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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    * 
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   * 
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.apache.commons.lang3.exception;
18  
19  import java.io.PrintStream;
20  import java.io.PrintWriter;
21  import java.io.StringWriter;
22  import java.lang.reflect.InvocationTargetException;
23  import java.lang.reflect.Method;
24  import java.util.ArrayList;
25  import java.util.List;
26  import java.util.StringTokenizer;
27  
28  import org.apache.commons.lang3.ArrayUtils;
29  import org.apache.commons.lang3.ClassUtils;
30  import org.apache.commons.lang3.StringUtils;
31  import org.apache.commons.lang3.SystemUtils;
32  
33  /**
34   * <p>Provides utilities for manipulating and examining 
35   * <code>Throwable</code> objects.</p>
36   *
37   * @since 1.0
38   * @version $Id: ExceptionUtils.java 1436770 2013-01-22 07:09:45Z ggregory $
39   */
40  public class ExceptionUtils {
41      
42      /**
43       * <p>Used when printing stack frames to denote the start of a
44       * wrapped exception.</p>
45       *
46       * <p>Package private for accessibility by test suite.</p>
47       */
48      static final String WRAPPED_MARKER = " [wrapped] ";
49  
50      /**
51       * <p>The names of methods commonly used to access a wrapped exception.</p>
52       */
53      // TODO: Remove in Lang 4.0
54      private static final String[] CAUSE_METHOD_NAMES = {
55          "getCause",
56          "getNextException",
57          "getTargetException",
58          "getException",
59          "getSourceException",
60          "getRootCause",
61          "getCausedByException",
62          "getNested",
63          "getLinkedException",
64          "getNestedException",
65          "getLinkedCause",
66          "getThrowable",
67      };
68  
69      /**
70       * <p>
71       * Public constructor allows an instance of <code>ExceptionUtils</code> to be created, although that is not
72       * normally necessary.
73       * </p>
74       */
75      public ExceptionUtils() {
76          super();
77      }
78  
79      //-----------------------------------------------------------------------
80      /**
81       * <p>Returns the default names used when searching for the cause of an exception.</p>
82       *
83       * <p>This may be modified and used in the overloaded getCause(Throwable, String[]) method.</p>
84       *
85       * @return cloned array of the default method names
86       * @since 3.0
87       * @deprecated This feature will be removed in Lang 4.0
88       */
89      @Deprecated
90      public static String[] getDefaultCauseMethodNames() {
91          return ArrayUtils.clone(CAUSE_METHOD_NAMES);
92      }
93  
94      //-----------------------------------------------------------------------
95      /**
96       * <p>Introspects the <code>Throwable</code> to obtain the cause.</p>
97       *
98       * <p>The method searches for methods with specific names that return a 
99       * <code>Throwable</code> object. This will pick up most wrapping exceptions,
100      * including those from JDK 1.4.
101      *
102      * <p>The default list searched for are:</p>
103      * <ul>
104      *  <li><code>getCause()</code></li>
105      *  <li><code>getNextException()</code></li>
106      *  <li><code>getTargetException()</code></li>
107      *  <li><code>getException()</code></li>
108      *  <li><code>getSourceException()</code></li>
109      *  <li><code>getRootCause()</code></li>
110      *  <li><code>getCausedByException()</code></li>
111      *  <li><code>getNested()</code></li>
112      * </ul>
113      * 
114      * <p>If none of the above is found, returns <code>null</code>.</p>
115      *
116      * @param throwable  the throwable to introspect for a cause, may be null
117      * @return the cause of the <code>Throwable</code>,
118      *  <code>null</code> if none found or null throwable input
119      * @since 1.0
120      * @deprecated This feature will be removed in Lang 4.0
121      */
122     @Deprecated
123     public static Throwable getCause(final Throwable throwable) {
124         return getCause(throwable, CAUSE_METHOD_NAMES);
125     }
126 
127     /**
128      * <p>Introspects the <code>Throwable</code> to obtain the cause.</p>
129      *
130      * <p>A <code>null</code> set of method names means use the default set.
