or {@code null} if
122 * this information is unavailable
123 * @param lineNumber the line number of the source line containing the
124 * execution point represented by this stack trace element, or
125 * a negative number if this information is unavailable. A value
126 * of -2 indicates that the method containing the execution point
127 * is a native method
128 *
129 * @throws NullPointerException if {@code declaringClass} is {@code null}
130 * or {@code methodName} is {@code null}
131 *
132 * @since 9
133 * @spec JPMS
134 */
135 public StackTraceElement(String classLoaderName,
136 String moduleName, String moduleVersion,
137 String declaringClass, String methodName,
138 String fileName, int lineNumber) {
139 this.classLoaderName = classLoaderName;
140 this.moduleName = moduleName;
141 this.moduleVersion = moduleVersion;
142 this.declaringClass = Objects.requireNonNull(declaringClass, "Declaring class is null");
143 this.methodName = Objects.requireNonNull(methodName, "Method name is null");
144 this.fileName = fileName;
145 this.lineNumber = lineNumber;
146 }
147
148 /*
149 * Private constructor for the factory methods to create StackTraceElement
150 * for Throwable and StackFrameInfo
151 */
152 private StackTraceElement() {}
153
154 /**
155 * Returns the name of the source file containing the execution point
156 * represented by this stack trace element. Generally, this corresponds
157 * to the {@code SourceFile} attribute of the relevant {@code class}
158 * file (as per <i>The Java Virtual Machine Specification</i>, Section
159 * 4.7.7). In some systems, the name may refer to some source code unit
160 * other than a file, such as an entry in source repository.
161 *
162 * @return the name of the file containing the execution point
163 * represented by this stack trace element, or {@code null} if
164 * this information is unavailable.
165 */
166 public String getFileName() {
167 return fileName;
168 }
169
170 /**
171 * Returns the line number of the source line containing the execution
172 * point represented by this stack trace element. Generally, this is
173 * derived from the {@code LineNumberTable} attribute of the relevant
174 * {@code class} file (as per <i>The Java Virtual Machine
175 * Specification</i>, Section 4.7.8).
176 *
177 * @return the line number of the source line containing the execution
178 * point represented by this stack trace element, or a negative
179 * number if this information is unavailable.
180 */
181 public int getLineNumber() {
182 return lineNumber;
183 }
184
185 /**
186 * Returns the module name of the module containing the execution point
187 * represented by this stack trace element.
188 *
189 * @return the module name of the {@code Module} containing the execution
190 * point represented by this stack trace element; {@code null}
191 * if the module name is not available.
192 * @since 9
193 * @spec JPMS
194 * @see java.lang.reflect.Module#getName()
195 */
196 public String getModuleName() {
197 return moduleName;
198 }
199
200 /**
201 * Returns the module version of the module containing the execution point
202 * represented by this stack trace element.
203 *
204 * @return the module version of the {@code Module} containing the execution
205 * point represented by this stack trace element; {@code null}
206 * if the module version is not available.
207 * @since 9
208 * @spec JPMS
209 * @see java.lang.module.ModuleDescriptor.Version
210 */
211 public String getModuleVersion() {
212 return moduleVersion;
213 }
214
215 /**
216 * Returns the name of the class loader of the class containing the
217 * execution point represented by this stack trace element.
218 *
219 * @return the name of the class loader of the class containing the execution
220 * point represented by this stack trace element; {@code null}
221 * if the class loader is not named.
222 *
223 * @since 9
224 * @spec JPMS
225 * @see java.lang.ClassLoader#getName()
226 */
227 public String getClassLoaderName() {
228 return classLoaderName;
229 }
230
231 /**
232 * Returns the fully qualified name of the class containing the
233 * execution point represented by this stack trace element.
234 *
235 * @return the fully qualified name of the {@code Class} containing
236 * the execution point represented by this stack trace element.
