001 /* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 package org.apache.commons.lang.exception; 018 019 import java.io.PrintStream; 020 import java.io.PrintWriter; 021 import java.io.StringWriter; 022 import java.lang.reflect.Field; 023 import java.lang.reflect.InvocationTargetException; 024 import java.lang.reflect.Method; 025 import java.sql.SQLException; 026 import java.util.ArrayList; 027 import java.util.Arrays; 028 import java.util.List; 029 import java.util.StringTokenizer; 030 031 import org.apache.commons.lang.ArrayUtils; 032 import org.apache.commons.lang.ClassUtils; 033 import org.apache.commons.lang.NullArgumentException; 034 import org.apache.commons.lang.StringUtils; 035 import org.apache.commons.lang.SystemUtils; 036 037 /** 038 * <p>Provides utilities for manipulating and examining 039 * <code>Throwable</code> objects.</p> 040 * 041 * @author Daniel L. Rall 042 * @author Dmitri Plotnikov 043 * @author Stephen Colebourne 044 * @author <a href="mailto:ggregory@seagullsw.com">Gary Gregory</a> 045 * @author Pete Gieser 046 * @since 1.0 047 * @version $Id: ExceptionUtils.java 594278 2007-11-12 19:58:30Z bayard $ 048 */ 049 public class ExceptionUtils { 050 051 /** 052 * <p>Used when printing stack frames to denote the start of a 053 * wrapped exception.</p> 054 * 055 * <p>Package private for accessibility by test suite.</p> 056 */ 057 static final String WRAPPED_MARKER = " [wrapped] "; 058 059 /** 060 * <p>The names of methods commonly used to access a wrapped exception.</p> 061 */ 062 private static String[] CAUSE_METHOD_NAMES = { 063 "getCause", 064 "getNextException", 065 "getTargetException", 066 "getException", 067 "getSourceException", 068 "getRootCause", 069 "getCausedByException", 070 "getNested", 071 "getLinkedException", 072 "getNestedException", 073 "getLinkedCause", 074 "getThrowable", 075 }; 076 077 /** 078 * <p>The Method object for Java 1.4 getCause.</p> 079 */ 080 private static final Method THROWABLE_CAUSE_METHOD; 081 082 /** 083 * <p>The Method object for Java 1.4 initCause.</p> 084 */ 085 private static final Method THROWABLE_INITCAUSE_METHOD; 086 087 static { 088 Method causeMethod; 089 try { 090 causeMethod = Throwable.class.getMethod("getCause", null); 091 } catch (Exception e) { 092 causeMethod = null; 093 } 094 THROWABLE_CAUSE_METHOD = causeMethod; 095 try { 096 causeMethod = Throwable.class.getMethod("initCause", new Class[]{Throwable.class}); 097 } catch (Exception e) { 098 causeMethod = null; 099 } 100 THROWABLE_INITCAUSE_METHOD = causeMethod; 101 } 102 103 /** 104 * <p> 105 * Public constructor allows an instance of <code>ExceptionUtils</code> to be created, although that is not 106 * normally necessary. 107 * </p> 108 */ 109 public ExceptionUtils() { 110 super(); 111 } 112 113 //----------------------------------------------------------------------- 114 /** 115 * <p>Adds to the list of method names used in the search for <code>Throwable</code> 116 * objects.</p> 117 * 118 * @param methodName the methodName to add to the list, <code>null</code> 119 * and empty strings are ignored 120 * @since 2.0 121 */ 122 public static void addCauseMethodName(String methodName) { 123 if (StringUtils.isNotEmpty(methodName) && !isCauseMethodName(methodName)) { 124 List list = getCauseMethodNameList(); 125 if (list.add(methodName)) { 126 synchronized(CAUSE_METHOD_NAMES) { 127 CAUSE_METHOD_NAMES = toArray(list); 128 } 129 } 130 } 131 } 132 133 /** 134 * <p>Removes from the list of method names used in the search for <code>Throwable</code> 135 * objects.</p> 136 * 137 * @param methodName the methodName to remove from the list, <code>null</code> 138 * and empty strings are ignored 139 * @since 2.1 140 */ 141 public static void removeCauseMethodName(String methodName) { 142 if (StringUtils.isNotEmpty(methodName)) { 143 List list = getCauseMethodNameList(); 144 if (list.remove(methodName)) { 145 synchronized(CAUSE_METHOD_NAMES) { 146 CAUSE_METHOD_NAMES = toArray(list); 147 } 148 } 149 } 150 } 151 152 /** 153 * <p>Sets the cause of a <code>Throwable</code> using introspection, allowing 154 * source code compatibility between pre-1.4 and post-1.4 Java releases.