131      * A <code>null</code> in the set of method names will be ignored.</p>
132      *
133      * @param throwable  the throwable to introspect for a cause, may be null
134      * @param methodNames  the method names, null treated as default set
135      * @return the cause of the <code>Throwable</code>,
136      *  <code>null</code> if none found or null throwable input
137      * @since 1.0
138      * @deprecated This feature will be removed in Lang 4.0
139      */
140     @Deprecated
141     public static Throwable getCause(final Throwable throwable, String[] methodNames) {
142         if (throwable == null) {
143             return null;
144         }
145 
146         if (methodNames == null) {
147             methodNames = CAUSE_METHOD_NAMES;
148         }
149 
150         for (final String methodName : methodNames) {
151             if (methodName != null) {
152                 final Throwable cause = getCauseUsingMethodName(throwable, methodName);
153                 if (cause != null) {
154                     return cause;
155                 }
156             }
157         }
158 
159         return null;
160     }
161 
162     /**
163      * <p>Introspects the <code>Throwable</code> to obtain the root cause.</p>
164      *
165      * <p>This method walks through the exception chain to the last element,
166      * "root" of the tree, using {@link #getCause(Throwable)}, and
167      * returns that exception.</p>
168      *
169      * <p>From version 2.2, this method handles recursive cause structures
170      * that might otherwise cause infinite loops. If the throwable parameter
171      * has a cause of itself, then null will be returned. If the throwable
172      * parameter cause chain loops, the last element in the chain before the
173      * loop is returned.</p>
174      *
175      * @param throwable  the throwable to get the root cause for, may be null
176      * @return the root cause of the <code>Throwable</code>,
177      *  <code>null</code> if none found or null throwable input
178      */
179     public static Throwable getRootCause(final Throwable throwable) {
180         final List<Throwable> list = getThrowableList(throwable);
181         return list.size() < 2 ? null : (Throwable)list.get(list.size() - 1);
182     }
183 
184     /**
185      * <p>Finds a <code>Throwable</code> by method name.</p>
186      *
187      * @param throwable  the exception to examine
188      * @param methodName  the name of the method to find and invoke
189      * @return the wrapped exception, or <code>null</code> if not found
190      */
191     // TODO: Remove in Lang 4.0
192     private static Throwable getCauseUsingMethodName(final Throwable throwable, final String methodName) {
193         Method method = null;
194         try {
195             method = throwable.getClass().getMethod(methodName);
196         } catch (final NoSuchMethodException ignored) { // NOPMD
197             // exception ignored
198         } catch (final SecurityException ignored) { // NOPMD
199             // exception ignored
200         }
201 
202         if (method != null && Throwable.class.isAssignableFrom(method.getReturnType())) {
203             try {
204                 return (Throwable) method.invoke(throwable);
205             } catch (final IllegalAccessException ignored) { // NOPMD
206                 // exception ignored
207             } catch (final IllegalArgumentException ignored) { // NOPMD
208                 // exception ignored
209             } catch (final InvocationTargetException ignored) { // NOPMD
210                 // exception ignored
211             }
212         }
213         return null;
214     }
215 
216     //-----------------------------------------------------------------------
217     /**
218      * <p>Counts the number of <code>Throwable</code> objects in the
219      * exception chain.</p>
220      *
221      * <p>A throwable without cause will return <code>1</code>.
222      * A throwable with one cause will return <code>2</code> and so on.
223      * A <code>null</code> throwable will return <code>0</code>.</p>
224      *
225      * <p>From version 2.2, this method handles recursive cause structures
226      * that might otherwise cause infinite loops. The cause chain is
227      * processed until the end is reached, or until the next item in the
228      * chain is already in the result set.</p>
229      *
230      * @param throwable  the throwable to inspect, may be null
231      * @return the count of throwables, zero if null input
232      */
233     public static int getThrowableCount(final Throwable throwable) {
234         return getThrowableList(throwable).size();
235     }
236 
237     /**
238      * <p>Returns the list of <code>Throwable</code> objects in the
239      * exception chain.</p>
240      *
241      * <p>A throwable without cause will return an array containing
242      * one element - the input throwable.
243      * A throwable with one cause will return an array containing
244      * two elements. - the input throwable and the cause throwable.
245      * A <code>null</code> throwable will return an array of size zero.</p>
246      *
247      * <p>From version 2.2, this method handles recursive cause structures
248      * that might otherwise cause infinite loops. The cause chain is
249      * processed until the end is reached, or until the next item in the
250      * chain is already in the result set.</p>
251      *
252      * @see #getThrowableList(Throwable)
253      * @param throwable  the throwable to inspect, may be null
254      * @return the array of throwables, never null
255      */
256     public static Throwable[] getThrowables(final Throwable throwable) {
257         final List<Throwable> list = getThrowableList(throwable);
258         return list.toArray(new Throwable[list.size()]);
259     }
260 
261     /**
262      * <p>Returns the list of <code>Throwable</code> objects in the
263      * exception chain.</p>
264      *
265      * <p>A throwable without cause will return a list containing
266      * one element - the input throwable.
