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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.lang.reflect.UndeclaredThrowableException;
25  import java.util.ArrayList;
26  import java.util.List;
27  import java.util.StringTokenizer;
28  
29  import org.apache.commons.lang3.ArrayUtils;
30  import org.apache.commons.lang3.ClassUtils;
31  import org.apache.commons.lang3.StringUtils;
32  import org.apache.commons.lang3.Validate;
33  
34  /**
35   * <p>Provides utilities for manipulating and examining
36   * <code>Throwable</code> objects.</p>
37   *
38   * @since 1.0
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, use {@link Throwable#getCause} instead
121      */
122     @Deprecated
123     public static Throwable getCause(final Throwable throwable) {
124         return getCause(throwable, null);
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, use {@link Throwable#getCause} instead
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             final Throwable cause = throwable.getCause();
148             if (cause != null) {
149                 return cause;
150             }
151 
152             methodNames = CAUSE_METHOD_NAMES;
153         }
154 
155         for (final String methodName : methodNames) {
156             if (methodName != null) {
157                 final Throwable legacyCause = getCauseUsingMethodName(throwable, methodName);
158                 if (legacyCause != null) {
159                     return legacyCause;
160                 }
161             }
162         }
163 
164         return null;
165     }
166 
167     /**
168      * <p>Introspects the <code>Throwable</code> to obtain the root cause.</p>
169      *
170      * <p>This method walks through the exception chain to the last element,
171      * "root" of the tree, using {@link #getCause(Throwable)}, and
172      * returns that exception.</p>
173      *
174      * <p>From version 2.2, this method handles recursive cause structures
175      * that might otherwise cause infinite loops. If the throwable parameter
176      * has a cause of itself, then null will be returned. If the throwable
177      * parameter cause chain loops, the last element in the chain before the
178      * loop is returned.</p>
179      *
180      * @param throwable  the throwable to get the root cause for, may be null
181      * @return the root cause of the <code>Throwable</code>,
182      *  <code>null</code> if none found or null throwable input
183      */
184     public static Throwable getRootCause(final Throwable throwable) {
185         final List<Throwable> list = getThrowableList(throwable);
186         return list.size() < 2 ? null : list.get(list.size() - 1);
187     }
188 
189     /**
190      * <p>Finds a <code>Throwable</code> by method name.</p>
191      *
192      * @param throwable  the exception to examine
193      * @param methodName  the name of the method to find and invoke
194      * @return the wrapped exception, or <code>null</code> if not found
195      */
196     // TODO: Remove in Lang 4.0
197     private static Throwable getCauseUsingMethodName(final Throwable throwable, final String methodName) {
198         Method method = null;
199         try {
200             method = throwable.getClass().getMethod(methodName);
201         } catch (final NoSuchMethodException | SecurityException ignored) { // NOPMD
202             // exception ignored
203         }
204 
205         if (method != null && Throwable.class.isAssignableFrom(method.getReturnType())) {
206             try {
207                 return (Throwable) method.invoke(throwable);
208             } catch (final IllegalAccessException | IllegalArgumentException | InvocationTargetException ignored) { // NOPMD
209                 // exception ignored
210             }
211         }
212         return null;
213     }
214 
215     //-----------------------------------------------------------------------
216     /**
217      * <p>Counts the number of <code>Throwable</code> objects in the
218      * exception chain.</p>
219      *
220      * <p>A throwable without cause will return <code>1</code>.
221      * A throwable with one cause will return <code>2</code> and so on.
222      * A <code>null</code> throwable will return <code>0</code>.</p>
223      *
224      * <p>From version 2.2, this method handles recursive cause structures
225      * that might otherwise cause infinite loops. The cause chain is
226      * processed until the end is reached, or until the next item in the
227      * chain is already in the result set.</p>
228      *
229      * @param throwable  the throwable to inspect, may be null
230      * @return the count of throwables, zero if null input
231      */
232     public static int getThrowableCount(final Throwable throwable) {
233         return getThrowableList(throwable).size();
234     }
235 
236     /**
237      * <p>Returns the list of <code>Throwable</code> objects in the
238      * exception chain.</p>
239      *
240      * <p>A throwable without cause will return an array containing
241      * one element - the input throwable.
