1 /*
2 * Copyright (c) 1994, 2006, 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 import java.io.*;
28 import java.util.*;
29
30 /**
31 * The <code>Throwable</code> class is the superclass of all errors and
32 * exceptions in the Java language. Only objects that are instances of this
33 * class (or one of its subclasses) are thrown by the Java Virtual Machine or
34 * can be thrown by the Java <code>throw</code> statement. Similarly, only
35 * this class or one of its subclasses can be the argument type in a
36 * <code>catch</code> clause.
37 *
38 * For the purposes of compile-time checking of exceptions, {@code
39 * Throwable} and any subclass of {@code Throwable} that is not also a
40 * subclass of either {@link RuntimeException} or {@link Error} are
41 * regarded as checked exceptions.
42 *
43 * <p>Instances of two subclasses, {@link java.lang.Error} and
44 * {@link java.lang.Exception}, are conventionally used to indicate
45 * that exceptional situations have occurred. Typically, these instances
46 * are freshly created in the context of the exceptional situation so
47 * as to include relevant information (such as stack trace data).
48 *
49 * <p>A throwable contains a snapshot of the execution stack of its thread at
50 * the time it was created. It can also contain a message string that gives
51 * more information about the error. Finally, it can contain a <i>cause</i>:
52 * another throwable that caused this throwable to get thrown. The cause
53 * facility is new in release 1.4. It is also known as the <i>chained
54 * exception</i> facility, as the cause can, itself, have a cause, and so on,
55 * leading to a "chain" of exceptions, each caused by another.
56 *
57 * <p>One reason that a throwable may have a cause is that the class that
58 * throws it is built atop a lower layered abstraction, and an operation on
59 * the upper layer fails due to a failure in the lower layer. It would be bad
60 * design to let the throwable thrown by the lower layer propagate outward, as
61 * it is generally unrelated to the abstraction provided by the upper layer.
62 * Further, doing so would tie the API of the upper layer to the details of
63 * its implementation, assuming the lower layer's exception was a checked
64 * exception. Throwing a "wrapped exception" (i.e., an exception containing a
65 * cause) allows the upper layer to communicate the details of the failure to
66 * its caller without incurring either of these shortcomings. It preserves
67 * the flexibility to change the implementation of the upper layer without
68 * changing its API (in particular, the set of exceptions thrown by its
69 * methods).
70 *
71 * <p>A second reason that a throwable may have a cause is that the method
72 * that throws it must conform to a general-purpose interface that does not
73 * permit the method to throw the cause directly. For example, suppose
74 * a persistent collection conforms to the {@link java.util.Collection
75 * Collection} interface, and that its persistence is implemented atop
76 * <tt>java.io</tt>. Suppose the internals of the <tt>add</tt> method
77 * can throw an {@link java.io.IOException IOException}. The implementation
78 * can communicate the details of the <tt>IOException</tt> to its caller
79 * while conforming to the <tt>Collection</tt> interface by wrapping the
80 * <tt>IOException</tt> in an appropriate unchecked exception. (The
81 * specification for the persistent collection should indicate that it is
82 * capable of throwing such exceptions.)
83 *
84 * <p>A cause can be associated with a throwable in two ways: via a
85 * constructor that takes the cause as an argument, or via the
86 * {@link #initCause(Throwable)} method. New throwable classes that
87 * wish to allow causes to be associated with them should provide constructors
88 * that take a cause and delegate (perhaps indirectly) to one of the
89 * <tt>Throwable</tt> constructors that takes a cause. For example:
90 * <pre>
91 * try {
92 * lowLevelOp();
93 * } catch (LowLevelException le) {
94 * throw new HighLevelException(le); // Chaining-aware constructor
95 * }
96 * </pre>
97 * Because the <tt>initCause</tt> method is public, it allows a cause to be
98 * associated with any throwable, even a "legacy throwable" whose
99 * implementation predates the addition of the exception chaining mechanism to
100 * <tt>Throwable</tt>. For example:
101 * <pre>
102 * try {
103 * lowLevelOp();
104 * } catch (LowLevelException le) {
105 * throw (HighLevelException)
106 * new HighLevelException().initCause(le); // Legacy constructor
107 * }
108 * </pre>
109 *
110 * <p>Prior to release 1.4, there were many throwables that had their own
111 * non-standard exception chaining mechanisms (
112 * {@link ExceptionInInitializerError}, {@link ClassNotFoundException},
113 * {@link java.lang.reflect.UndeclaredThrowableException},
114 * {@link java.lang.reflect.InvocationTargetException},
115 * {@link java.io.WriteAbortedException},
116 * {@link java.security.PrivilegedActionException},
117 * {@link java.awt.print.PrinterIOException},
118 * {@link java.rmi.RemoteException} and
119 * {@link javax.naming.NamingException}).
