Java tutorial
/* * Copyright @ 2006-2010 by The Jxva Framework Foundation * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. * */ package com.jxva.exception; import java.io.PrintStream; import java.io.PrintWriter; import java.io.StringWriter; import java.lang.reflect.Field; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.sql.SQLException; import java.util.ArrayList; import java.util.Arrays; import java.util.List; import java.util.StringTokenizer; import com.jxva.util.ArrayUtil; import com.jxva.util.StringUtil; import com.jxva.util.SystemUtil; /** * <p>Provides utilities for manipulating and examining * <code>Throwable</code> objects.</p> * @author The Jxva Framework * @since 1.0 * @version 2008-11-27 13:38:58 by Jxva */ public class ExceptionUtil { /** * <p>Used when printing stack frames to denote the start of a * wrapped exception.</p> * * <p>Package private for accessibility by test suite.</p> */ public static final String WRAPPED_MARKER = " [wrapped] "; private static String[] CAUSE_METHOD_NAMES = { "getCause", "getNextException", "getTargetException", "getException", "getSourceException", "getRootCause", "getCausedByException", "getNested", "getLinkedException", "getNestedException", "getLinkedCause", "getThrowable", }; /** * <p>The Method object for Java 1.4 getCause.</p> */ private static final Method THROWABLE_CAUSE_METHOD; /** * <p>The Method object for Java 1.4 initCause.</p> */ private static final Method THROWABLE_INITCAUSE_METHOD; static { Method causeMethod; try { causeMethod = Throwable.class.getMethod("getCause"); } catch (Exception e) { causeMethod = null; } THROWABLE_CAUSE_METHOD = causeMethod; try { causeMethod = Throwable.class.getMethod("initCause", new Class[] { Throwable.class }); } catch (Exception e) { causeMethod = null; } THROWABLE_INITCAUSE_METHOD = causeMethod; } /** * <p> * Public constructor allows an instance of <code>ExceptionUtils</code> to be created, although that is not * normally necessary. * </p> */ public ExceptionUtil() { super(); } //----------------------------------------------------------------------- /** * <p>Adds to the list of method names used in the search for <code>Throwable</code> * objects.</p> * * @param methodName the methodName to add to the list, <code>null</code> * and empty strings are ignored * @since 2.0 */ public static void addCauseMethodName(String methodName) { if (!StringUtil.isEmpty(methodName) && !isCauseMethodName(methodName)) { List<String> list = getCauseMethodNameList(); if (list.add(methodName)) { synchronized (CAUSE_METHOD_NAMES) { CAUSE_METHOD_NAMES = toArray(list); } } } } /** * <p>Removes from the list of method names used in the search for <code>Throwable</code> * objects.</p> * * @param methodName the methodName to remove from the list, <code>null</code> * and empty strings are ignored * @since 2.1 */ public static void removeCauseMethodName(String methodName) { if (!StringUtil.isEmpty(methodName)) { List<String> list = getCauseMethodNameList(); if (list.remove(methodName)) { synchronized (CAUSE_METHOD_NAMES) { CAUSE_METHOD_NAMES = toArray(list); } } } } /** * <p>Sets the cause of a <code>Throwable</code> using introspection, allowing * source code compatibility between pre-1.4 and post-1.4 Java releases.</p> * * <p>The typical use of this method is inside a constructor as in * the following example:</p> * * <pre> * import org.apache.commons.lang.exception.ExceptionUtils; * * public class MyException extends Exception { * * public MyException(String msg) { * super(msg); * } * * public MyException(String msg, Throwable cause) { * super(msg); * ExceptionUtils.setCause(this, cause); * } * } * </pre> * * @param target the target <code>Throwable</code> * @param cause the <code>Throwable</code> to set in the target * @return a <code>true</code> if the target has been modified * @since 2.2 */ public static boolean setCause(Throwable target, Throwable cause) { if (target == null) { throw new ArgumentException("target"); } Object[] causeArgs = new Object[] { cause }; boolean modifiedTarget = false; if (THROWABLE_INITCAUSE_METHOD != null) { try { THROWABLE_INITCAUSE_METHOD.invoke(target, causeArgs); modifiedTarget = true; } catch (IllegalAccessException ignored) { // Exception ignored. } catch (InvocationTargetException ignored) { // Exception ignored. } } try { Method setCauseMethod = target.getClass().getMethod("setCause", new Class[] { Throwable.class }); setCauseMethod.invoke(target, causeArgs); modifiedTarget = true; } catch (NoSuchMethodException ignored) { // Exception ignored. } catch (IllegalAccessException ignored) { // Exception ignored. } catch (InvocationTargetException ignored) { // Exception ignored. } return modifiedTarget; } private static String[] toArray(List<String> list) { return list.toArray(new String[list.size()]); } private static ArrayList<String> getCauseMethodNameList() { synchronized (CAUSE_METHOD_NAMES) { return new ArrayList<String>(Arrays.asList(CAUSE_METHOD_NAMES)); } } public static boolean isCauseMethodName(String methodName) { synchronized (CAUSE_METHOD_NAMES) { return ArrayUtil.indexOf(CAUSE_METHOD_NAMES, methodName) >= 0; } } //----------------------------------------------------------------------- /** * <p>Introspects the <code>Throwable</code> to obtain the cause.