242      * A throwable with one cause will return an array containing
243      * two elements. - the input throwable and the cause throwable.
244      * A <code>null</code> throwable will return an array of size zero.</p>
245      *
246      * <p>From version 2.2, this method handles recursive cause structures
247      * that might otherwise cause infinite loops. The cause chain is
248      * processed until the end is reached, or until the next item in the
249      * chain is already in the result set.</p>
250      *
251      * @see #getThrowableList(Throwable)
252      * @param throwable  the throwable to inspect, may be null
253      * @return the array of throwables, never null
254      */
255     public static Throwable[] getThrowables(final Throwable throwable) {
256         final List<Throwable> list = getThrowableList(throwable);
257         return list.toArray(new Throwable[list.size()]);
258     }
259 
260     /**
261      * <p>Returns the list of <code>Throwable</code> objects in the
262      * exception chain.</p>
263      *
264      * <p>A throwable without cause will return a list containing
265      * one element - the input throwable.
266      * A throwable with one cause will return a list containing
267      * two elements. - the input throwable and the cause throwable.
268      * A <code>null</code> throwable will return a list of size zero.</p>
269      *
270      * <p>This method handles recursive cause structures that might
271      * otherwise cause infinite loops. The cause chain is processed until
272      * the end is reached, or until the next item in the chain is already
273      * in the result set.</p>
274      *
275      * @param throwable  the throwable to inspect, may be null
276      * @return the list of throwables, never null
277      * @since Commons Lang 2.2
278      */
279     public static List<Throwable> getThrowableList(Throwable throwable) {
280         final List<Throwable> list = new ArrayList<>();
281         while (throwable != null && list.contains(throwable) == false) {
282             list.add(throwable);
283             throwable = ExceptionUtils.getCause(throwable);
284         }
285         return list;
286     }
287 
288     //-----------------------------------------------------------------------
289     /**
290      * <p>Returns the (zero based) index of the first <code>Throwable</code>
291      * that matches the specified class (exactly) in the exception chain.
292      * Subclasses of the specified class do not match - see
293      * {@link #indexOfType(Throwable, Class)} for the opposite.</p>
294      *
295      * <p>A <code>null</code> throwable returns <code>-1</code>.
296      * A <code>null</code> type returns <code>-1</code>.
297      * No match in the chain returns <code>-1</code>.</p>
298      *
299      * @param throwable  the throwable to inspect, may be null
300      * @param clazz  the class to search for, subclasses do not match, null returns -1
301      * @return the index into the throwable chain, -1 if no match or null input
302      */
303     public static int indexOfThrowable(final Throwable throwable, final Class<?> clazz) {
304         return indexOf(throwable, clazz, 0, false);
305     }
306 
307     /**
308      * <p>Returns the (zero based) index of the first <code>Throwable</code>
309      * that matches the specified type in the exception chain from
310      * a specified index.
311      * Subclasses of the specified class do not match - see
312      * {@link #indexOfType(Throwable, Class, int)} for the opposite.</p>
313      *
314      * <p>A <code>null</code> throwable returns <code>-1</code>.
315      * A <code>null</code> type returns <code>-1</code>.
316      * No match in the chain returns <code>-1</code>.
317      * A negative start index is treated as zero.
