1 /*
2 * Copyright (c) 2015, 2017, 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
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23 * questions.
24 */
25 package java.lang;
26
27 import jdk.internal.reflect.CallerSensitive;
28
29 import java.lang.invoke.MethodType;
30 import java.util.EnumSet;
31 import java.util.Objects;
32 import java.util.Set;
33 import java.util.function.Consumer;
34 import java.util.function.Function;
35 import java.util.stream.Stream;
36
37 /**
38 * A stack walker.
39 *
40 * <p> The {@link StackWalker#walk walk} method opens a sequential stream
41 * of {@link StackFrame StackFrame}s for the current thread and then applies
42 * the given function to walk the {@code StackFrame} stream.
43 * The stream reports stack frame elements in order, from the top most frame
44 * that represents the execution point at which the stack was generated to
45 * the bottom most frame.
46 * The {@code StackFrame} stream is closed when the {@code walk} method returns.
47 * If an attempt is made to reuse the closed stream,
48 * {@code IllegalStateException} will be thrown.
49 *
50 * <p> The {@linkplain Option <em>stack walking options</em>} of a
51 * {@code StackWalker} determines the information of
52 * {@link StackFrame StackFrame} objects to be returned.
53 * By default, stack frames of the reflection API and implementation
54 * classes are {@linkplain Option#SHOW_HIDDEN_FRAMES hidden}
55 * and {@code StackFrame}s have the class name and method name
56 * available but not the {@link StackFrame#getDeclaringClass() Class reference}.
57 *
58 * <p> {@code StackWalker} is thread-safe. Multiple threads can share
59 * a single {@code StackWalker} object to traverse its own stack.
60 * A permission check is performed when a {@code StackWalker} is created,
61 * according to the options it requests.
62 * No further permission check is done at stack walking time.
63 *
64 * @apiNote
65 * Examples
66 *
67 * <p>1. To find the first caller filtering a known list of implementation class:
68 * <pre>{@code
69 * StackWalker walker = StackWalker.getInstance(Option.RETAIN_CLASS_REFERENCE);
70 * Optional<Class<?>> callerClass = walker.walk(s ->
71 * s.map(StackFrame::getDeclaringClass)
72 * .filter(interestingClasses::contains)
73 * .findFirst());
74 * }</pre>
75 *
76 * <p>2. To snapshot the top 10 stack frames of the current thread,
77 * <pre>{@code
78 * List<StackFrame> stack = StackWalker.getInstance().walk(s ->
79 * s.limit(10).collect(Collectors.toList()));
80 * }</pre>
81 *
82 * Unless otherwise noted, passing a {@code null} argument to a
83 * constructor or method in this {@code StackWalker} class
84 * will cause a {@link NullPointerException NullPointerException}
85 * to be thrown.
86 *
87 * @since 9
88 */
89 public final class StackWalker {
90 /**
91 * A {@code StackFrame} object represents a method invocation returned by
92 * {@link StackWalker}.
93 *
94 * <p> The {@link #getDeclaringClass()} method may be unsupported as determined
95 * by the {@linkplain Option stack walking options} of a {@linkplain
96 * StackWalker stack walker}.
97 *
98 * @since 9
99 * @jvms 2.6
100 */
101 public interface StackFrame {
102 /**
103 * Gets the <a href="ClassLoader.html#binary-name">binary name</a>
104 * of the declaring class of the method represented by this stack frame.
105 *
106 * @return the binary name of the declaring class of the method
107 * represented by this stack frame
108 *
109 * @jls 13.1 The Form of a Binary
110 */
111 public String getClassName();
112
113 /**
114 * Gets the name of the method represented by this stack frame.
115 * @return the name of the method represented by this stack frame
116 */
117 public String getMethodName();
118
119 /**
120 * Gets the declaring {@code Class} for the method represented by
121 * this stack frame.
122 *
123 * @return the declaring {@code Class} of the method represented by
124 * this stack frame
125 *
126 * @throws UnsupportedOperationException if this {@code StackWalker}
127 * is not configured with {@link Option#RETAIN_CLASS_REFERENCE
128 * Option.RETAIN_CLASS_REFERENCE}.
