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