318      * A start index greater than the number of throwables returns <code>-1</code>.</p>
319      *
320      * @param throwable  the throwable to inspect, may be null
321      * @param clazz  the class to search for, subclasses do not match, null returns -1
322      * @param fromIndex  the (zero based) index of the starting position,
323      *  negative treated as zero, larger than chain size returns -1
324      * @return the index into the throwable chain, -1 if no match or null input
325      */
326     public static int indexOfThrowable(final Throwable throwable, final Class<?> clazz, final int fromIndex) {
327         return indexOf(throwable, clazz, fromIndex, false);
328     }
329 
330     //-----------------------------------------------------------------------
331     /**
332      * <p>Returns the (zero based) index of the first <code>Throwable</code>
333      * that matches the specified class or subclass in the exception chain.
334      * Subclasses of the specified class do match - see
335      * {@link #indexOfThrowable(Throwable, Class)} for the opposite.</p>
336      *
337      * <p>A <code>null</code> throwable returns <code>-1</code>.
338      * A <code>null</code> type returns <code>-1</code>.
339      * No match in the chain returns <code>-1</code>.</p>
340      *
341      * @param throwable  the throwable to inspect, may be null
342      * @param type  the type to search for, subclasses match, null returns -1
343      * @return the index into the throwable chain, -1 if no match or null input
344      * @since 2.1
345      */
346     public static int indexOfType(final Throwable throwable, final Class<?> type) {
347         return indexOf(throwable, type, 0, true);
348     }
349 
350     /**
351      * <p>Returns the (zero based) index of the first <code>Throwable</code>
352      * that matches the specified type in the exception chain from
353      * a specified index.
354      * Subclasses of the specified class do match - see
355      * {@link #indexOfThrowable(Throwable, Class)} for the opposite.</p>
356      *
357      * <p>A <code>null</code> throwable returns <code>-1</code>.
358      * A <code>null</code> type returns <code>-1</code>.
359      * No match in the chain returns <code>-1</code>.
360      * A negative start index is treated as zero.
361      * A start index greater than the number of throwables returns <code>-1</code>.</p>
362      *
363      * @param throwable  the throwable to inspect, may be null
364      * @param type  the type to search for, subclasses match, null returns -1
365      * @param fromIndex  the (zero based) index of the starting position,
366      *  negative treated as zero, larger than chain size returns -1
367      * @return the index into the throwable chain, -1 if no match or null input
368      * @since 2.1
369      */
370     public static int indexOfType(final Throwable throwable, final Class<?> type, final int fromIndex) {
371         return indexOf(throwable, type, fromIndex, true);
372     }
373 
374     /**
375      * <p>Worker method for the <code>indexOfType</code> methods.</p>
376      *
377      * @param throwable  the throwable to inspect, may be null
378      * @param type  the type to search for, subclasses match, null returns -1
379      * @param fromIndex  the (zero based) index of the starting position,
380      *  negative treated as zero, larger than chain size returns -1
381      * @param subclass if <code>true</code>, compares with {@link Class#isAssignableFrom(Class)}, otherwise compares
382      * using references
383      * @return index of the <code>type</code> within throwables nested within the specified <code>throwable</code>
384      */
385     private static int indexOf(final Throwable throwable, final Class<?> type, int fromIndex, final boolean subclass) {
386         if (throwable == null || type == null) {
387             return -1;
388         }
389         if (fromIndex < 0) {
390             fromIndex = 0;
391         }
392         final Throwable[] throwables = ExceptionUtils.getThrowables(throwable);
393         if (fromIndex >= throwables.length) {
394             return -1;
395         }
396         if (subclass) {
397             for (int i = fromIndex; i < throwables.length; i++) {
398                 if (type.isAssignableFrom(throwables[i].getClass())) {
399                     return i;
400                 }
401             }
402         } else {
403             for (int i = fromIndex; i < throwables.length; i++) {
404                 if (type.equals(throwables[i].getClass())) {
405                     return i;
406                 }
407             }
408         }
409         return -1;
410     }
411 
412     //-----------------------------------------------------------------------
413     /**
414      * <p>Prints a compact stack trace for the root cause of a throwable
415      * to <code>System.err</code>.</p>
416      *
417      * <p>The compact stack trace starts with the root cause and prints
418      * stack frames up to the place where it was caught and wrapped.