129 */
130 public Class<?> getDeclaringClass();
131
132 /**
133 * Returns the {@link MethodType} representing the parameter types and
134 * the return type for the method represented by this stack frame.
135 *
136 * @implSpec
137 * The default implementation throws {@code UnsupportedOperationException}.
138 *
139 * @return the {@code MethodType} for this stack frame
140 *
141 * @throws UnsupportedOperationException if this {@code StackWalker}
142 * is not configured with {@link Option#RETAIN_CLASS_REFERENCE
143 * Option.RETAIN_CLASS_REFERENCE}.
144 *
145 * @since 10
146 */
147 public default MethodType getMethodType() {
148 throw new UnsupportedOperationException();
149 }
150
151 /**
152 * Returns the <i>descriptor</i> of the method represented by
153 * this stack frame as defined by
154 * <cite>The Java Virtual Machine Specification</cite>.
155 *
156 * @implSpec
157 * The default implementation throws {@code UnsupportedOperationException}.
158 *
159 * @return the descriptor of the method represented by
160 * this stack frame
161 *
162 * @see MethodType#fromMethodDescriptorString(String, ClassLoader)
163 * @see MethodType#toMethodDescriptorString()
164 * @jvms 4.3.3 Method Descriptor
165 *
166 * @since 10
167 */
168 public default String getDescriptor() {
169 throw new UnsupportedOperationException();
170 }
171
172
173 /**
174 * Returns the index to the code array of the {@code Code} attribute
175 * containing the execution point represented by this stack frame.
176 * The code array gives the actual bytes of Java Virtual Machine code
177 * that implement the method.
178 *
179 * @return the index to the code array of the {@code Code} attribute
180 * containing the execution point represented by this stack frame,
181 * or a negative number if the method is native.
182 *
183 * @jvms 4.7.3 The {@code Code} Attribute
184 */
185 public int getByteCodeIndex();
186
187 /**
188 * Returns the name of the source file containing the execution point
189 * represented by this stack frame. Generally, this corresponds
190 * to the {@code SourceFile} attribute of the relevant {@code class}
191 * file as defined by <cite>The Java Virtual Machine Specification</cite>.
192 * In some systems, the name may refer to some source code unit
193 * other than a file, such as an entry in a source repository.
194 *
195 * @return the name of the file containing the execution point
196 * represented by this stack frame, or {@code null} if
197 * this information is unavailable.
198 *
199 * @jvms 4.7.10 The {@code SourceFile} Attribute
200 */
201 public String getFileName();
202
203 /**
204 * Returns the line number of the source line containing the execution
205 * point represented by this stack frame. Generally, this is
206 * derived from the {@code LineNumberTable} attribute of the relevant
207 * {@code class} file as defined by <cite>The Java Virtual Machine
208 * Specification</cite>.
209 *
210 * @return the line number of the source line containing the execution
211 * point represented by this stack frame, or a negative number if
212 * this information is unavailable.
213 *
214 * @jvms 4.7.12 The {@code LineNumberTable} Attribute
215 */
216 public int getLineNumber();
217
218 /**
219 * Returns {@code true} if the method containing the execution point
220 * represented by this stack frame is a native method.
221 *
222 * @return {@code true} if the method containing the execution point
223 * represented by this stack frame is a native method.
224 */
225 public boolean isNativeMethod();
226
227 /**
228 * Gets a {@code StackTraceElement} for this stack frame.
229 *
230 * @return {@code StackTraceElement} for this stack frame.
231 */
232 public StackTraceElement toStackTraceElement();
233 }
234
235 /**
236 * Stack walker option to configure the {@linkplain StackFrame stack frame}
237 * information obtained by a {@code StackWalker}.
238 *
239 * @since 9
240 */
241 public enum Option {
242 /**
243 * Retains {@code Class} object in {@code StackFrame}s
244 * walked by this {@code StackWalker}.