237 */
238 public String getClassName() {
239 return declaringClass;
240 }
241
242 /**
243 * Returns the name of the method containing the execution point
244 * represented by this stack trace element. If the execution point is
245 * contained in an instance or class initializer, this method will return
246 * the appropriate <i>special method name</i>, {@code <init>} or
247 * {@code <clinit>}, as per Section 3.9 of <i>The Java Virtual
248 * Machine Specification</i>.
249 *
250 * @return the name of the method containing the execution point
251 * represented by this stack trace element.
252 */
253 public String getMethodName() {
254 return methodName;
255 }
256
257 /**
258 * Returns true if the method containing the execution point
259 * represented by this stack trace element is a native method.
260 *
261 * @return {@code true} if the method containing the execution point
262 * represented by this stack trace element is a native method.
263 */
264 public boolean isNativeMethod() {
265 return lineNumber == -2;
266 }
267
268 /**
269 * Returns a string representation of this stack trace element.
270 *
271 * @apiNote The format of this string depends on the implementation, but the
272 * following examples may be regarded as typical:
273 * <ul>
274 * <li>
275 * "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Main.java:101)}"
276 * - See the description below.
277 * </li>
278 * <li>
279 * "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Main.java)}"
280 * - The line number is unavailable.
281 * </li>
282 * <li>
283 * "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Unknown Source)}"
284 * - Neither the file name nor the line number is available.
285 * </li>
286 * <li>
287 * "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Native Method)}"
288 * - The method containing the execution point is a native method.
289 * </li>
290 * <li>
291 * "{@code com.foo.loader//com.foo.bar.App.run(App.java:12)}"
292 * - The class of the execution point is defined in the unnamed module of
293 * the class loader named {@code com.foo.loader}.
294 * </li>
295 * <li>
296 * "{@code acme@2.1/org.acme.Lib.test(Lib.java:80)}"
297 * - The class of the execution point is defined in {@code acme} module
298 * loaded by by a built-in class loader such as the application class loader.
299 * </li>
300 * <li>
301 * "{@code MyClass.mash(MyClass.java:9)}"
302 * - {@code MyClass} class is on the application class path.
303 * </li>
304 * </ul>
305 *
306 * <p> The first example shows a stack trace element consisting of
307 * three elements, each separated by {@code "/"} followed with
308 * the source file name and the line number of the source line
309 * containing the execution point.
310 *
311 * The first element "{@code com.foo.loader}" is
312 * the name of the class loader. The second element "{@code foo@9.0}"
313 * is the module name and version. The third element is the method
314 * containing the execution point; "{@code com.foo.Main"}" is the
315 * fully-qualified class name and "{@code run}" is the name of the method.
316 * "{@code Main.java}" is the source file name and "{@code 101}" is
317 * the line number.
318 *
319 * <p> If a class is defined in an <em>unnamed module</em>
320 * then the second element is omitted as shown in
321 * "{@code com.foo.loader//com.foo.bar.App.run(App.java:12)}".
322 *
323 * <p> If the class loader is a <a href="ClassLoader.html#builtinLoaders">
324 * built-in class loader</a> or is not named then the first element
325 * and its following {@code "/"} are omitted as shown in
326 * "{@code acme@2.1/org.acme.Lib.test(Lib.java:80)}".
327 * If the first element is omitted and the module is an unnamed module,
328 * the second element and its following {@code "/"} are also omitted
329 * as shown in "{@code MyClass.mash(MyClass.java:9)}".
330 *
331 * <p> The {@code toString} method may return two different values on two
332 * {@code StackTraceElement} instances that are
333 * {@linkplain #equals(Object) equal}, for example one created via the
334 * constructor, and one obtained from {@link java.lang.Throwable} or
335 * {@link java.lang.StackWalker.StackFrame}, where an implementation may
336 * choose to omit some element in the returned string.
