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