120 * All of these throwables have been retrofitted to
121 * use the standard exception chaining mechanism, while continuing to
122 * implement their "legacy" chaining mechanisms for compatibility.
123 *
124 * <p>Further, as of release 1.4, many general purpose <tt>Throwable</tt>
125 * classes (for example {@link Exception}, {@link RuntimeException},
126 * {@link Error}) have been retrofitted with constructors that take
127 * a cause. This was not strictly necessary, due to the existence of the
128 * <tt>initCause</tt> method, but it is more convenient and expressive to
129 * delegate to a constructor that takes a cause.
130 *
131 * <p>By convention, class <code>Throwable</code> and its subclasses have two
132 * constructors, one that takes no arguments and one that takes a
133 * <code>String</code> argument that can be used to produce a detail message.
134 * Further, those subclasses that might likely have a cause associated with
135 * them should have two more constructors, one that takes a
136 * <code>Throwable</code> (the cause), and one that takes a
137 * <code>String</code> (the detail message) and a <code>Throwable</code> (the
138 * cause).
139 *
140 * <p>Also introduced in release 1.4 is the {@link #getStackTrace()} method,
141 * which allows programmatic access to the stack trace information that was
142 * previously available only in text form, via the various forms of the
143 * {@link #printStackTrace()} method. This information has been added to the
144 * <i>serialized representation</i> of this class so <tt>getStackTrace</tt>
145 * and <tt>printStackTrace</tt> will operate properly on a throwable that
146 * was obtained by deserialization.
147 *
148 * @author unascribed
149 * @author Josh Bloch (Added exception chaining and programmatic access to
150 * stack trace in 1.4.)
151 * @jls3 11.2 Compile-Time Checking of Exceptions
152 * @since JDK1.0
153 */
154 public class Throwable implements Serializable {
155 /** use serialVersionUID from JDK 1.0.2 for interoperability */
156 private static final long serialVersionUID = -3042686055658047285L;
157
158 /**
159 * Native code saves some indication of the stack backtrace in this slot.
160 */
161 private transient Object backtrace;
162
163 /**
164 * Specific details about the Throwable. For example, for
165 * <tt>FileNotFoundException</tt>, this contains the name of
166 * the file that could not be found.
167 *
168 * @serial
169 */
170 private String detailMessage;
171
172 /**
173 * The throwable that caused this throwable to get thrown, or null if this
174 * throwable was not caused by another throwable, or if the causative
175 * throwable is unknown. If this field is equal to this throwable itself,
176 * it indicates that the cause of this throwable has not yet been
177 * initialized.
178 *
179 * @serial
180 * @since 1.4
181 */
182 private Throwable cause = this;
183
184 /**
185 * The stack trace, as returned by {@link #getStackTrace()}.
186 *
187 * @serial
188 * @since 1.4
189 */
190 private StackTraceElement[] stackTrace;
191 /*
192 * This field is lazily initialized on first use or serialization and
193 * nulled out when fillInStackTrace is called.
194 */
195
196 /**
197 * The list of suppressed exceptions, as returned by
198 * {@link #getSuppressedExceptions()}.
199 *
200 * @serial
201 * @since 1.7
202 */
203 private List<Throwable> suppressedExceptions = Collections.emptyList();
204
205 /** Caption for lableing causative exception stack traces */
206 private static final String CAUSE_CAPTION = "Caused by: ";
207
208 /** Caption for lableing suppressed exception stack traces */
209 private static final String SUPPRESSED_CAPTION = "Suppressed: ";
210
211 /**
212 * Constructs a new throwable with <code>null</code> as its detail message.
213 * The cause is not initialized, and may subsequently be initialized by a
214 * call to {@link #initCause}.