</p> 155 * 156 * <p>The typical use of this method is inside a constructor as in 157 * the following example:</p> 158 * 159 * <pre> 160 * import org.apache.commons.lang.exception.ExceptionUtils; 161 * 162 * public class MyException extends Exception { 163 * 164 * public MyException(String msg) { 165 * super(msg); 166 * } 167 * 168 * public MyException(String msg, Throwable cause) { 169 * super(msg); 170 * ExceptionUtils.setCause(this, cause); 171 * } 172 * } 173 * </pre> 174 * 175 * @param target the target <code>Throwable</code> 176 * @param cause the <code>Throwable</code> to set in the target 177 * @return a <code>true</code> if the target has been modified 178 * @since 2.2 179 */ 180 public static boolean setCause(Throwable target, Throwable cause) { 181 if (target == null) { 182 throw new NullArgumentException("target"); 183 } 184 Object[] causeArgs = new Object[]{cause}; 185 boolean modifiedTarget = false; 186 if (THROWABLE_INITCAUSE_METHOD != null) { 187 try { 188 THROWABLE_INITCAUSE_METHOD.invoke(target, causeArgs); 189 modifiedTarget = true; 190 } catch (IllegalAccessException ignored) { 191 // Exception ignored. 192 } catch (InvocationTargetException ignored) { 193 // Exception ignored. 194 } 195 } 196 try { 197 Method setCauseMethod = target.getClass().getMethod("setCause", new Class[]{Throwable.class}); 198 setCauseMethod.invoke(target, causeArgs); 199 modifiedTarget = true; 200 } catch (NoSuchMethodException ignored) { 201 // Exception ignored. 202 } catch (IllegalAccessException ignored) { 203 // Exception ignored. 204 } catch (InvocationTargetException ignored) { 205 // Exception ignored. 206 } 207 return modifiedTarget; 208 } 209 210 /** 211 * Returns the given list as a <code>String[]</code>. 212 * @param list a list to transform. 213 * @return the given list as a <code>String[]</code>. 214 */ 215 private static String[] toArray(List list) { 216 return (String[]) list.toArray(new String[list.size()]); 217 } 218 219 /** 220 * Returns {@link #CAUSE_METHOD_NAMES} as a List. 221 * 222 * @return {@link #CAUSE_METHOD_NAMES} as a List. 223 */ 224 private static ArrayList getCauseMethodNameList() { 225 synchronized(CAUSE_METHOD_NAMES) { 226 return new ArrayList(Arrays.asList(CAUSE_METHOD_NAMES)); 227 } 228 } 229 230 /** 231 * <p>Tests if the list of method names used in the search for <code>Throwable</code> 232 * objects include the given name.</p> 233 * 234 * @param methodName the methodName to search in the list. 235 * @return if the list of method names used in the search for <code>Throwable</code> 236 * objects include the given name. 237 * @since 2.1 238 */ 239 public static boolean isCauseMethodName(String methodName) { 240 synchronized(CAUSE_METHOD_NAMES) { 241 return ArrayUtils.indexOf(CAUSE_METHOD_NAMES, methodName) >= 0; 242 } 243 } 244 245 //----------------------------------------------------------------------- 246 /** 247 * <p>Introspects the <code>Throwable</code> to obtain the cause.</p> 248 * 249 * <p>The method searches for methods with specific names that return a 250 * <code>Throwable</code> object. This will pick up most wrapping exceptions, 251 * including those from JDK 1.4, and 252 * {@link org.apache.commons.lang.exception.NestableException NestableException}. 253 * The method names can be added to using {@link #addCauseMethodName(String)}.</p> 254 * 255 * <p>The default list searched for are:</p> 256 * <ul> 257 * <li><code>getCause()</code></li> 258 * <li><code>getNextException()</code></li> 259 * <li><code>getTargetException()</code></li> 260 * <li><code>getException()</code></li> 261 * <li><code>getSourceException()</code></li> 262 * <li><code>getRootCause()</code></li> 263 * <li><code>getCausedByException()</code></li> 264 * <li><code>getNested()</code></li> 265 * </ul> 266 * 267 * <p>In the absence of any such method, the object is inspected for a 268 * <code>detail</code> field assignable to a <code>Throwable</code>.</p> 269 * 270 * <p>If none of the above is found, returns <code>null</code>.</p> 271 * 272 * @param throwable the throwable to introspect for a cause, may be null 273 * @return the cause of the <code>Throwable</code>, 274 * <code>null</code> if none found or null throwable input 275 * @since 1.0 276 */ 277 public static Throwable getCause(Throwable throwable) { 278 synchronized(CAUSE_METHOD_NAMES) { 279 return getCause(throwable, CAUSE_METHOD_NAMES); 280 } 281 } 282 283 /** 284 * <p>Introspects the <code>Throwable</code> to obtain the cause.</p> 285 * 286 * <ol> 287 * <li>Try known exception types.</li> 288 * <li>Try the supplied array of method names.</li> 289 * <li>Try the field 'detail'.</li> 290 * </ol> 291 * 292 * <p>A <code>null</code> set of method names means use the default set. 293 * A <code>null</code> in the set of method names will be ignored.