</p> * * <p>The method searches for methods with specific names that return a * <code>Throwable</code> object. This will pick up most wrapping exceptions, * including those from JDK 1.4, and * {@link org.apache.commons.lang.exception.NestableException NestableException}. * The method names can be added to using {@link #addCauseMethodName(String)}.</p> * * <p>The default list searched for are:</p> * <ul> * <li><code>getCause()</code></li> * <li><code>getNextException()</code></li> * <li><code>getTargetException()</code></li> * <li><code>getException()</code></li> * <li><code>getSourceException()</code></li> * <li><code>getRootCause()</code></li> * <li><code>getCausedByException()</code></li> * <li><code>getNested()</code></li> * </ul> * * <p>In the absence of any such method, the object is inspected for a * <code>detail</code> field assignable to a <code>Throwable</code>.</p> * * <p>If none of the above is found, returns <code>null</code>.</p> * * @param throwable the throwable to introspect for a cause, may be null * @return the cause of the <code>Throwable</code>, * <code>null</code> if none found or null throwable input * @since 1.0 */ public static Throwable getCause(Throwable throwable) { synchronized (CAUSE_METHOD_NAMES) { return getCause(throwable, CAUSE_METHOD_NAMES); } } /** * <p>Introspects the <code>Throwable</code> to obtain the cause.</p> * * <ol> * <li>Try known exception types.</li> * <li>Try the supplied array of method names.</li> * <li>Try the field 'detail'.</li> * </ol> * * <p>A <code>null</code> set of method names means use the default set. * A <code>null</code> in the set of method names will be ignored.</p> * * @param throwable the throwable to introspect for a cause, may be null * @param methodNames the method names, null treated as default set * @return the cause of the <code>Throwable</code>, * <code>null</code> if none found or null throwable input * @since 1.0 */ public static Throwable getCause(Throwable throwable, String[] methodNames) { if (throwable == null) { return null; } Throwable cause = getCauseUsingWellKnownTypes(throwable); if (cause == null) { if (methodNames == null) { synchronized (CAUSE_METHOD_NAMES) { methodNames = CAUSE_METHOD_NAMES; } } for (int i = 0; i < methodNames.length; i++) { String methodName = methodNames[i]; if (methodName != null) { cause = getCauseUsingMethodName(throwable, methodName); if (cause != null) { break; } } } if (cause == null) { cause = getCauseUsingFieldName(throwable, "detail"); } } return cause; } /** * <p>Introspects the <code>Throwable</code> to obtain the root cause.</p> * * <p>This method walks through the exception chain to the last element, * "root" of the tree, using {@link #getCause(Throwable)}, and * returns that exception.</p> * * <p>From version 2.2, this method handles recursive cause structures * that might otherwise cause infinite loops. If the throwable parameter * has a cause of itself, then null will be returned. If the throwable * parameter cause chain loops, the last element in the chain before the * loop is returned.</p> * * @param throwable the throwable to get the root cause for, may be null * @return the root cause of the <code>Throwable</code>, * <code>null</code> if none found or null throwable input */ public static Throwable getRootCause(Throwable throwable) { List<Throwable> list = getThrowableList(throwable); return (list.size() < 2 ? null : list.get(list.size() - 1)); } /** * <p>Finds a <code>Throwable</code> for known types.</p> * * <p>Uses <code>instanceof</code> checks to examine the exception, * looking for well known types which could contain chained or * wrapped exceptions.</p> * * @param throwable the exception to examine * @return the wrapped exception, or <code>null</code> if not found */ private static Throwable getCauseUsingWellKnownTypes(Throwable throwable) { if (throwable instanceof Nestable) { return ((Nestable) throwable).getCause(); } else if (throwable instanceof SQLException) { return ((SQLException) throwable).getNextException(); } else if (throwable instanceof InvocationTargetException) { return ((InvocationTargetException) throwable).getTargetException(); } else { return null; } } /** * <p>Finds a <code>Throwable</code> by method name.