215 *
216 * <p>The {@link #fillInStackTrace()} method is called to initialize
217 * the stack trace data in the newly created throwable.
218 */
219 public Throwable() {
220 fillInStackTrace();
221 }
222
223 /**
224 * Constructs a new throwable with the specified detail message. The
225 * cause is not initialized, and may subsequently be initialized by
226 * a call to {@link #initCause}.
227 *
228 * <p>The {@link #fillInStackTrace()} method is called to initialize
229 * the stack trace data in the newly created throwable.
230 *
231 * @param message the detail message. The detail message is saved for
232 * later retrieval by the {@link #getMessage()} method.
233 */
234 public Throwable(String message) {
235 fillInStackTrace();
236 detailMessage = message;
237 }
238
239 /**
240 * Constructs a new throwable with the specified detail message and
241 * cause. <p>Note that the detail message associated with
242 * <code>cause</code> is <i>not</i> automatically incorporated in
243 * this throwable's detail message.
244 *
245 * <p>The {@link #fillInStackTrace()} method is called to initialize
246 * the stack trace data in the newly created throwable.
247 *
248 * @param message the detail message (which is saved for later retrieval
249 * by the {@link #getMessage()} method).
250 * @param cause the cause (which is saved for later retrieval by the
251 * {@link #getCause()} method). (A <tt>null</tt> value is
252 * permitted, and indicates that the cause is nonexistent or
253 * unknown.)
254 * @since 1.4
255 */
256 public Throwable(String message, Throwable cause) {
257 fillInStackTrace();
258 detailMessage = message;
259 this.cause = cause;
260 }
261
262 /**
263 * Constructs a new throwable with the specified cause and a detail
264 * message of <tt>(cause==null ? null : cause.toString())</tt> (which
265 * typically contains the class and detail message of <tt>cause</tt>).
266 * This constructor is useful for throwables that are little more than
267 * wrappers for other throwables (for example, {@link
268 * java.security.PrivilegedActionException}).
269 *
270 * <p>The {@link #fillInStackTrace()} method is called to initialize
271 * the stack trace data in the newly created throwable.
272 *
273 * @param cause the cause (which is saved for later retrieval by the
274 * {@link #getCause()} method). (A <tt>null</tt> value is
275 * permitted, and indicates that the cause is nonexistent or
276 * unknown.)
277 * @since 1.4
278 */
279 public Throwable(Throwable cause) {
280 fillInStackTrace();
281 detailMessage = (cause==null ? null : cause.toString());
282 this.cause = cause;
283 }
284
285 /**
286 * Returns the detail message string of this throwable.
287 *
288 * @return the detail message string of this <tt>Throwable</tt> instance
289 * (which may be <tt>null</tt>).
290 */
291 public String getMessage() {
292 return detailMessage;
293 }
294
295 /**
296 * Creates a localized description of this throwable.
297 * Subclasses may override this method in order to produce a
298 * locale-specific message. For subclasses that do not override this
299 * method, the default implementation returns the same result as
300 * <code>getMessage()</code>.
301 *
302 * @return The localized description of this throwable.
303 * @since JDK1.1
304 */
305 public String getLocalizedMessage() {
306 return getMessage();
307 }
308
309 /**
310 * Returns the cause of this throwable or <code>null</code> if the
311 * cause is nonexistent or unknown. (The cause is the throwable that
312 * caused this throwable to get thrown.)
313 *
314 * <p>This implementation returns the cause that was supplied via one of
315 * the constructors requiring a <tt>Throwable</tt>, or that was set after
316 * creation with the {@link #initCause(Throwable)} method. While it is
317 * typically unnecessary to override this method, a subclass can override
318 * it to return a cause set by some other means. This is appropriate for
319 * a "legacy chained throwable" that predates the addition of chained
320 * exceptions to <tt>Throwable</tt>. Note that it is <i>not</i>
321 * necessary to override any of the <tt>PrintStackTrace</tt> methods,
322 * all of which invoke the <tt>getCause</tt> method to determine the
323 * cause of a throwable.
324 *
325 * @return the cause of this throwable or <code>null</code> if the
326 * cause is nonexistent or unknown.
327 * @since 1.4
328 */
329 public Throwable getCause() {
330 return (cause==this ? null : cause);
331 }
332
333 /**
334 * Initializes the <i>cause</i> of this throwable to the specified value.