</p> 294 * 295 * @param throwable the throwable to introspect for a cause, may be null 296 * @param methodNames the method names, null treated as default set 297 * @return the cause of the <code>Throwable</code>, 298 * <code>null</code> if none found or null throwable input 299 * @since 1.0 300 */ 301 public static Throwable getCause(Throwable throwable, String[] methodNames) { 302 if (throwable == null) { 303 return null; 304 } 305 Throwable cause = getCauseUsingWellKnownTypes(throwable); 306 if (cause == null) { 307 if (methodNames == null) { 308 synchronized(CAUSE_METHOD_NAMES) { 309 methodNames = CAUSE_METHOD_NAMES; 310 } 311 } 312 for (int i = 0; i < methodNames.length; i++) { 313 String methodName = methodNames[i]; 314 if (methodName != null) { 315 cause = getCauseUsingMethodName(throwable, methodName); 316 if (cause != null) { 317 break; 318 } 319 } 320 } 321 322 if (cause == null) { 323 cause = getCauseUsingFieldName(throwable, "detail"); 324 } 325 } 326 return cause; 327 } 328 329 /** 330 * <p>Introspects the <code>Throwable</code> to obtain the root cause.</p> 331 * 332 * <p>This method walks through the exception chain to the last element, 333 * "root" of the tree, using {@link #getCause(Throwable)}, and 334 * returns that exception.</p> 335 * 336 * <p>From version 2.2, this method handles recursive cause structures 337 * that might otherwise cause infinite loops. If the throwable parameter 338 * has a cause of itself, then null will be returned. If the throwable 339 * parameter cause chain loops, the last element in the chain before the 340 * loop is returned.</p> 341 * 342 * @param throwable the throwable to get the root cause for, may be null 343 * @return the root cause of the <code>Throwable</code>, 344 * <code>null</code> if none found or null throwable input 345 */ 346 public static Throwable getRootCause(Throwable throwable) { 347 List list = getThrowableList(throwable); 348 return (list.size() < 2 ? null : (Throwable)list.get(list.size() - 1)); 349 } 350 351 /** 352 * <p>Finds a <code>Throwable</code> for known types.</p> 353 * 354 * <p>Uses <code>instanceof</code> checks to examine the exception, 355 * looking for well known types which could contain chained or 356 * wrapped exceptions.</p> 357 * 358 * @param throwable the exception to examine 359 * @return the wrapped exception, or <code>null</code> if not found 360 */ 361 private static Throwable getCauseUsingWellKnownTypes(Throwable throwable) { 362 if (throwable instanceof Nestable) { 363 return ((Nestable) throwable).getCause(); 364 } else if (throwable instanceof SQLException) { 365 return ((SQLException) throwable).getNextException(); 366 } else if (throwable instanceof InvocationTargetException) { 367 return ((InvocationTargetException) throwable).getTargetException(); 368 } else { 369 return null; 370 } 371 } 372 373 /** 374 * <p>Finds a <code>Throwable</code> by method name.</p> 375 * 376 * @param throwable the exception to examine 377 * @param methodName the name of the method to find and invoke 378 * @return the wrapped exception, or <code>null</code> if not found 379 */ 380 private static Throwable getCauseUsingMethodName(Throwable throwable, String methodName) { 381 Method method = null; 382 try { 383 method = throwable.getClass().getMethod(methodName, null); 384 } catch (NoSuchMethodException ignored) { 385 // exception ignored 386 } catch (SecurityException ignored) { 387 // exception ignored 388 } 389 390 if (method != null && Throwable.class.isAssignableFrom(method.getReturnType())) { 391 try { 392 return (Throwable) method.invoke(throwable, ArrayUtils.EMPTY_OBJECT_ARRAY); 393 } catch (IllegalAccessException ignored) { 394 // exception ignored 395 } catch (IllegalArgumentException ignored) { 396 // exception ignored 397 } catch (InvocationTargetException ignored) { 398 // exception ignored 399 } 400 } 401 return null; 402 } 403 404 /** 405 * <p>Finds a <code>Throwable</code> by field name.</p> 406 * 407 * @param throwable the exception to examine 408 * @param fieldName the name of the attribute to examine 409 * @return the wrapped exception, or <code>null</code> if not found 410 */ 411 private static Throwable getCauseUsingFieldName(Throwable throwable, String fieldName) { 412 Field field = null; 413 try { 414 field = throwable.getClass().getField(fieldName); 415 } catch (NoSuchFieldException ignored) { 416 // exception ignored 417 } catch (SecurityException ignored) { 418 // exception ignored 419 } 420 421 if (field != null && Throwable.class.isAssignableFrom(field.getType())) { 422 try { 423 return (Throwable) field.get(throwable); 424 } catch (IllegalAccessException ignored) { 425 // exception ignored 426 } catch (IllegalArgumentException ignored) { 427 // exception ignored 428 } 429 } 430 return null; 431 } 432 433 //----------------------------------------------------------------------- 434 /** 435 * <p>Checks if the Throwable class has a <code>getCause</code> method.