245 *
246 * <p> A {@code StackWalker} configured with this option will support
247 * {@link StackWalker#getCallerClass()} and
248 * {@link StackFrame#getDeclaringClass() StackFrame.getDeclaringClass()}.
249 */
250 RETAIN_CLASS_REFERENCE,
251 /**
252 * Shows all reflection frames.
253 *
254 * <p>By default, reflection frames are hidden. A {@code StackWalker}
255 * configured with this {@code SHOW_REFLECT_FRAMES} option
256 * will show all reflection frames that
257 * include {@link java.lang.reflect.Method#invoke} and
258 * {@link java.lang.reflect.Constructor#newInstance(Object...)}
259 * and their reflection implementation classes.
260 *
261 * <p>The {@link #SHOW_HIDDEN_FRAMES} option can also be used to show all
262 * reflection frames and it will also show other hidden frames that
263 * are implementation-specific.
264 *
265 * @apiNote
266 * This option includes the stack frames representing the invocation of
267 * {@code Method} and {@code Constructor}. Any utility methods that
268 * are equivalent to calling {@code Method.invoke} or
269 * {@code Constructor.newInstance} such as {@code Class.newInstance}
270 * are not filtered or controlled by any stack walking option.
271 */
272 SHOW_REFLECT_FRAMES,
273 /**
274 * Shows all hidden frames.
275 *
276 * <p>A Java Virtual Machine implementation may hide implementation
277 * specific frames in addition to {@linkplain #SHOW_REFLECT_FRAMES
278 * reflection frames}. A {@code StackWalker} with this {@code SHOW_HIDDEN_FRAMES}
279 * option will show all hidden frames (including reflection frames).
280 */
281 SHOW_HIDDEN_FRAMES;
282 }
283
284 enum ExtendedOption {
285 /**
286 * Obtain monitors, locals and operands.
287 */
288 LOCALS_AND_OPERANDS
289 };
290
291 static final EnumSet<Option> DEFAULT_EMPTY_OPTION = EnumSet.noneOf(Option.class);
292
293 private final static StackWalker DEFAULT_WALKER =
294 new StackWalker(DEFAULT_EMPTY_OPTION);
295
296 private final Set<Option> options;
297 private final ExtendedOption extendedOption;
298 private final int estimateDepth;
299 final boolean retainClassRef; // cached for performance
300
301 /**
302 * Returns a {@code StackWalker} instance.
303 *
304 * <p> This {@code StackWalker} is configured to skip all
305 * {@linkplain Option#SHOW_HIDDEN_FRAMES hidden frames} and
306 * no {@linkplain Option#RETAIN_CLASS_REFERENCE class reference} is retained.
307 *
308 * @return a {@code StackWalker} configured to skip all
309 * {@linkplain Option#SHOW_HIDDEN_FRAMES hidden frames} and
310 * no {@linkplain Option#RETAIN_CLASS_REFERENCE class reference} is retained.
311 *
312 */
313 public static StackWalker getInstance() {
314 // no permission check needed
315 return DEFAULT_WALKER;
316 }
317
318 /**
319 * Returns a {@code StackWalker} instance with the given option specifying
320 * the stack frame information it can access.
321 *
322 * <p>
323 * If a security manager is present and the given {@code option} is
324 * {@link Option#RETAIN_CLASS_REFERENCE Option.RETAIN_CLASS_REFERENCE},
325 * it calls its {@link SecurityManager#checkPermission checkPermission}
326 * method for {@code RuntimePermission("getStackWalkerWithClassReference")}.
327 *
328 * @param option {@link Option stack walking option}
329 *
330 * @return a {@code StackWalker} configured with the given option
331 *
332 * @throws SecurityException if a security manager exists and its
333 * {@code checkPermission} method denies access.