335 * (The cause is the throwable that caused this throwable to get thrown.)
336 *
337 * <p>This method can be called at most once. It is generally called from
338 * within the constructor, or immediately after creating the
339 * throwable. If this throwable was created
340 * with {@link #Throwable(Throwable)} or
341 * {@link #Throwable(String,Throwable)}, this method cannot be called
342 * even once.
343 *
344 * @param cause the cause (which is saved for later retrieval by the
345 * {@link #getCause()} method). (A <tt>null</tt> value is
346 * permitted, and indicates that the cause is nonexistent or
347 * unknown.)
348 * @return a reference to this <code>Throwable</code> instance.
349 * @throws IllegalArgumentException if <code>cause</code> is this
350 * throwable. (A throwable cannot be its own cause.)
351 * @throws IllegalStateException if this throwable was
352 * created with {@link #Throwable(Throwable)} or
353 * {@link #Throwable(String,Throwable)}, or this method has already
354 * been called on this throwable.
355 * @since 1.4
356 */
357 public synchronized Throwable initCause(Throwable cause) {
358 if (this.cause != this)
359 throw new IllegalStateException("Can't overwrite cause");
360 if (cause == this)
361 throw new IllegalArgumentException("Self-causation not permitted");
362 this.cause = cause;
363 return this;
364 }
365
366 /**
367 * Returns a short description of this throwable.
368 * The result is the concatenation of:
369 * <ul>
370 * <li> the {@linkplain Class#getName() name} of the class of this object
371 * <li> ": " (a colon and a space)
372 * <li> the result of invoking this object's {@link #getLocalizedMessage}
373 * method
374 * </ul>
375 * If <tt>getLocalizedMessage</tt> returns <tt>null</tt>, then just
376 * the class name is returned.
377 *
378 * @return a string representation of this throwable.
379 */
380 public String toString() {
381 String s = getClass().getName();
382 String message = getLocalizedMessage();
383 return (message != null) ? (s + ": " + message) : s;
384 }
385
386 /**
387 * Prints this throwable and its backtrace to the
388 * standard error stream. This method prints a stack trace for this
389 * <code>Throwable</code> object on the error output stream that is
390 * the value of the field <code>System.err</code>. The first line of
391 * output contains the result of the {@link #toString()} method for
392 * this object. Remaining lines represent data previously recorded by
393 * the method {@link #fillInStackTrace()}. The format of this
394 * information depends on the implementation, but the following
395 * example may be regarded as typical:
396 * <blockquote><pre>
397 * java.lang.NullPointerException
398 * at MyClass.mash(MyClass.java:9)
399 * at MyClass.crunch(MyClass.java:6)
400 * at MyClass.main(MyClass.java:3)
401 * </pre></blockquote>
402 * This example was produced by running the program:
403 * <pre>
404 * class MyClass {
405 * public static void main(String[] args) {
406 * crunch(null);
407 * }
408 * static void crunch(int[] a) {
409 * mash(a);
410 * }
411 * static void mash(int[] b) {
412 * System.out.println(b[0]);
413 * }
414 * }
415 * </pre>
416 * The backtrace for a throwable with an initialized, non-null cause
417 * should generally include the backtrace for the cause. The format
418 * of this information depends on the implementation, but the following
419 * example may be regarded as typical:
420 * <pre>
421 * HighLevelException: MidLevelException: LowLevelException
422 * at Junk.a(Junk.java:13)
423 * at Junk.main(Junk.java:4)
424 * Caused by: MidLevelException: LowLevelException
425 * at Junk.c(Junk.java:23)
426 * at Junk.b(Junk.java:17)
427 * at Junk.a(Junk.java:11)
428 * ... 1 more
429 * Caused by: LowLevelException
430 * at Junk.e(Junk.java:30)
431 * at Junk.d(Junk.java:27)
432 * at Junk.c(Junk.java:21)
433 * ... 3 more
434 * </pre>
435 * Note the presence of lines containing the characters <tt>"..."</tt>.