</p> 436 * 437 * <p>This is true for JDK 1.4 and above.</p> 438 * 439 * @return true if Throwable is nestable 440 * @since 2.0 441 */ 442 public static boolean isThrowableNested() { 443 return THROWABLE_CAUSE_METHOD != null; 444 } 445 446 /** 447 * <p>Checks whether this <code>Throwable</code> class can store a cause.</p> 448 * 449 * <p>This method does <b>not</b> check whether it actually does store a cause.<p> 450 * 451 * @param throwable the <code>Throwable</code> to examine, may be null 452 * @return boolean <code>true</code> if nested otherwise <code>false</code> 453 * @since 2.0 454 */ 455 public static boolean isNestedThrowable(Throwable throwable) { 456 if (throwable == null) { 457 return false; 458 } 459 460 if (throwable instanceof Nestable) { 461 return true; 462 } else if (throwable instanceof SQLException) { 463 return true; 464 } else if (throwable instanceof InvocationTargetException) { 465 return true; 466 } else if (isThrowableNested()) { 467 return true; 468 } 469 470 Class cls = throwable.getClass(); 471 synchronized(CAUSE_METHOD_NAMES) { 472 for (int i = 0, isize = CAUSE_METHOD_NAMES.length; i < isize; i++) { 473 try { 474 Method method = cls.getMethod(CAUSE_METHOD_NAMES[i], null); 475 if (method != null && Throwable.class.isAssignableFrom(method.getReturnType())) { 476 return true; 477 } 478 } catch (NoSuchMethodException ignored) { 479 // exception ignored 480 } catch (SecurityException ignored) { 481 // exception ignored 482 } 483 } 484 } 485 486 try { 487 Field field = cls.getField("detail"); 488 if (field != null) { 489 return true; 490 } 491 } catch (NoSuchFieldException ignored) { 492 // exception ignored 493 } catch (SecurityException ignored) { 494 // exception ignored 495 } 496 497 return false; 498 } 499 500 //----------------------------------------------------------------------- 501 /** 502 * <p>Counts the number of <code>Throwable</code> objects in the 503 * exception chain.</p> 504 * 505 * <p>A throwable without cause will return <code>1</code>. 506 * A throwable with one cause will return <code>2</code> and so on. 507 * A <code>null</code> throwable will return <code>0</code>.</p> 508 * 509 * <p>From version 2.2, this method handles recursive cause structures 510 * that might otherwise cause infinite loops. The cause chain is 511 * processed until the end is reached, or until the next item in the 512 * chain is already in the result set.</p> 513 * 514 * @param throwable the throwable to inspect, may be null 515 * @return the count of throwables, zero if null input 516 */ 517 public static int getThrowableCount(Throwable throwable) { 518 return getThrowableList(throwable).size(); 519 } 520 521 /** 522 * <p>Returns the list of <code>Throwable</code> objects in the 523 * exception chain.</p> 524 * 525 * <p>A throwable without cause will return an array containing 526 * one element - the input throwable. 527 * A throwable with one cause will return an array containing 528 * two elements. - the input throwable and the cause throwable. 529 * A <code>null</code> throwable will return an array of size zero.</p> 530 * 531 * <p>From version 2.2, this method handles recursive cause structures 532 * that might otherwise cause infinite loops. The cause chain is 533 * processed until the end is reached, or until the next item in the 534 * chain is already in the result set.</p> 535 * 536 * @see #getThrowableList(Throwable) 537 * @param throwable the throwable to inspect, may be null 538 * @return the array of throwables, never null 539 */ 540 public static Throwable[] getThrowables(Throwable throwable) { 541 List list = getThrowableList(throwable); 542 return (Throwable[]) list.toArray(new Throwable[list.size()]); 543 } 544 545 /** 546 * <p>Returns the list of <code>Throwable</code> objects in the 547 * exception chain.</p> 548 * 549 * <p>A throwable without cause will return a list containing 550 * one element - the input throwable. 551 * A throwable with one cause will return a list containing 552 * two elements. - the input throwable and the cause throwable. 