267      * A throwable with one cause will return a list containing
268      * two elements. - the input throwable and the cause throwable.
269      * A <code>null</code> throwable will return a list of size zero.</p>
270      *
271      * <p>This method handles recursive cause structures that might
272      * otherwise cause infinite loops. The cause chain is processed until
273      * the end is reached, or until the next item in the chain is already
274      * in the result set.</p>
275      *
276      * @param throwable  the throwable to inspect, may be null
277      * @return the list of throwables, never null
278      * @since Commons Lang 2.2
279      */
280     public static List<Throwable> getThrowableList(Throwable throwable) {
281         final List<Throwable> list = new ArrayList<Throwable>();
282         while (throwable != null && list.contains(throwable) == false) {
283             list.add(throwable);
284             throwable = ExceptionUtils.getCause(throwable);
285         }
286         return list;
287     }
288 
289     //-----------------------------------------------------------------------
290     /**
291      * <p>Returns the (zero based) index of the first <code>Throwable</code>
292      * that matches the specified class (exactly) in the exception chain.
293      * Subclasses of the specified class do not match - see
294      * {@link #indexOfType(Throwable, Class)} for the opposite.</p>
295      *
296      * <p>A <code>null</code> throwable returns <code>-1</code>.
297      * A <code>null</code> type returns <code>-1</code>.
298      * No match in the chain returns <code>-1</code>.</p>
299      *
300      * @param throwable  the throwable to inspect, may be null
301      * @param clazz  the class to search for, subclasses do not match, null returns -1
302      * @return the index into the throwable chain, -1 if no match or null input
303      */
304     public static int indexOfThrowable(final Throwable throwable, final Class<?> clazz) {
305         return indexOf(throwable, clazz, 0, false);
306     }
307 
308     /**
309      * <p>Returns the (zero based) index of the first <code>Throwable</code>
310      * that matches the specified type in the exception chain from
311      * a specified index.
312      * Subclasses of the specified class do not match - see
313      * {@link #indexOfType(Throwable, Class, int)} for the opposite.</p>
314      *
315      * <p>A <code>null</code> throwable returns <code>-1</code>.
316      * A <code>null</code> type returns <code>-1</code>.
317      * No match in the chain returns <code>-1</code>.
318      * A negative start index is treated as zero.
319      * A start index greater than the number of throwables returns <code>-1</code>.</p>
320      *
321      * @param throwable  the throwable to inspect, may be null
322      * @param clazz  the class to search for, subclasses do not match, null returns -1
323      * @param fromIndex  the (zero based) index of the starting position,
324      *  negative treated as zero, larger than chain size returns -1
325      * @return the index into the throwable chain, -1 if no match or null input
326      */
327     public static int indexOfThrowable(final Throwable throwable, final Class<?> clazz, final int fromIndex) {
328         return indexOf(throwable, clazz, fromIndex, false);
329     }
330 
331     //-----------------------------------------------------------------------
332     /**
333      * <p>Returns the (zero based) index of the first <code>Throwable</code>
334      * that matches the specified class or subclass in the exception chain.
335      * Subclasses of the specified class do match - see
336      * {@link #indexOfThrowable(Throwable, Class)} for the opposite.</p>
337      *
338      * <p>A <code>null</code> throwable returns <code>-1</code>.
339      * A <code>null</code> type returns <code>-1</code>.
340      * No match in the chain returns <code>-1</code>.</p>
341      *
342      * @param throwable  the throwable to inspect, may be null
343      * @param type  the type to search for, subclasses match, null returns -1
344      * @return the index into the throwable chain, -1 if no match or null input
345      * @since 2.1
346      */
347     public static int indexOfType(final Throwable throwable, final Class<?> type) {
348         return indexOf(throwable, type, 0, true);
349     }
350 
351     /**
352      * <p>Returns the (zero based) index of the first <code>Throwable</code>
353      * that matches the specified type in the exception chain from
354      * a specified index.
355      * Subclasses of the specified class do match - see
356      * {@link #indexOfThrowable(Throwable, Class)} for the opposite.</p>
357      *
358      * <p>A <code>null</code> throwable returns <code>-1</code>.
359      * A <code>null</code> type returns <code>-1</code>.