436 * These lines indicate that the remainder of the stack trace for this
437 * exception matches the indicated number of frames from the bottom of the
438 * stack trace of the exception that was caused by this exception (the
439 * "enclosing" exception). This shorthand can greatly reduce the length
440 * of the output in the common case where a wrapped exception is thrown
441 * from same method as the "causative exception" is caught. The above
442 * example was produced by running the program:
443 * <pre>
444 * public class Junk {
445 * public static void main(String args[]) {
446 * try {
447 * a();
448 * } catch(HighLevelException e) {
449 * e.printStackTrace();
450 * }
451 * }
452 * static void a() throws HighLevelException {
453 * try {
454 * b();
455 * } catch(MidLevelException e) {
456 * throw new HighLevelException(e);
457 * }
458 * }
459 * static void b() throws MidLevelException {
460 * c();
461 * }
462 * static void c() throws MidLevelException {
463 * try {
464 * d();
465 * } catch(LowLevelException e) {
466 * throw new MidLevelException(e);
467 * }
468 * }
469 * static void d() throws LowLevelException {
470 * e();
471 * }
472 * static void e() throws LowLevelException {
473 * throw new LowLevelException();
474 * }
475 * }
476 *
477 * class HighLevelException extends Exception {
478 * HighLevelException(Throwable cause) { super(cause); }
479 * }
480 *
481 * class MidLevelException extends Exception {
482 * MidLevelException(Throwable cause) { super(cause); }
483 * }
484 *
485 * class LowLevelException extends Exception {
486 * }
487 * </pre>
488 * As of release 7, the platform supports the notion of
489 * <i>suppressed exceptions</i> (in conjunction with automatic
490 * resource management blocks). Any exceptions that were
491 * suppressed in order to deliver an exception are printed out
492 * beneath the stack trace. The format of this information
493 * depends on the implementation, but the following example may be
494 * regarded as typical:
495 *
496 * <pre>
497 * Exception in thread "main" java.lang.Exception: Something happened
498 * at Foo.bar(Foo.java:10)
499 * at Foo.main(Foo.java:5)
500 * Suppressed: Resource$CloseFailException: Resource ID = 0
501 * at Resource.close(Resource.java:26)
502 * at Foo.bar(Foo.java:9)
503 * ... 1 more
504 * </pre>
505 * Note that the "... n more" notation is used on suppressed exceptions
506 * just at it is used on causes. Unlike causes, suppressed exceptions are
507 * indented beyond their "containing exceptions."
508 *
509 * <p>An exception can have both a cause and one or more suppressed
510 * exceptions:
511 * <pre>
512 * Exception in thread "main" java.lang.Exception: Main block
513 * at Foo3.main(Foo3.java:7)
514 * Suppressed: Resource$CloseFailException: Resource ID = 2
515 * at Resource.close(Resource.java:26)
516 * at Foo3.main(Foo3.java:5)
517 * Suppressed: Resource$CloseFailException: Resource ID = 1
518 * at Resource.close(Resource.java:26)
519 * at Foo3.main(Foo3.java:5)
520 * Caused by: java.lang.Exception: I did it
521 * at Foo3.main(Foo3.java:8)
522 * </pre>
523 * Likewise, a suppressed exception can have a cause:
524 * <pre>
525 * Exception in thread "main" java.lang.Exception: Main block
526 * at Foo4.main(Foo4.java:6)
527 * Suppressed: Resource2$CloseFailException: Resource ID = 1
528 * at Resource2.close(Resource2.java:20)
529 * at Foo4.main(Foo4.java:5)
530 * Caused by: java.lang.Exception: Rats, you caught me
531 * at Resource2$CloseFailException.<init>(Resource2.java:45)
532 * ... 2 more
533 * </pre>
534 */
535 public void printStackTrace() {
536 printStackTrace(System.err);
537 }
538
539 /**
540 * Prints this throwable and its backtrace to the specified print stream.
541 *
542 * @param s <code>PrintStream</code> to use for output
543 */
544 public void printStackTrace(PrintStream s) {
545 printStackTrace(new WrappedPrintStream(s));
546 }
547
548 private void printStackTrace(PrintStreamOrWriter s) {
549 synchronized (s.lock()) {
550 // Print our stack trace
551 s.println(this);
552 StackTraceElement[] trace = getOurStackTrace();
553 for (StackTraceElement traceElement : trace)
554 s.println("\tat " + traceElement);
555
556 // Print suppressed exceptions, if any
557 for (Throwable se : suppressedExceptions)
558 se.printEnclosedStackTrace(s, trace, SUPPRESSED_CAPTION, "\t");
559
560 // Print cause, if any
561 Throwable ourCause = getCause();
562 if (ourCause != null)
563 ourCause.printEnclosedStackTrace(s, trace, CAUSE_CAPTION, "");
564 }
565 }
566
567 /**
568 * Print our stack trace as an enclosed exception for the specified
569 * stack trace.