553 * A <code>null</code> throwable will return a list of size zero.</p> 554 * 555 * <p>This method handles recursive cause structures that might 556 * otherwise cause infinite loops. The cause chain is processed until 557 * the end is reached, or until the next item in the chain is already 558 * in the result set.</p> 559 * 560 * @param throwable the throwable to inspect, may be null 561 * @return the list of throwables, never null 562 * @since Commons Lang 2.2 563 */ 564 public static List getThrowableList(Throwable throwable) { 565 List list = new ArrayList(); 566 while (throwable != null && list.contains(throwable) == false) { 567 list.add(throwable); 568 throwable = ExceptionUtils.getCause(throwable); 569 } 570 return list; 571 } 572 573 //----------------------------------------------------------------------- 574 /** 575 * <p>Returns the (zero based) index of the first <code>Throwable</code> 576 * that matches the specified class (exactly) in the exception chain. 577 * Subclasses of the specified class do not match - see 578 * {@link #indexOfType(Throwable, Class)} for the opposite.</p> 579 * 580 * <p>A <code>null</code> throwable returns <code>-1</code>. 581 * A <code>null</code> type returns <code>-1</code>. 582 * No match in the chain returns <code>-1</code>.</p> 583 * 584 * @param throwable the throwable to inspect, may be null 585 * @param clazz the class to search for, subclasses do not match, null returns -1 586 * @return the index into the throwable chain, -1 if no match or null input 587 */ 588 public static int indexOfThrowable(Throwable throwable, Class clazz) { 589 return indexOf(throwable, clazz, 0, false); 590 } 591 592 /** 593 * <p>Returns the (zero based) index of the first <code>Throwable</code> 594 * that matches the specified type in the exception chain from 595 * a specified index. 596 * Subclasses of the specified class do not match - see 597 * {@link #indexOfType(Throwable, Class, int)} for the opposite.</p> 598 * 599 * <p>A <code>null</code> throwable returns <code>-1</code>. 600 * A <code>null</code> type returns <code>-1</code>. 601 * No match in the chain returns <code>-1</code>. 602 * A negative start index is treated as zero. 603 * A start index greater than the number of throwables returns <code>-1</code>.</p> 604 * 605 * @param throwable the throwable to inspect, may be null 606 * @param clazz the class to search for, subclasses do not match, null returns -1 607 * @param fromIndex the (zero based) index of the starting position, 608 * negative treated as zero, larger than chain size returns -1 609 * @return the index into the throwable chain, -1 if no match or null input 610 */ 611 public static int indexOfThrowable(Throwable throwable, Class clazz, int fromIndex) { 612 return indexOf(throwable, clazz, fromIndex, false); 613 } 614 615 //----------------------------------------------------------------------- 616 /** 617 * <p>Returns the (zero based) index of the first <code>Throwable</code> 618 * that matches the specified class or subclass in the exception chain. 619 * Subclasses of the specified class do match - see 620 * {@link #indexOfThrowable(Throwable, Class)} for the opposite.</p> 621 * 622 * <p>A <code>null</code> throwable returns <code>-1</code>. 623 * A <code>null</code> type returns <code>-1</code>. 624 * No match in the chain returns <code>-1</code>.</p> 625 * 626 * @param throwable the throwable to inspect, may be null 627 * @param type the type to search for, subclasses match, null returns -1 628 * @return the index into the throwable chain, -1 if no match or null input 629 * @since 2.1 630 */ 631 public static int indexOfType(Throwable throwable, Class type) { 632 return indexOf(throwable, type, 0, true); 633 } 634 635 /** 636 * <p>Returns the (zero based) index of the first <code>Throwable</code> 637 * that matches the specified type in the exception chain from 638 * a specified index. 639 * Subclasses of the specified class do match - see 640 * {@link #indexOfThrowable(Throwable, Class)} for the opposite.</p> 641 * 642 * <p>A <code>null</code> throwable returns <code>-1</code>. 643 * A <code>null</code> type returns <code>-1</code>. 644 * No match in the chain returns <code>-1</code>. 645 * A negative start index is treated as zero. 646 * A start index greater than the number of throwables returns <code>-1</code>.