419      * Then it prints the wrapped exception and continues with stack frames
420      * until the wrapper exception is caught and wrapped again, etc.</p>
421      *
422      * <p>The output of this method is consistent across JDK versions.
423      * Note that this is the opposite order to the JDK1.4 display.</p>
424      *
425      * <p>The method is equivalent to <code>printStackTrace</code> for throwables
426      * that don't have nested causes.</p>
427      *
428      * @param throwable  the throwable to output
429      * @since 2.0
430      */
431     public static void printRootCauseStackTrace(final Throwable throwable) {
432         printRootCauseStackTrace(throwable, System.err);
433     }
434 
435     /**
436      * <p>Prints a compact stack trace for the root cause of a throwable.</p>
437      *
438      * <p>The compact stack trace starts with the root cause and prints
439      * stack frames up to the place where it was caught and wrapped.
440      * Then it prints the wrapped exception and continues with stack frames
441      * until the wrapper exception is caught and wrapped again, etc.</p>
442      *
443      * <p>The output of this method is consistent across JDK versions.
444      * Note that this is the opposite order to the JDK1.4 display.</p>
445      *
446      * <p>The method is equivalent to <code>printStackTrace</code> for throwables
447      * that don't have nested causes.</p>
448      *
449      * @param throwable  the throwable to output, may be null
450      * @param stream  the stream to output to, may not be null
451      * @throws IllegalArgumentException if the stream is <code>null</code>
452      * @since 2.0
453      */
454     public static void printRootCauseStackTrace(final Throwable throwable, final PrintStream stream) {
455         if (throwable == null) {
456             return;
457         }
458         Validate.isTrue(stream != null, "The PrintStream must not be null");
459         final String trace[] = getRootCauseStackTrace(throwable);
460         for (final String element : trace) {
461             stream.println(element);
462         }
463         stream.flush();
464     }
465 
466     /**
467      * <p>Prints a compact stack trace for the root cause of a throwable.</p>
468      *
469      * <p>The compact stack trace starts with the root cause and prints
470      * stack frames up to the place where it was caught and wrapped.
471      * Then it prints the wrapped exception and continues with stack frames
472      * until the wrapper exception is caught and wrapped again, etc.</p>
473      *
474      * <p>The output of this method is consistent across JDK versions.
475      * Note that this is the opposite order to the JDK1.4 display.</p>
476      *
477      * <p>The method is equivalent to <code>printStackTrace</code> for throwables
478      * that don't have nested causes.</p>
479      *
480      * @param throwable  the throwable to output, may be null
481      * @param writer  the writer to output to, may not be null
482      * @throws IllegalArgumentException if the writer is <code>null</code>
483      * @since 2.0
484      */
485     public static void printRootCauseStackTrace(final Throwable throwable, final PrintWriter writer) {
486         if (throwable == null) {
487             return;
488         }
489         Validate.isTrue(writer != null, "The PrintWriter must not be null");
490         final String trace[] = getRootCauseStackTrace(throwable);
491         for (final String element : trace) {
492             writer.println(element);
493         }
494         writer.flush();
495     }
496 
497     //-----------------------------------------------------------------------
498     /**
499      * <p>Creates a compact stack trace for the root cause of the supplied
500      * <code>Throwable</code>.</p>
501      *
502      * <p>The output of this method is consistent across JDK versions.