334 */
335 public static StackWalker getInstance(Option option) {
336 return getInstance(EnumSet.of(Objects.requireNonNull(option)));
337 }
338
339 /**
340 * Returns a {@code StackWalker} instance with the given {@code options} specifying
341 * the stack frame information it can access. If the given {@code options}
342 * is empty, this {@code StackWalker} is configured to skip all
343 * {@linkplain Option#SHOW_HIDDEN_FRAMES hidden frames} and no
344 * {@linkplain Option#RETAIN_CLASS_REFERENCE class reference} is retained.
345 *
346 * <p>
347 * If a security manager is present and the given {@code options} contains
348 * {@link Option#RETAIN_CLASS_REFERENCE Option.RETAIN_CLASS_REFERENCE},
349 * it calls its {@link SecurityManager#checkPermission checkPermission}
350 * method for {@code RuntimePermission("getStackWalkerWithClassReference")}.
351 *
352 * @param options {@link Option stack walking option}
353 *
354 * @return a {@code StackWalker} configured with the given options
355 *
356 * @throws SecurityException if a security manager exists and its
357 * {@code checkPermission} method denies access.
358 */
359 public static StackWalker getInstance(Set<Option> options) {
360 if (options.isEmpty()) {
361 return DEFAULT_WALKER;
362 }
363
364 EnumSet<Option> optionSet = toEnumSet(options);
365 checkPermission(optionSet);
366 return new StackWalker(optionSet);
367 }
368
369 /**
370 * Returns a {@code StackWalker} instance with the given {@code options} specifying
371 * the stack frame information it can access. If the given {@code options}
372 * is empty, this {@code StackWalker} is configured to skip all
373 * {@linkplain Option#SHOW_HIDDEN_FRAMES hidden frames} and no
374 * {@linkplain Option#RETAIN_CLASS_REFERENCE class reference} is retained.
375 *
376 * <p>
377 * If a security manager is present and the given {@code options} contains
378 * {@link Option#RETAIN_CLASS_REFERENCE Option.RETAIN_CLASS_REFERENCE},
379 * it calls its {@link SecurityManager#checkPermission checkPermission}
380 * method for {@code RuntimePermission("getStackWalkerWithClassReference")}.
381 *
382 * <p>
383 * The {@code estimateDepth} specifies the estimate number of stack frames
384 * this {@code StackWalker} will traverse that the {@code StackWalker} could
385 * use as a hint for the buffer size.
386 *
387 * @param options {@link Option stack walking options}
388 * @param estimateDepth Estimate number of stack frames to be traversed.
389 *
390 * @return a {@code StackWalker} configured with the given options
391 *
392 * @throws IllegalArgumentException if {@code estimateDepth <= 0}
393 * @throws SecurityException if a security manager exists and its
394 * {@code checkPermission} method denies access.
395 */
396 public static StackWalker getInstance(Set<Option> options, int estimateDepth) {
397 if (estimateDepth <= 0) {
398 throw new IllegalArgumentException("estimateDepth must be > 0");
399 }
400 EnumSet<Option> optionSet = toEnumSet(options);
401 checkPermission(optionSet);
402 return new StackWalker(optionSet, estimateDepth);
403 }
404
405 // ----- private constructors ------
406 private StackWalker(EnumSet<Option> options) {
407 this(options, 0, null);
408 }
409 private StackWalker(EnumSet<Option> options, int estimateDepth) {
410 this(options, estimateDepth, null);
411 }
412 private StackWalker(EnumSet<Option> options, int estimateDepth, ExtendedOption extendedOption) {
413 this.options = options;
414 this.estimateDepth = estimateDepth;
415 this.extendedOption = extendedOption;
416 this.retainClassRef = hasOption(Option.RETAIN_CLASS_REFERENCE);
417 }
418
419 private static void checkPermission(Set<Option> options) {
420 Objects.requireNonNull(options);
421 SecurityManager sm = System.getSecurityManager();
422 if (sm != null) {
423 if (options.contains(Option.RETAIN_CLASS_REFERENCE)) {
424 sm.checkPermission(new RuntimePermission("getStackWalkerWithClassReference"));
425 }
426 }
427 }
428
429 /*
430 * Returns a defensive copy
431 */
432 private static EnumSet<Option> toEnumSet(Set<Option> options) {
433 Objects.requireNonNull(options);
434 if (options.isEmpty()) {
435 return DEFAULT_EMPTY_OPTION;
436 } else {
437 return EnumSet.copyOf(options);
438 }
439 }
440
441 /**
442 * Applies the given function to the stream of {@code StackFrame}s
443 * for the current thread, traversing from the top frame of the stack,
444 * which is the method calling this {@code walk} method.