</p> 647 * 648 * @param throwable the throwable to inspect, may be null 649 * @param type the type to search for, subclasses match, null returns -1 650 * @param fromIndex the (zero based) index of the starting position, 651 * negative treated as zero, larger than chain size returns -1 652 * @return the index into the throwable chain, -1 if no match or null input 653 * @since 2.1 654 */ 655 public static int indexOfType(Throwable throwable, Class type, int fromIndex) { 656 return indexOf(throwable, type, fromIndex, true); 657 } 658 659 /** 660 * <p>Worker method for the <code>indexOfType</code> methods.</p> 661 * 662 * @param throwable the throwable to inspect, may be null 663 * @param type the type to search for, subclasses match, null returns -1 664 * @param fromIndex the (zero based) index of the starting position, 665 * negative treated as zero, larger than chain size returns -1 666 * @param subclass if <code>true</code>, compares with {@link Class#isAssignableFrom(Class)}, otherwise compares 667 * using references 668 * @return index of the <code>type</code> within throwables nested withing the specified <code>throwable</code> 669 */ 670 private static int indexOf(Throwable throwable, Class type, int fromIndex, boolean subclass) { 671 if (throwable == null || type == null) { 672 return -1; 673 } 674 if (fromIndex < 0) { 675 fromIndex = 0; 676 } 677 Throwable[] throwables = ExceptionUtils.getThrowables(throwable); 678 if (fromIndex >= throwables.length) { 679 return -1; 680 } 681 if (subclass) { 682 for (int i = fromIndex; i < throwables.length; i++) { 683 if (type.isAssignableFrom(throwables[i].getClass())) { 684 return i; 685 } 686 } 687 } else { 688 for (int i = fromIndex; i < throwables.length; i++) { 689 if (type.equals(throwables[i].getClass())) { 690 return i; 691 } 692 } 693 } 694 return -1; 695 } 696 697 //----------------------------------------------------------------------- 698 /** 699 * <p>Prints a compact stack trace for the root cause of a throwable 700 * to <code>System.err</code>.</p> 701 * 702 * <p>The compact stack trace starts with the root cause and prints 703 * stack frames up to the place where it was caught and wrapped. 704 * Then it prints the wrapped exception and continues with stack frames 705 * until the wrapper exception is caught and wrapped again, etc.</p> 706 * 707 * <p>The output of this method is consistent across JDK versions. 708 * Note that this is the opposite order to the JDK1.4 display.</p> 709 * 710 * <p>The method is equivalent to <code>printStackTrace</code> for throwables 711 * that don't have nested causes.</p> 712 * 713 * @param throwable the throwable to output 714 * @since 2.0 715 */ 716 public static void printRootCauseStackTrace(Throwable throwable) { 717 printRootCauseStackTrace(throwable, System.err); 718 } 719 720 /** 721 * <p>Prints a compact stack trace for the root cause of a throwable.</p> 722 * 723 * <p>The compact stack trace starts with the root cause and prints 724 * stack frames up to the place where it was caught and wrapped. 725 * Then it prints the wrapped exception and continues with stack frames 726 * until the wrapper exception is caught and wrapped again, etc.</p> 727 * 728 * <p>The output of this method is consistent across JDK versions. 729 * Note that this is the opposite order to the JDK1.4 display.</p> 730 * 731 * <p>The method is equivalent to <code>printStackTrace</code> for throwables 732 * that don't have nested causes.</p> 733 * 734 * @param throwable the throwable to output, may be null 735 * @param stream the stream to output to, may not be null 736 * @throws IllegalArgumentException if the stream is <code>null</code> 737 * @since 2.0 738 */ 739 public static void printRootCauseStackTrace(Throwable throwable, PrintStream stream) { 740 if (throwable == null) { 741 return; 742 } 743 if (stream == null) { 744 throw new IllegalArgumentException("The PrintStream must not be null"); 745 } 746 String trace[] = getRootCauseStackTrace(throwable); 747 for (int i = 0; i < trace.length; i++) { 748 stream.println(trace[i]); 749 } 750 stream.flush(); 751 } 752 753 /** 754 * <p>Prints a compact stack trace for the root cause of a throwable.</p> 755 * 756 * <p>The compact stack trace starts with the root cause and prints 757 * stack frames up to the place where it was caught and wrapped. 758 * Then it prints the wrapped exception and continues with stack frames 759 * until the wrapper exception is caught and wrapped again, etc.</p> 760 * 761 * <p>The output of this method is consistent across JDK versions. 762 * Note that this is the opposite order to the JDK1.4 display.