</p> * * @param throwable the exception to examine * @param methodName the name of the method to find and invoke * @return the wrapped exception, or <code>null</code> if not found */ private static Throwable getCauseUsingMethodName(Throwable throwable, String methodName) { Method method = null; try { method = throwable.getClass().getMethod(methodName); } catch (NoSuchMethodException ignored) { // exception ignored } catch (SecurityException ignored) { // exception ignored } if (method != null && Throwable.class.isAssignableFrom(method.getReturnType())) { try { return (Throwable) method.invoke(throwable, ArrayUtil.EMPTY_OBJECT_ARRAY); } catch (IllegalAccessException ignored) { // exception ignored } catch (IllegalArgumentException ignored) { // exception ignored } catch (InvocationTargetException ignored) { // exception ignored } } return null; } /** * <p>Finds a <code>Throwable</code> by field name.</p> * * @param throwable the exception to examine * @param fieldName the name of the attribute to examine * @return the wrapped exception, or <code>null</code> if not found */ private static Throwable getCauseUsingFieldName(Throwable throwable, String fieldName) { Field field = null; try { field = throwable.getClass().getField(fieldName); } catch (NoSuchFieldException ignored) { // exception ignored } catch (SecurityException ignored) { // exception ignored } if (field != null && Throwable.class.isAssignableFrom(field.getType())) { try { return (Throwable) field.get(throwable); } catch (IllegalAccessException ignored) { // exception ignored } catch (IllegalArgumentException ignored) { // exception ignored } } return null; } //----------------------------------------------------------------------- /** * <p>Checks if the Throwable class has a <code>getCause</code> method.</p> * * <p>This is true for JDK 1.4 and above.</p> * * @return true if Throwable is nestable * @since 2.0 */ public static boolean isThrowableNested() { return THROWABLE_CAUSE_METHOD != null; } /** * <p>Checks whether this <code>Throwable</code> class can store a cause.</p> * * <p>This method does <b>not</b> check whether it actually does store a cause.<p> * * @param throwable the <code>Throwable</code> to examine, may be null * @return boolean <code>true</code> if nested otherwise <code>false</code> * @since 2.0 */ public static boolean isNestedThrowable(Throwable throwable) { if (throwable == null) { return false; } if (throwable instanceof Nestable) { return true; } else if (throwable instanceof SQLException) { return true; } else if (throwable instanceof InvocationTargetException) { return true; } else if (isThrowableNested()) { return true; } Class<? extends Throwable> cls = throwable.getClass(); synchronized (CAUSE_METHOD_NAMES) { for (int i = 0, isize = CAUSE_METHOD_NAMES.length; i < isize; i++) { try { Method method = cls.getMethod(CAUSE_METHOD_NAMES[i]); if (method != null && Throwable.class.isAssignableFrom(method.getReturnType())) { return true; } } catch (NoSuchMethodException ignored) { // exception ignored } catch (SecurityException ignored) { // exception ignored } } } try { Field field = cls.getField("detail"); if (field != null) { return true; } } catch (NoSuchFieldException ignored) { // exception ignored } catch (SecurityException ignored) { // exception ignored } return false; } /** * <p>Counts the number of <code>Throwable</code> objects in the * exception chain.</p> * * <p>A throwable without cause will return <code>1</code>. * A throwable with one cause will return <code>2</code> and so on. * A <code>null</code> throwable will return <code>0</code>.</p> * * <p>From version 2.2, this method handles recursive cause structures * that might otherwise cause infinite loops. The cause chain is * processed until the end is reached, or until the next item in the * chain is already in the result set.</p> * * @param throwable the throwable to inspect, may be null * @return the count of throwables, zero if null input */ public static int getThrowableCount(Throwable throwable) { return getThrowableList(throwable).size(); } /** * <p>Returns the list of <code>Throwable</code> objects in the * exception chain.</p> * * <p>A throwable without cause will return an array containing * one element - the input throwable. * A throwable with one cause will return an array containing * two elements. - the input throwable and the cause throwable. * A <code>null</code> throwable will return an array of size zero.