337 *
338 * @revised 9
339 * @spec JPMS
340 * @see Throwable#printStackTrace()
341 */
342 public String toString() {
343 String s = "";
344 if (!dropClassLoaderName() && classLoaderName != null &&
345 !classLoaderName.isEmpty()) {
346 s += classLoaderName + "/";
347 }
348 if (moduleName != null && !moduleName.isEmpty()) {
349 s += moduleName;
350
351 if (!dropModuleVersion() && moduleVersion != null &&
352 !moduleVersion.isEmpty()) {
353 s += "@" + moduleVersion;
354 }
355 }
356 s = s.isEmpty() ? declaringClass : s + "/" + declaringClass;
357
358 return s + "." + methodName + "(" +
359 (isNativeMethod() ? "Native Method)" :
360 (fileName != null && lineNumber >= 0 ?
361 fileName + ":" + lineNumber + ")" :
362 (fileName != null ? ""+fileName+")" : "Unknown Source)")));
363 }
364
365 /**
366 * Returns true if the specified object is another
367 * {@code StackTraceElement} instance representing the same execution
368 * point as this instance. Two stack trace elements {@code a} and
369 * {@code b} are equal if and only if:
370 * <pre>{@code
371 * equals(a.getClassLoaderName(), b.getClassLoaderName()) &&
372 * equals(a.getModuleName(), b.getModuleName()) &&
373 * equals(a.getModuleVersion(), b.getModuleVersion()) &&
374 * equals(a.getClassName(), b.getClassName()) &&
375 * equals(a.getMethodName(), b.getMethodName())
376 * equals(a.getFileName(), b.getFileName()) &&
377 * a.getLineNumber() == b.getLineNumber()
378 *
379 * }</pre>
380 * where {@code equals} has the semantics of {@link
381 * java.util.Objects#equals(Object, Object) Objects.equals}.
382 *
383 * @param obj the object to be compared with this stack trace element.
384 * @return true if the specified object is another
385 * {@code StackTraceElement} instance representing the same
386 * execution point as this instance.
387 *
388 * @revised 9
389 * @spec JPMS
390 */
391 public boolean equals(Object obj) {
392 if (obj==this)
393 return true;
394 if (!(obj instanceof StackTraceElement))
395 return false;
396 StackTraceElement e = (StackTraceElement)obj;
397 return Objects.equals(classLoaderName, e.classLoaderName) &&
398 Objects.equals(moduleName, e.moduleName) &&
399 Objects.equals(moduleVersion, e.moduleVersion) &&
400 e.declaringClass.equals(declaringClass) &&
401 e.lineNumber == lineNumber &&
402 Objects.equals(methodName, e.methodName) &&
403 Objects.equals(fileName, e.fileName);
404 }
405
406 /**
407 * Returns a hash code value for this stack trace element.
408 */
409 public int hashCode() {
410 int result = 31*declaringClass.hashCode() + methodName.hashCode();
411 result = 31*result + Objects.hashCode(classLoaderName);
412 result = 31*result + Objects.hashCode(moduleName);
413 result = 31*result + Objects.hashCode(moduleVersion);
414 result = 31*result + Objects.hashCode(fileName);
415 result = 31*result + lineNumber;
416 return result;
417 }
418
419
420 /**
421 * Called from of() methods to set the 'format' bitmap using the Class
422 * reference stored in declaringClassObject, and then clear the reference.
423 *
424 * <p>
425 * If the module is a non-upgradeable JDK module, then set
426 * JDK_NON_UPGRADEABLE_MODULE to omit its version string.
427 * <p>
428 * If the loader is one of the built-in loaders (`boot`, `platform`, or `app`)
429 * then set BUILTIN_CLASS_LOADER to omit the first element (`<loader>/`).