</p> 763 * 764 * <p>The method is equivalent to <code>printStackTrace</code> for throwables 765 * that don't have nested causes.</p> 766 * 767 * @param throwable the throwable to output, may be null 768 * @param writer the writer to output to, may not be null 769 * @throws IllegalArgumentException if the writer is <code>null</code> 770 * @since 2.0 771 */ 772 public static void printRootCauseStackTrace(Throwable throwable, PrintWriter writer) { 773 if (throwable == null) { 774 return; 775 } 776 if (writer == null) { 777 throw new IllegalArgumentException("The PrintWriter must not be null"); 778 } 779 String trace[] = getRootCauseStackTrace(throwable); 780 for (int i = 0; i < trace.length; i++) { 781 writer.println(trace[i]); 782 } 783 writer.flush(); 784 } 785 786 //----------------------------------------------------------------------- 787 /** 788 * <p>Creates a compact stack trace for the root cause of the supplied 789 * <code>Throwable</code>.</p> 790 * 791 * <p>The output of this method is consistent across JDK versions. 792 * It consists of the root exception followed by each of its wrapping 793 * exceptions separated by '[wrapped]'. Note that this is the opposite 794 * order to the JDK1.4 display.</p> 795 * 796 * @param throwable the throwable to examine, may be null 797 * @return an array of stack trace frames, never null 798 * @since 2.0 799 */ 800 public static String[] getRootCauseStackTrace(Throwable throwable) { 801 if (throwable == null) { 802 return ArrayUtils.EMPTY_STRING_ARRAY; 803 } 804 Throwable throwables[] = getThrowables(throwable); 805 int count = throwables.length; 806 ArrayList frames = new ArrayList(); 807 List nextTrace = getStackFrameList(throwables[count - 1]); 808 for (int i = count; --i >= 0;) { 809 List trace = nextTrace; 810 if (i != 0) { 811 nextTrace = getStackFrameList(throwables[i - 1]); 812 removeCommonFrames(trace, nextTrace); 813 } 814 if (i == count - 1) { 815 frames.add(throwables[i].toString()); 816 } else { 817 frames.add(WRAPPED_MARKER + throwables[i].toString()); 818 } 819 for (int j = 0; j < trace.size(); j++) { 820 frames.add(trace.get(j)); 821 } 822 } 823 return (String[]) frames.toArray(new String[0]); 824 } 825 826 /** 827 * <p>Removes common frames from the cause trace given the two stack traces.</p> 828 * 829 * @param causeFrames stack trace of a cause throwable 830 * @param wrapperFrames stack trace of a wrapper throwable 831 * @throws IllegalArgumentException if either argument is null 832 * @since 2.0 833 */ 834 public static void removeCommonFrames(List causeFrames, List wrapperFrames) { 835 if (causeFrames == null || wrapperFrames == null) { 836 throw new IllegalArgumentException("The List must not be null"); 837 } 838 int causeFrameIndex = causeFrames.size() - 1; 839 int wrapperFrameIndex = wrapperFrames.size() - 1; 840 while (causeFrameIndex >= 0 && wrapperFrameIndex >= 0) { 841 // Remove the frame from the cause trace if it is the same 842 // as in the wrapper trace 843 String causeFrame = (String) causeFrames.get(causeFrameIndex); 844 String wrapperFrame = (String) wrapperFrames.get(wrapperFrameIndex); 845 if (causeFrame.equals(wrapperFrame)) { 846 causeFrames.remove(causeFrameIndex); 847 } 848 causeFrameIndex--; 849 wrapperFrameIndex--; 850 } 851 } 852 853 //----------------------------------------------------------------------- 854 /** 855 * <p>A way to get the entire nested stack-trace of an throwable.</p> 856 * 857 * <p>The result of this method is highly dependent on the JDK version 858 * and whether the exceptions override printStackTrace or not.</p> 859 * 860 * @param throwable the <code>Throwable</code> to be examined 861 * @return the nested stack trace, with the root cause first 862 * @since 2.0 863 */ 864 public static String getFullStackTrace(Throwable throwable) { 865 StringWriter sw = new StringWriter(); 866 PrintWriter pw = new PrintWriter(sw, true); 867 Throwable[] ts = getThrowables(throwable); 868 for (int i = 0; i < ts.length; i++) { 869 ts[i].printStackTrace(pw); 870 if (isNestedThrowable(ts[i])) { 871 break; 872 } 873 } 874 return sw.getBuffer().toString(); 875 } 876 877 //----------------------------------------------------------------------- 878 /** 879 * <p>Gets the stack trace from a Throwable as a String.</p> 880 * 881 * <p>The result of this method vary by JDK version as this method 882 * uses {@link Throwable#printStackTrace(java.io.PrintWriter)}. 883 * On JDK1.3 and earlier, the cause exception will not be shown 884 * unless the specified throwable alters printStackTrace.