445 *
446 * <p>The {@code StackFrame} stream will be closed when
447 * this method returns. When a closed {@code Stream<StackFrame>} object
448 * is reused, {@code IllegalStateException} will be thrown.
449 *
450 * @apiNote
451 * For example, to find the first 10 calling frames, first skipping those frames
452 * whose declaring class is in package {@code com.foo}:
453 * <blockquote>
454 * <pre>{@code
455 * List<StackFrame> frames = StackWalker.getInstance().walk(s ->
456 * s.dropWhile(f -> f.getClassName().startsWith("com.foo."))
457 * .limit(10)
458 * .collect(Collectors.toList()));
459 * }</pre></blockquote>
460 *
461 * <p>This method takes a {@code Function} accepting a {@code Stream<StackFrame>},
462 * rather than returning a {@code Stream<StackFrame>} and allowing the
463 * caller to directly manipulate the stream. The Java virtual machine is
464 * free to reorganize a thread's control stack, for example, via
465 * deoptimization. By taking a {@code Function} parameter, this method
466 * allows access to stack frames through a stable view of a thread's control
467 * stack.
468 *
469 * <p>Parallel execution is effectively disabled and stream pipeline
470 * execution will only occur on the current thread.
471 *
472 * @implNote The implementation stabilizes the stack by anchoring a frame
473 * specific to the stack walking and ensures that the stack walking is
474 * performed above the anchored frame. When the stream object is closed or
475 * being reused, {@code IllegalStateException} will be thrown.
476 *
477 * @param function a function that takes a stream of
478 * {@linkplain StackFrame stack frames} and returns a result.
479 * @param <T> The type of the result of applying the function to the
480 * stream of {@linkplain StackFrame stack frame}.
481 *
482 * @return the result of applying the function to the stream of
483 * {@linkplain StackFrame stack frame}.
484 */
485 @CallerSensitive
486 public <T> T walk(Function<? super Stream<StackFrame>, ? extends T> function) {
487 // Returning a Stream<StackFrame> would be unsafe, as the stream could
488 // be used to access the stack frames in an uncontrolled manner. For
489 // example, a caller might pass a Spliterator of stack frames after one
490 // or more frames had been traversed. There is no robust way to detect
491 // whether the execution point when
492 // Spliterator.tryAdvance(java.util.function.Consumer<? super T>) is
493 // invoked is the exact same execution point where the stack frame
494 // traversal is expected to resume.
495
496 Objects.requireNonNull(function);
497 return StackStreamFactory.makeStackTraverser(this, function)
498 .walk();
499 }
500
501 /**
502 * Performs the given action on each element of {@code StackFrame} stream
503 * of the current thread, traversing from the top frame of the stack,
504 * which is the method calling this {@code forEach} method.
505 *
506 * <p> This method is equivalent to calling
507 * <blockquote>
508 * {@code walk(s -> { s.forEach(action); return null; });}
509 * </blockquote>
510 *
511 * @param action an action to be performed on each {@code StackFrame}
512 * of the stack of the current thread
513 */
514 @CallerSensitive
515 public void forEach(Consumer<? super StackFrame> action) {
516 Objects.requireNonNull(action);
517 StackStreamFactory.makeStackTraverser(this, s -> {
518 s.forEach(action);
519 return null;
520 }).walk();
521 }
522
523 /**
524 * Gets the {@code Class} object of the caller who invoked the method
525 * that invoked {@code getCallerClass}.