360      * No match in the chain returns <code>-1</code>.
361      * A negative start index is treated as zero.
362      * A start index greater than the number of throwables returns <code>-1</code>.</p>
363      *
364      * @param throwable  the throwable to inspect, may be null
365      * @param type  the type to search for, subclasses match, null returns -1
366      * @param fromIndex  the (zero based) index of the starting position,
367      *  negative treated as zero, larger than chain size returns -1
368      * @return the index into the throwable chain, -1 if no match or null input
369      * @since 2.1
370      */
371     public static int indexOfType(final Throwable throwable, final Class<?> type, final int fromIndex) {
372         return indexOf(throwable, type, fromIndex, true);
373     }
374 
375     /**
376      * <p>Worker method for the <code>indexOfType</code> methods.</p>
377      *
378      * @param throwable  the throwable to inspect, may be null
379      * @param type  the type to search for, subclasses match, null returns -1
380      * @param fromIndex  the (zero based) index of the starting position,
381      *  negative treated as zero, larger than chain size returns -1
382      * @param subclass if <code>true</code>, compares with {@link Class#isAssignableFrom(Class)}, otherwise compares
383      * using references
384      * @return index of the <code>type</code> within throwables nested within the specified <code>throwable</code>
385      */
386     private static int indexOf(final Throwable throwable, final Class<?> type, int fromIndex, final boolean subclass) {
387         if (throwable == null || type == null) {
388             return -1;
389         }
390         if (fromIndex < 0) {
391             fromIndex = 0;
392         }
393         final Throwable[] throwables = ExceptionUtils.getThrowables(throwable);
394         if (fromIndex >= throwables.length) {
395             return -1;
396         }
397         if (subclass) {
398             for (int i = fromIndex; i < throwables.length; i++) {
399                 if (type.isAssignableFrom(throwables[i].getClass())) {
400                     return i;
401                 }
402             }
403         } else {
404             for (int i = fromIndex; i < throwables.length; i++) {
405                 if (type.equals(throwables[i].getClass())) {
406                     return i;
407                 }
408             }
409         }
410         return -1;
411     }
412 
413     //-----------------------------------------------------------------------
414     /**
415      * <p>Prints a compact stack trace for the root cause of a throwable
416      * to <code>System.err</code>.</p>
417      *
418      * <p>The compact stack trace starts with the root cause and prints
419      * stack frames up to the place where it was caught and wrapped.
420      * Then it prints the wrapped exception and continues with stack frames
421      * until the wrapper exception is caught and wrapped again, etc.</p>
422      *
423      * <p>The output of this method is consistent across JDK versions.
424      * Note that this is the opposite order to the JDK1.4 display.</p>
425      *
426      * <p>The method is equivalent to <code>printStackTrace</code> for throwables
427      * that don't have nested causes.</p>
428      *
429      * @param throwable  the throwable to output
430      * @since 2.0
431      */
432     public static void printRootCauseStackTrace(final Throwable throwable) {
433         printRootCauseStackTrace(throwable, System.err);
434     }
435 
436     /**
437      * <p>Prints a compact stack trace for the root cause of a throwable.</p>
438      *
439      * <p>The compact stack trace starts with the root cause and prints
440      * stack frames up to the place where it was caught and wrapped.
441      * Then it prints the wrapped exception and continues with stack frames
442      * until the wrapper exception is caught and wrapped again, etc.</p>
443      *
444      * <p>The output of this method is consistent across JDK versions.
445      * Note that this is the opposite order to the JDK1.4 display.</p>
446      *
447      * <p>The method is equivalent to <code>printStackTrace</code> for throwables
448      * that don't have nested causes.</p>
449      *
450      * @param throwable  the throwable to output, may be null
451      * @param stream  the stream to output to, may not be null
452      * @throws IllegalArgumentException if the stream is <code>null</code>
453      * @since 2.0
454      */
455     public static void printRootCauseStackTrace(final Throwable throwable, final PrintStream stream) {
456         if (throwable == null) {
457             return;
458         }
459         if (stream == null) {
460             throw new IllegalArgumentException("The PrintStream must not be null");
461         }
462         final String trace[] = getRootCauseStackTrace(throwable);
463         for (final String element : trace) {
464             stream.println(element);
465         }
466         stream.flush();
467     }
468 
469     /**
470      * <p>Prints a compact stack trace for the root cause of a throwable.</p>
471      *
472      * <p>The compact stack trace starts with the root cause and prints
473      * stack frames up to the place where it was caught and wrapped.