</p> 885 * 886 * @param throwable the <code>Throwable</code> to be examined 887 * @return the stack trace as generated by the exception's 888 * <code>printStackTrace(PrintWriter)</code> method 889 */ 890 public static String getStackTrace(Throwable throwable) { 891 StringWriter sw = new StringWriter(); 892 PrintWriter pw = new PrintWriter(sw, true); 893 throwable.printStackTrace(pw); 894 return sw.getBuffer().toString(); 895 } 896 897 /** 898 * <p>Captures the stack trace associated with the specified 899 * <code>Throwable</code> object, decomposing it into a list of 900 * stack frames.</p> 901 * 902 * <p>The result of this method vary by JDK version as this method 903 * uses {@link Throwable#printStackTrace(java.io.PrintWriter)}. 904 * On JDK1.3 and earlier, the cause exception will not be shown 905 * unless the specified throwable alters printStackTrace.</p> 906 * 907 * @param throwable the <code>Throwable</code> to examine, may be null 908 * @return an array of strings describing each stack frame, never null 909 */ 910 public static String[] getStackFrames(Throwable throwable) { 911 if (throwable == null) { 912 return ArrayUtils.EMPTY_STRING_ARRAY; 913 } 914 return getStackFrames(getStackTrace(throwable)); 915 } 916 917 //----------------------------------------------------------------------- 918 /** 919 * <p>Returns an array where each element is a line from the argument.</p> 920 * 921 * <p>The end of line is determined by the value of {@link SystemUtils#LINE_SEPARATOR}.</p> 922 * 923 * <p>Functionality shared between the 924 * <code>getStackFrames(Throwable)</code> methods of this and the 925 * {@link org.apache.commons.lang.exception.NestableDelegate} classes.</p> 926 * 927 * @param stackTrace a stack trace String 928 * @return an array where each element is a line from the argument 929 */ 930 static String[] getStackFrames(String stackTrace) { 931 String linebreak = SystemUtils.LINE_SEPARATOR; 932 StringTokenizer frames = new StringTokenizer(stackTrace, linebreak); 933 List list = new ArrayList(); 934 while (frames.hasMoreTokens()) { 935 list.add(frames.nextToken()); 936 } 937 return toArray(list); 938 } 939 940 /** 941 * <p>Produces a <code>List</code> of stack frames - the message 942 * is not included. Only the trace of the specified exception is 943 * returned, any caused by trace is stripped.</p> 944 * 945 * <p>This works in most cases - it will only fail if the exception 946 * message contains a line that starts with: 947 * <code>" at".</code></p> 948 * 949 * @param t is any throwable 950 * @return List of stack frames 951 */ 952 static List getStackFrameList(Throwable t) { 953 String stackTrace = getStackTrace(t); 954 String linebreak = SystemUtils.LINE_SEPARATOR; 955 StringTokenizer frames = new StringTokenizer(stackTrace, linebreak); 956 List list = new ArrayList(); 957 boolean traceStarted = false; 958 while (frames.hasMoreTokens()) { 959 String token = frames.nextToken(); 960 // Determine if the line starts with <whitespace>at 961 int at = token.indexOf("at"); 962 if (at != -1 && token.substring(0, at).trim().length() == 0) { 963 traceStarted = true; 964 list.add(token); 965 } else if (traceStarted) { 966 break; 967 } 968 } 969 return list; 970 } 971 972 //----------------------------------------------------------------------- 973 /** 974 * Gets a short message summarising the exception. 975 * <p> 976 * The message returned is of the form 977 * {ClassNameWithoutPackage}: {ThrowableMessage} 978 * 979 * @param th the throwable to get a message for, null returns empty string 980 * @return the message, non-null 981 * @since Commons Lang 2.2 982 */ 983 public static String getMessage(Throwable th) { 984 if (th == null) { 985 return ""; 986 } 987 String clsName = ClassUtils.getShortClassName(th, null); 988 String msg = th.getMessage(); 989 return clsName + ": " + StringUtils.defaultString(msg); 990 } 991 992 //----------------------------------------------------------------------- 993 /** 994 * Gets a short message summarising the root cause exception. 995 * <p> 996 * The message returned is of the form 997 * {ClassNameWithoutPackage}: {ThrowableMessage} 998 * 999 * @param th the throwable to get a message for, null returns empty string 1000 * @return the message, non-null 1001 * @since Commons Lang 2.2 1002 */ 1003 public static String getRootCauseMessage(Throwable th) { 1004 Throwable root = ExceptionUtils.getRootCause(th); 1005 root = (root == null ? th : root); 1006 return getMessage(root); 1007 } 1008 1009 }