430 */
431 private synchronized void computeFormat() {
432 try {
433 Class<?> cls = (Class<?>) declaringClassObject;
434 ClassLoader loader = cls.getClassLoader0();
435 Module m = cls.getModule();
436 byte bits = 0;
437
438 // First element - class loader name
439 // Call package-private ClassLoader::name method
440
441 if (loader instanceof BuiltinClassLoader) {
442 bits |= BUILTIN_CLASS_LOADER;
443 }
444
445 // Second element - module name and version
446
447 // Omit if is a JDK non-upgradeable module (recorded in the hashes
448 // in java.base)
449 if (isHashedInJavaBase(m)) {
450 bits |= JDK_NON_UPGRADEABLE_MODULE;
451 }
452 format = bits;
453 } finally {
454 // Class reference no longer needed, clear it
455 declaringClassObject = null;
456 }
457 }
458
459 private static final byte BUILTIN_CLASS_LOADER = 0x1;
460 private static final byte JDK_NON_UPGRADEABLE_MODULE = 0x2;
461
462 private boolean dropClassLoaderName() {
463 return (format & BUILTIN_CLASS_LOADER) == BUILTIN_CLASS_LOADER;
464 }
465
466 private boolean dropModuleVersion() {
467 return (format & JDK_NON_UPGRADEABLE_MODULE) == JDK_NON_UPGRADEABLE_MODULE;
468 }
469
470 /**
471 * Returns true if the module is hashed with java.base.
472 * <p>
473 * This method returns false when running on the exploded image
474 * since JDK modules are not hashed. They have no Version attribute
475 * and so "@<version>" part will be omitted anyway.
476 */
477 private static boolean isHashedInJavaBase(Module m) {
478 // return true if module system is not initialized as the code
479 // must be in java.base
480 if (!VM.isModuleSystemInited())
481 return true;
482
483 return Layer.boot() == m.getLayer() && HashedModules.contains(m);
484 }
485
486 /*
487 * Finds JDK non-upgradeable modules, i.e. the modules that are
488 * included in the hashes in java.base.
489 */
490 private static class HashedModules {
491 static Set<String> HASHED_MODULES = hashedModules();
492
493 static Set<String> hashedModules() {
494
495 Optional<ResolvedModule> resolvedModule = Layer.boot()
496 .configuration()
497 .findModule("java.base");
498 assert resolvedModule.isPresent();
499 ModuleReference mref = resolvedModule.get().reference();
500 assert mref instanceof ModuleReferenceImpl;
501 ModuleHashes hashes = ((ModuleReferenceImpl)mref).recordedHashes();
502 if (hashes != null) {
503 Set<String> names = new HashSet<>(hashes.names());
504 names.add("java.base");
505 return names;
506 }
507
508 return Set.of();
509 }
510
511 static boolean contains(Module m) {
512 return HASHED_MODULES.contains(m.getName());
513 }
514 }
515
516
517 /*
518 * Returns an array of StackTraceElements of the given depth
519 * filled from the backtrace of a given Throwable.
520 */
521 static StackTraceElement[] of(Throwable x, int depth) {
522 StackTraceElement[] stackTrace = new StackTraceElement[depth];
523 for (int i = 0; i < depth; i++) {
524 stackTrace[i] = new StackTraceElement();
525 }
526
527 // VM to fill in StackTraceElement
528 initStackTraceElements(stackTrace, x);
529
530 // ensure the proper StackTraceElement initialization
531 for (StackTraceElement ste : stackTrace) {
532 ste.computeFormat();
533 }
534 return stackTrace;
535 }
536
537 /*
538 * Returns a StackTraceElement from a given StackFrameInfo.
539 */
540 static StackTraceElement of(StackFrameInfo sfi) {
541 StackTraceElement ste = new StackTraceElement();
542 initStackTraceElement(ste, sfi);
543
544 ste.computeFormat();
545 return ste;
546 }
547
548 /*
549 * Sets the given stack trace elements with the backtrace
550 * of the given Throwable.
551 */
552 private static native void initStackTraceElements(StackTraceElement[] elements,
553 Throwable x);
554 /*
555 * Sets the given stack trace element with the given StackFrameInfo
556 */
557 private static native void initStackTraceElement(StackTraceElement element,
558 StackFrameInfo sfi);
559
560 private static final long serialVersionUID = 6992337162326171013L;
561 }