503      * It consists of the root exception followed by each of its wrapping
504      * exceptions separated by '[wrapped]'. Note that this is the opposite
505      * order to the JDK1.4 display.</p>
506      *
507      * @param throwable  the throwable to examine, may be null
508      * @return an array of stack trace frames, never null
509      * @since 2.0
510      */
511     public static String[] getRootCauseStackTrace(final Throwable throwable) {
512         if (throwable == null) {
513             return ArrayUtils.EMPTY_STRING_ARRAY;
514         }
515         final Throwable throwables[] = getThrowables(throwable);
516         final int count = throwables.length;
517         final List<String> frames = new ArrayList<>();
518         List<String> nextTrace = getStackFrameList(throwables[count - 1]);
519         for (int i = count; --i >= 0;) {
520             final List<String> trace = nextTrace;
521             if (i != 0) {
522                 nextTrace = getStackFrameList(throwables[i - 1]);
523                 removeCommonFrames(trace, nextTrace);
524             }
525             if (i == count - 1) {
526                 frames.add(throwables[i].toString());
527             } else {
528                 frames.add(WRAPPED_MARKER + throwables[i].toString());
529             }
530             for (int j = 0; j < trace.size(); j++) {
531                 frames.add(trace.get(j));
532             }
533         }
534         return frames.toArray(new String[frames.size()]);
535     }
536 
537     /**
538      * <p>Removes common frames from the cause trace given the two stack traces.</p>
539      *
540      * @param causeFrames  stack trace of a cause throwable
541      * @param wrapperFrames  stack trace of a wrapper throwable
542      * @throws IllegalArgumentException if either argument is null
543      * @since 2.0
544      */
545     public static void removeCommonFrames(final List<String> causeFrames, final List<String> wrapperFrames) {
546         if (causeFrames == null || wrapperFrames == null) {
547             throw new IllegalArgumentException("The List must not be null");
548         }
549         int causeFrameIndex = causeFrames.size() - 1;
550         int wrapperFrameIndex = wrapperFrames.size() - 1;
551         while (causeFrameIndex >= 0 && wrapperFrameIndex >= 0) {
552             // Remove the frame from the cause trace if it is the same
553             // as in the wrapper trace
554             final String causeFrame = causeFrames.get(causeFrameIndex);
555             final String wrapperFrame = wrapperFrames.get(wrapperFrameIndex);
556             if (causeFrame.equals(wrapperFrame)) {
557                 causeFrames.remove(causeFrameIndex);
558             }
559             causeFrameIndex--;
560             wrapperFrameIndex--;
561         }
562     }
563 
564     //-----------------------------------------------------------------------
565     /**
566      * <p>Gets the stack trace from a Throwable as a String.</p>
567      *
568      * <p>The result of this method vary by JDK version as this method
569      * uses {@link Throwable#printStackTrace(java.io.PrintWriter)}.
570      * On JDK1.3 and earlier, the cause exception will not be shown
571      * unless the specified throwable alters printStackTrace.</p>
572      *
573      * @param throwable  the <code>Throwable</code> to be examined
574      * @return the stack trace as generated by the exception's
575      *  <code>printStackTrace(PrintWriter)</code> method
576      */
577     public static String getStackTrace(final Throwable throwable) {
578         final StringWriter sw = new StringWriter();
579         final PrintWriter pw = new PrintWriter(sw, true);
580         throwable.printStackTrace(pw);
581         return sw.getBuffer().toString();
582     }
583 
584     /**
585      * <p>Captures the stack trace associated with the specified
586      * <code>Throwable</code> object, decomposing it into a list of
587      * stack frames.</p>
588      *
589      * <p>The result of this method vary by JDK version as this method
590      * uses {@link Throwable#printStackTrace(java.io.PrintWriter)}.