570 */
571 private void printEnclosedStackTrace(PrintStreamOrWriter s,
572 StackTraceElement[] enclosingTrace, String caption, String prefix) {
573 assert Thread.holdsLock(s.lock());
574
575 // Compute number of frames in common between this and enclosing trace
576 StackTraceElement[] trace = getOurStackTrace();
577 int m = trace.length-1, n = enclosingTrace.length-1;
578 while (m >= 0 && n >=0 && trace[m].equals(enclosingTrace[n])) {
579 m--; n--;
580 }
581 int framesInCommon = trace.length - 1 - m;
582
583 // Print our stack trace
584 s.println(prefix + caption + this);
585 for (int i = 0; i <= m; i++)
586 s.println(prefix + "\tat " + trace[i]);
587 if (framesInCommon != 0)
588 s.println(prefix + "\t... " + framesInCommon + " more");
589
590 // Print suppressed exceptions, if any
591 for (Throwable se : suppressedExceptions)
592 se.printEnclosedStackTrace(s, trace, SUPPRESSED_CAPTION,
593 prefix +"\t");
594
595 // Print cause, if any
596 Throwable ourCause = getCause();
597 if (ourCause != null)
598 ourCause.printEnclosedStackTrace(s, trace, CAUSE_CAPTION, prefix);
599 }
600
601 /**
602 * Prints this throwable and its backtrace to the specified
603 * print writer.
604 *
605 * @param s <code>PrintWriter</code> to use for output
606 * @since JDK1.1
607 */
608 public void printStackTrace(PrintWriter s) {
609 printStackTrace(new WrappedPrintWriter(s));
610 }
611
612 /**
613 * Wrapper class for PrintStream and PrintWirter to enable a single
614 * implementation of printStackTrace.
615 */
616 private abstract static class PrintStreamOrWriter {
617 /** Returns the object to be locked when using this StreamOrWriter */
618 abstract Object lock();
619
620 /** Prints the specified string as a line on this StreamOrWriter */
621 abstract void println(Object o);
622 }
623
624 private static class WrappedPrintStream extends PrintStreamOrWriter {
625 private final PrintStream printStream;
626
627 WrappedPrintStream(PrintStream printStream) {
628 this.printStream = printStream;
629 }
630
631 Object lock() {
632 return printStream;
633 }
634
635 void println(Object o) {
636 printStream.println(o);
637 }
638 }
639
640 private static class WrappedPrintWriter extends PrintStreamOrWriter {
641 private final PrintWriter printWriter;
642
643 WrappedPrintWriter(PrintWriter printWriter) {
644 this.printWriter = printWriter;
645 }
646
647 Object lock() {
648 return printWriter;
649 }
650
651 void println(Object o) {
652 printWriter.println(o);
653 }
654 }
655
656 /**
657 * Fills in the execution stack trace. This method records within this
658 * <code>Throwable</code> object information about the current state of
659 * the stack frames for the current thread.
660 *
661 * @return a reference to this <code>Throwable</code> instance.
662 * @see java.lang.Throwable#printStackTrace()
663 */
664 public synchronized native Throwable fillInStackTrace();
665
666 /**
667 * Provides programmatic access to the stack trace information printed by
668 * {@link #printStackTrace()}. Returns an array of stack trace elements,
669 * each representing one stack frame. The zeroth element of the array
670 * (assuming the array's length is non-zero) represents the top of the
671 * stack, which is the last method invocation in the sequence. Typically,
672 * this is the point at which this throwable was created and thrown.
673 * The last element of the array (assuming the array's length is non-zero)
674 * represents the bottom of the stack, which is the first method invocation
675 * in the sequence.