526 *
527 * <p> This method filters {@linkplain Option#SHOW_REFLECT_FRAMES reflection
528 * frames}, {@link java.lang.invoke.MethodHandle}, and
529 * {@linkplain Option#SHOW_HIDDEN_FRAMES hidden frames} regardless of the
530 * {@link Option#SHOW_REFLECT_FRAMES SHOW_REFLECT_FRAMES}
531 * and {@link Option#SHOW_HIDDEN_FRAMES SHOW_HIDDEN_FRAMES} options
532 * this {@code StackWalker} has been configured with.
533 *
534 * <p> This method should be called when a caller frame is present. If
535 * it is called from the bottom most frame on the stack,
536 * {@code IllegalCallerException} will be thrown.
537 *
538 * <p> This method throws {@code UnsupportedOperationException}
539 * if this {@code StackWalker} is not configured with the
540 * {@link Option#RETAIN_CLASS_REFERENCE RETAIN_CLASS_REFERENCE} option.
541 *
542 * @apiNote
543 * For example, {@code Util::getResourceBundle} loads a resource bundle
544 * on behalf of the caller. It invokes {@code getCallerClass} to identify
545 * the class whose method called {@code Util::getResourceBundle}.
546 * Then, it obtains the class loader of that class, and uses
547 * the class loader to load the resource bundle. The caller class
548 * in this example is {@code MyTool}.
549 *
550 * <pre>{@code
551 * class Util {
552 * private final StackWalker walker = StackWalker.getInstance(Option.RETAIN_CLASS_REFERENCE);
553 * public ResourceBundle getResourceBundle(String bundleName) {
554 * Class<?> caller = walker.getCallerClass();
555 * return ResourceBundle.getBundle(bundleName, Locale.getDefault(), caller.getClassLoader());
556 * }
557 * }
558 *
559 * class MyTool {
560 * private final Util util = new Util();
561 * private void init() {
562 * ResourceBundle rb = util.getResourceBundle("mybundle");
563 * }
564 * }
565 * }</pre>
566 *
567 * An equivalent way to find the caller class using the
568 * {@link StackWalker#walk walk} method is as follows
569 * (filtering the reflection frames, {@code MethodHandle} and hidden frames
570 * not shown below):
571 * <pre>{@code
572 * Optional<Class<?>> caller = walker.walk(s ->
573 * s.map(StackFrame::getDeclaringClass)
574 * .skip(2)
575 * .findFirst());
576 * }</pre>
577 *
578 * When the {@code getCallerClass} method is called from a method that
579 * is the bottom most frame on the stack,
580 * for example, {@code static public void main} method launched by the
581 * {@code java} launcher, or a method invoked from a JNI attached thread,
582 * {@code IllegalCallerException} is thrown.
583 *
584 * @return {@code Class} object of the caller's caller invoking this method.
585 *
586 * @throws UnsupportedOperationException if this {@code StackWalker}
587 * is not configured with {@link Option#RETAIN_CLASS_REFERENCE
588 * Option.RETAIN_CLASS_REFERENCE}.
589 * @throws IllegalCallerException if there is no caller frame, i.e.
590 * when this {@code getCallerClass} method is called from a method
591 * which is the last frame on the stack.
592 */
593 @CallerSensitive
594 public Class<?> getCallerClass() {
595 if (!retainClassRef) {
596 throw new UnsupportedOperationException("This stack walker " +
597 "does not have RETAIN_CLASS_REFERENCE access");
598 }
599
600 return StackStreamFactory.makeCallerFinder(this).findCaller();
601 }
602
603 // ---- package access ----
604
605 static StackWalker newInstance(Set<Option> options, ExtendedOption extendedOption) {
606 EnumSet<Option> optionSet = toEnumSet(options);
607 checkPermission(optionSet);
608 return new StackWalker(optionSet, 0, extendedOption);
609 }
610
611 int estimateDepth() {
612 return estimateDepth;
613 }
614
615 boolean hasOption(Option option) {
616 return options.contains(option);
617 }
618
619 boolean hasLocalsOperandsOption() {
620 return extendedOption == ExtendedOption.LOCALS_AND_OPERANDS;
621 }
622 }