474      * Then it prints the wrapped exception and continues with stack frames
475      * until the wrapper exception is caught and wrapped again, etc.</p>
476      *
477      * <p>The output of this method is consistent across JDK versions.
478      * Note that this is the opposite order to the JDK1.4 display.</p>
479      *
480      * <p>The method is equivalent to <code>printStackTrace</code> for throwables
481      * that don't have nested causes.</p>
482      *
483      * @param throwable  the throwable to output, may be null
484      * @param writer  the writer to output to, may not be null
485      * @throws IllegalArgumentException if the writer is <code>null</code>
486      * @since 2.0
487      */
488     public static void printRootCauseStackTrace(final Throwable throwable, final PrintWriter writer) {
489         if (throwable == null) {
490             return;
491         }
492         if (writer == null) {
493             throw new IllegalArgumentException("The PrintWriter must not be null");
494         }
495         final String trace[] = getRootCauseStackTrace(throwable);
496         for (final String element : trace) {
497             writer.println(element);
498         }
499         writer.flush();
500     }
501 
502     //-----------------------------------------------------------------------
503     /**
504      * <p>Creates a compact stack trace for the root cause of the supplied
505      * <code>Throwable</code>.</p>
506      *
507      * <p>The output of this method is consistent across JDK versions.
508      * It consists of the root exception followed by each of its wrapping
509      * exceptions separated by '[wrapped]'. Note that this is the opposite
510      * order to the JDK1.4 display.</p>
511      *
512      * @param throwable  the throwable to examine, may be null
513      * @return an array of stack trace frames, never null
514      * @since 2.0
515      */
516     public static String[] getRootCauseStackTrace(final Throwable throwable) {
517         if (throwable == null) {
518             return ArrayUtils.EMPTY_STRING_ARRAY;
519         }
520         final Throwable throwables[] = getThrowables(throwable);
521         final int count = throwables.length;
522         final List<String> frames = new ArrayList<String>();
523         List<String> nextTrace = getStackFrameList(throwables[count - 1]);
524         for (int i = count; --i >= 0;) {
525             final List<String> trace = nextTrace;
526             if (i != 0) {
527                 nextTrace = getStackFrameList(throwables[i - 1]);
528                 removeCommonFrames(trace, nextTrace);
529             }
530             if (i == count - 1) {
531                 frames.add(throwables[i].toString());
532             } else {
533                 frames.add(WRAPPED_MARKER + throwables[i].toString());
534             }
535             for (int j = 0; j < trace.size(); j++) {
536                 frames.add(trace.get(j));
537             }
538         }
539         return frames.toArray(new String[frames.size()]);
540     }
541 
542     /**
543      * <p>Removes common frames from the cause trace given the two stack traces.</p>
544      *
545      * @param causeFrames  stack trace of a cause throwable
546      * @param wrapperFrames  stack trace of a wrapper throwable
547      * @throws IllegalArgumentException if either argument is null
548      * @since 2.0
549      */
550     public static void removeCommonFrames(final List<String> causeFrames, final List<String> wrapperFrames) {
551         if (causeFrames == null || wrapperFrames == null) {
552             throw new IllegalArgumentException("The List must not be null");
553         }
554         int causeFrameIndex = causeFrames.size() - 1;
555         int wrapperFrameIndex = wrapperFrames.size() - 1;
556         while (causeFrameIndex >= 0 && wrapperFrameIndex >= 0) {
557             // Remove the frame from the cause trace if it is the same
558             // as in the wrapper trace
559             final String causeFrame = causeFrames.get(causeFrameIndex);
560             final String wrapperFrame = wrapperFrames.get(wrapperFrameIndex);
561             if (causeFrame.equals(wrapperFrame)) {
562                 causeFrames.remove(causeFrameIndex);
563             }
564             causeFrameIndex--;
565             wrapperFrameIndex--;
566         }
567     }
568 
569     //-----------------------------------------------------------------------
570     /**
571      * <p>Gets the stack trace from a Throwable as a String.</p>
572      *
573      * <p>The result of this method vary by JDK version as this method
574      * uses {@link Throwable#printStackTrace(java.io.PrintWriter)}.