591      * On JDK1.3 and earlier, the cause exception will not be shown
592      * unless the specified throwable alters printStackTrace.</p>
593      *
594      * @param throwable  the <code>Throwable</code> to examine, may be null
595      * @return an array of strings describing each stack frame, never null
596      */
597     public static String[] getStackFrames(final Throwable throwable) {
598         if (throwable == null) {
599             return ArrayUtils.EMPTY_STRING_ARRAY;
600         }
601         return getStackFrames(getStackTrace(throwable));
602     }
603 
604     //-----------------------------------------------------------------------
605     /**
606      * <p>Returns an array where each element is a line from the argument.</p>
607      *
608      * <p>The end of line is determined by the value of {@link SystemUtils#LINE_SEPARATOR}.</p>
609      *
610      * @param stackTrace  a stack trace String
611      * @return an array where each element is a line from the argument
612      */
613     static String[] getStackFrames(final String stackTrace) {
614         final String linebreak = System.lineSeparator();
615         final StringTokenizer frames = new StringTokenizer(stackTrace, linebreak);
616         final List<String> list = new ArrayList<>();
617         while (frames.hasMoreTokens()) {
618             list.add(frames.nextToken());
619         }
620         return list.toArray(new String[list.size()]);
621     }
622 
623     /**
624      * <p>Produces a <code>List</code> of stack frames - the message
625      * is not included. Only the trace of the specified exception is
626      * returned, any caused by trace is stripped.</p>
627      *
628      * <p>This works in most cases - it will only fail if the exception
629      * message contains a line that starts with:
630      * <code>&quot;&nbsp;&nbsp;&nbsp;at&quot;.</code></p>
631      *
632      * @param t is any throwable
633      * @return List of stack frames
634      */
635     static List<String> getStackFrameList(final Throwable t) {
636         final String stackTrace = getStackTrace(t);
637         final String linebreak = System.lineSeparator();
638         final StringTokenizer frames = new StringTokenizer(stackTrace, linebreak);
639         final List<String> list = new ArrayList<>();
640         boolean traceStarted = false;
641         while (frames.hasMoreTokens()) {
642             final String token = frames.nextToken();
643             // Determine if the line starts with <whitespace>at
644             final int at = token.indexOf("at");
645             if (at != -1 && token.substring(0, at).trim().isEmpty()) {
646                 traceStarted = true;
647                 list.add(token);
648             } else if (traceStarted) {
649                 break;
650             }
651         }
652         return list;
653     }
654 
655     //-----------------------------------------------------------------------
656     /**
657      * Gets a short message summarising the exception.
658      * <p>
659      * The message returned is of the form
660      * {ClassNameWithoutPackage}: {ThrowableMessage}
661      *
662      * @param th  the throwable to get a message for, null returns empty string
663      * @return the message, non-null
664      * @since Commons Lang 2.2
665      */
666     public static String getMessage(final Throwable th) {
667         if (th == null) {
668             return StringUtils.EMPTY;
669         }
670         final String clsName = ClassUtils.getShortClassName(th, null);
671         final String msg = th.getMessage();
672         return clsName + ": " + StringUtils.defaultString(msg);
673     }
674 
675     //-----------------------------------------------------------------------
676     /**
677      * Gets a short message summarising the root cause exception.
678      * <p>
679      * The message returned is of the form
680      * {ClassNameWithoutPackage}: {ThrowableMessage}
681      *
682      * @param th  the throwable to get a message for, null returns empty string
683      * @return the message, non-null
684      * @since Commons Lang 2.2
685      */
686     public static String getRootCauseMessage(final Throwable th) {
687         Throwable root = ExceptionUtils.getRootCause(th);
688         root = root == null ? th : root;
689         return getMessage(root);
690     }
691 
692     /**
693      * Throw a checked exception without adding the exception to the throws
694      * clause of the calling method. This method prevents throws clause
695      * pollution and reduces the clutter of "Caused by" exceptions in the
696      * stacktrace.
697      * <p>
698      * The use of this technique may be controversial, but exceedingly useful to
699      * library developers.