676 *
677 * <p>Some virtual machines may, under some circumstances, omit one
678 * or more stack frames from the stack trace. In the extreme case,
679 * a virtual machine that has no stack trace information concerning
680 * this throwable is permitted to return a zero-length array from this
681 * method. Generally speaking, the array returned by this method will
682 * contain one element for every frame that would be printed by
683 * <tt>printStackTrace</tt>.
684 *
685 * @return an array of stack trace elements representing the stack trace
686 * pertaining to this throwable.
687 * @since 1.4
688 */
689 public StackTraceElement[] getStackTrace() {
690 return getOurStackTrace().clone();
691 }
692
693 private synchronized StackTraceElement[] getOurStackTrace() {
694 // Initialize stack trace if this is the first call to this method
695 if (stackTrace == null) {
696 int depth = getStackTraceDepth();
697 stackTrace = new StackTraceElement[depth];
698 for (int i=0; i < depth; i++)
699 stackTrace[i] = getStackTraceElement(i);
700 }
701 return stackTrace;
702 }
703
704 /**
705 * Sets the stack trace elements that will be returned by
706 * {@link #getStackTrace()} and printed by {@link #printStackTrace()}
707 * and related methods.
708 *
709 * This method, which is designed for use by RPC frameworks and other
710 * advanced systems, allows the client to override the default
711 * stack trace that is either generated by {@link #fillInStackTrace()}
712 * when a throwable is constructed or deserialized when a throwable is
713 * read from a serialization stream.
714 *
715 * @param stackTrace the stack trace elements to be associated with
716 * this <code>Throwable</code>. The specified array is copied by this
717 * call; changes in the specified array after the method invocation
718 * returns will have no affect on this <code>Throwable</code>'s stack
719 * trace.
720 *
721 * @throws NullPointerException if <code>stackTrace</code> is
722 * <code>null</code>, or if any of the elements of
723 * <code>stackTrace</code> are <code>null</code>
724 *
725 * @since 1.4
726 */
727 public void setStackTrace(StackTraceElement[] stackTrace) {
728 StackTraceElement[] defensiveCopy = stackTrace.clone();
729 for (int i = 0; i < defensiveCopy.length; i++)
730 if (defensiveCopy[i] == null)
731 throw new NullPointerException("stackTrace[" + i + "]");
732
733 this.stackTrace = defensiveCopy;
734 }
735
736 /**
737 * Returns the number of elements in the stack trace (or 0 if the stack
738 * trace is unavailable).
739 *
740 * package-protection for use by SharedSecrets.
741 */
742 native int getStackTraceDepth();
743
744 /**
745 * Returns the specified element of the stack trace.
746 *
747 * package-protection for use by SharedSecrets.
748 *
749 * @param index index of the element to return.
750 * @throws IndexOutOfBoundsException if <tt>index < 0 ||
751 * index >= getStackTraceDepth() </tt>
752 */
753 native StackTraceElement getStackTraceElement(int index);
754
755 private synchronized void writeObject(java.io.ObjectOutputStream s)
756 throws IOException
757 {
758 getOurStackTrace(); // Ensure that stackTrace field is initialized.
759 s.defaultWriteObject();
760 }
761
762 /**
763 * Adds the specified exception to the list of exceptions that
764 * were suppressed, typically by the automatic resource management
765 * statement, in order to deliver this exception.
766 *
767 * @param exception the exception to be added to the list of
768 * suppressed exceptions
769 * @throws NullPointerException if {@code exception} is null
770 * @since 1.7
771 */
772 public synchronized void addSuppressedException(Throwable exception) {
773 if (exception == null)
774 throw new NullPointerException();
775
776 if (suppressedExceptions.size() == 0)
777 suppressedExceptions = new ArrayList<Throwable>();
778 suppressedExceptions.add(exception);
779 }
780
781 private static final Throwable[] EMPTY_THROWABLE_ARRAY = new Throwable[0];
782
783 /**
784 * Returns an array containing all of the exceptions that were
785 * suppressed, typically by the automatic resource management
786 * statement, in order to deliver this exception.
787 *
788 * @return an array containing all of the exceptions that were
789 * suppressed to deliver this exception.
790 * @since 1.7
791 */
792 public Throwable[] getSuppressedExceptions() {
793 return suppressedExceptions.toArray(EMPTY_THROWABLE_ARRAY);
794 }
795 }