575      * On JDK1.3 and earlier, the cause exception will not be shown
576      * unless the specified throwable alters printStackTrace.</p>
577      *
578      * @param throwable  the <code>Throwable</code> to be examined
579      * @return the stack trace as generated by the exception's
580      *  <code>printStackTrace(PrintWriter)</code> method
581      */
582     public static String getStackTrace(final Throwable throwable) {
583         final StringWriter sw = new StringWriter();
584         final PrintWriter pw = new PrintWriter(sw, true);
585         throwable.printStackTrace(pw);
586         return sw.getBuffer().toString();
587     }
588 
589     /**
590      * <p>Captures the stack trace associated with the specified
591      * <code>Throwable</code> object, decomposing it into a list of
592      * stack frames.</p>
593      *
594      * <p>The result of this method vary by JDK version as this method
595      * uses {@link Throwable#printStackTrace(java.io.PrintWriter)}.
596      * On JDK1.3 and earlier, the cause exception will not be shown
597      * unless the specified throwable alters printStackTrace.</p>
598      *
599      * @param throwable  the <code>Throwable</code> to examine, may be null
600      * @return an array of strings describing each stack frame, never null
601      */
602     public static String[] getStackFrames(final Throwable throwable) {
603         if (throwable == null) {
604             return ArrayUtils.EMPTY_STRING_ARRAY;
605         }
606         return getStackFrames(getStackTrace(throwable));
607     }
608 
609     //-----------------------------------------------------------------------
610     /**
611      * <p>Returns an array where each element is a line from the argument.</p>
612      *
613      * <p>The end of line is determined by the value of {@link SystemUtils#LINE_SEPARATOR}.</p>
614      *
615      * @param stackTrace  a stack trace String
616      * @return an array where each element is a line from the argument
617      */
618     static String[] getStackFrames(final String stackTrace) {
619         final String linebreak = SystemUtils.LINE_SEPARATOR;
620         final StringTokenizer frames = new StringTokenizer(stackTrace, linebreak);
621         final List<String> list = new ArrayList<String>();
622         while (frames.hasMoreTokens()) {
623             list.add(frames.nextToken());
624         }
625         return list.toArray(new String[list.size()]);
626     }
627 
628     /**
629      * <p>Produces a <code>List</code> of stack frames - the message
630      * is not included. Only the trace of the specified exception is
631      * returned, any caused by trace is stripped.</p>
632      *
633      * <p>This works in most cases - it will only fail if the exception
634      * message contains a line that starts with:
635      * <code>&quot;&nbsp;&nbsp;&nbsp;at&quot;.</code></p>
636      * 
637      * @param t is any throwable
638      * @return List of stack frames
639      */
640     static List<String> getStackFrameList(final Throwable t) {
641         final String stackTrace = getStackTrace(t);
642         final String linebreak = SystemUtils.LINE_SEPARATOR;
643         final StringTokenizer frames = new StringTokenizer(stackTrace, linebreak);
644         final List<String> list = new ArrayList<String>();
645         boolean traceStarted = false;
646         while (frames.hasMoreTokens()) {
647             final String token = frames.nextToken();
648             // Determine if the line starts with <whitespace>at
649             final int at = token.indexOf("at");
650             if (at != -1 && token.substring(0, at).trim().isEmpty()) {
651                 traceStarted = true;
652                 list.add(token);
653             } else if (traceStarted) {
654                 break;
655             }
656         }
657         return list;
658     }
659 
660     //-----------------------------------------------------------------------
661     /**
662      * Gets a short message summarising the exception.
663      * <p>
664      * The message returned is of the form
665      * {ClassNameWithoutPackage}: {ThrowableMessage}
666      *
667      * @param th  the throwable to get a message for, null returns empty string
668      * @return the message, non-null
669      * @since Commons Lang 2.2
670      */
671     public static String getMessage(final Throwable th) {
672         if (th == null) {
673             return "";
674         }
675         final String clsName = ClassUtils.getShortClassName(th, null);
676         final String msg = th.getMessage();
677         return clsName + ": " + StringUtils.defaultString(msg);
678     }
679 
680     //-----------------------------------------------------------------------
681     /**
682      * Gets a short message summarising the root cause exception.
683      * <p>
684      * The message returned is of the form
685      * {ClassNameWithoutPackage}: {ThrowableMessage}
686      *
687      * @param th  the throwable to get a message for, null returns empty string
688      * @return the message, non-null
689      * @since Commons Lang 2.2
690      */
691     public static String getRootCauseMessage(final Throwable th) {
692         Throwable root = ExceptionUtils.getRootCause(th);
693         root = root == null ? th : root;
694         return getMessage(root);
695     }
696 
697 }