700      * <code>
701      *  public int propagateExample { // note that there is no throws clause
702      *      try {
703      *          return invocation(); // throws IOException
704      *      } catch (Exception e) {
705      *          return ExceptionUtils.rethrow(e);  // propagates a checked exception
706      *      }
707      *  }
708      * </code>
709      * <p>
710      * This is an alternative to the more conservative approach of wrapping the
711      * checked exception in a RuntimeException:
712      * <code>
713      *  public int wrapExample { // note that there is no throws clause
714      *      try {
715      *          return invocation(); // throws IOException
716      *      } catch (Error e) {
717      *          throw e;
718      *      } catch (RuntimeException e) {
719      *          throw e;  // wraps a checked exception
720      *      } catch (Exception e) {
721      *          throw new UndeclaredThrowableException(e);  // wraps a checked exception
722      *      }
723      *  }
724      * </code>
725      * <p>
726      * One downside to using this approach is that the java compiler will not
727      * allow invoking code to specify a checked exception in a catch clause
728      * unless there is some code path within the try block that has invoked a
729      * method declared with that checked exception. If the invoking site wishes
730      * to catch the shaded checked exception, it must either invoke the shaded
731      * code through a method re-declaring the desired checked exception, or
732      * catch Exception and use the instanceof operator. Either of these
733      * techniques are required when interacting with non-java jvm code such as
734      * Jython, Scala, or Groovy, since these languages do not consider any
735      * exceptions as checked.
736      *
737      * @param throwable
738      *            The throwable to rethrow.
739      * @param <R> The type of the returned value.
740      * @return Never actually returned, this generic type matches any type
741      *         which the calling site requires. "Returning" the results of this
742      *         method, as done in the propagateExample above, will satisfy the
743      *         java compiler requirement that all code paths return a value.
744      * @since 3.5
745      * @see #wrapAndThrow(Throwable)
746      */
747     public static <R> R rethrow(final Throwable throwable) {
748         // claim that the typeErasure invocation throws a RuntimeException
749         return ExceptionUtils.<R, RuntimeException> typeErasure(throwable);
750     }
751 
752     /**
753      * Claim a Throwable is another Exception type using type erasure. This
754      * hides a checked exception from the java compiler, allowing a checked
755      * exception to be thrown without having the exception in the method's throw
756      * clause.
757      */
758     @SuppressWarnings("unchecked")
759     private static <R, T extends Throwable> R typeErasure(final Throwable throwable) throws T {
760         throw (T) throwable;
761     }
762 
763     /**
764      * Throw a checked exception without adding the exception to the throws
765      * clause of the calling method. For checked exceptions, this method throws
766      * an UndeclaredThrowableException wrapping the checked exception. For
767      * Errors and RuntimeExceptions, the original exception is rethrown.
768      * <p>
769      * The downside to using this approach is that invoking code which needs to
770      * handle specific checked exceptions must sniff up the exception chain to
771      * determine if the caught exception was caused by the checked exception.
772      *
773      * @param throwable
774      *            The throwable to rethrow.
775      * @param <R> The type of the returned value.
776      * @return Never actually returned, this generic type matches any type
777      *         which the calling site requires. "Returning" the results of this
778      *         method will satisfy the java compiler requirement that all code
779      *         paths return a value.
780      * @since 3.5
781      * @see #rethrow(Throwable)
782      * @see #hasCause(Throwable, Class)
783      */
784     public static <R> R wrapAndThrow(final Throwable throwable) {
785         if (throwable instanceof RuntimeException) {
786             throw (RuntimeException) throwable;
787         }
788         if (throwable instanceof Error) {
789             throw (Error) throwable;
790         }
791         throw new UndeclaredThrowableException(throwable);
792     }
793 
794     /**
795      * Does the throwable's causal chain have an immediate or wrapped exception
796      * of the given type?
797      *
798      * @param chain
799      *            The root of a Throwable causal chain.
800      * @param type
801      *            The exception type to test.
802      * @return true, if chain is an instance of type or is an
803      *         UndeclaredThrowableException wrapping a cause.
804      * @since 3.5
805      * @see #wrapAndThrow(Throwable)
806      */
807     public static boolean hasCause(Throwable chain,
808             final Class<? extends Throwable> type) {
809         if (chain instanceof UndeclaredThrowableException) {
810             chain = chain.getCause();
811         }
812         return type.isInstance(chain);
813     }
814 }