</p> * * <p>From version 2.2, this method handles recursive cause structures * that might otherwise cause infinite loops. The cause chain is * processed until the end is reached, or until the next item in the * chain is already in the result set.</p> * * @see #getThrowableList(Throwable) * @param throwable the throwable to inspect, may be null * @return the array of throwables, never null */ public static Throwable[] getThrowables(Throwable throwable) { List<Throwable> list = getThrowableList(throwable); return list.toArray(new Throwable[list.size()]); } /** * <p>Returns the list of <code>Throwable</code> objects in the * exception chain.</p> * * <p>A throwable without cause will return a list containing * one element - the input throwable. * A throwable with one cause will return a list containing * two elements. - the input throwable and the cause throwable. * A <code>null</code> throwable will return a list of size zero.</p> * * <p>This method handles recursive cause structures that might * otherwise cause infinite loops. The cause chain is processed until * the end is reached, or until the next item in the chain is already * in the result set.</p> * * @param throwable the throwable to inspect, may be null * @return the list of throwables, never null * @since Commons Lang 2.2 */ public static List<Throwable> getThrowableList(Throwable throwable) { List<Throwable> list = new ArrayList<Throwable>(); while (throwable != null && list.contains(throwable) == false) { list.add(throwable); throwable = getCause(throwable); } return list; } //----------------------------------------------------------------------- /** * <p>Returns the (zero based) index of the first <code>Throwable</code> * that matches the specified class (exactly) in the exception chain. * Subclasses of the specified class do not match - see * {@link #indexOfType(Throwable, Class)} for the opposite.</p> * * <p>A <code>null</code> throwable returns <code>-1</code>. * A <code>null</code> type returns <code>-1</code>. * No match in the chain returns <code>-1</code>.</p> * * @param throwable the throwable to inspect, may be null * @param clazz the class to search for, subclasses do not match, null returns -1 * @return the index into the throwable chain, -1 if no match or null input */ public static int indexOfThrowable(Throwable throwable, Class<?> clazz) { return indexOf(throwable, clazz, 0, false); } /** * <p>Returns the (zero based) index of the first <code>Throwable</code> * that matches the specified type in the exception chain from * a specified index. * Subclasses of the specified class do not match - see * {@link #indexOfType(Throwable, Class, int)} for the opposite.</p> * * <p>A <code>null</code> throwable returns <code>-1</code>. * A <code>null</code> type returns <code>-1</code>. * No match in the chain returns <code>-1</code>. * A negative start index is treated as zero. * A start index greater than the number of throwables returns <code>-1</code>.</p> * * @param throwable the throwable to inspect, may be null * @param clazz the class to search for, subclasses do not match, null returns -1 * @param fromIndex the (zero based) index of the starting position, * negative treated as zero, larger than chain size returns -1 * @return the index into the throwable chain, -1 if no match or null input */ public static int indexOfThrowable(Throwable throwable, Class<?> clazz, int fromIndex) { return indexOf(throwable, clazz, fromIndex, false); } //----------------------------------------------------------------------- /** * <p>Returns the (zero based) index of the first <code>Throwable</code> * that matches the specified class or subclass in the exception chain. * Subclasses of the specified class do match - see * {@link #indexOfThrowable(Throwable, Class)} for the opposite.</p> * * <p>A <code>null</code> throwable returns <code>-1</code>. * A <code>null</code> type returns <code>-1</code>. * No match in the chain returns <code>-1</code>.</p> * * @param throwable the throwable to inspect, may be null * @param type the type to search for, subclasses match, null returns -1 * @return the index into the throwable chain, -1 if no match or null input * @since 2.1 */ public static int indexOfType(Throwable throwable, Class<?> type) { return indexOf(throwable, type, 0, true); } /** * <p>Returns the (zero based) index of the first <code>Throwable</code> * that matches the specified type in the exception chain from * a specified index. * Subclasses of the specified class do match - see * {@link #indexOfThrowable(Throwable, Class)} for the opposite.</p> * * <p>A <code>null</code> throwable returns <code>-1</code>. * A <code>null</code> type returns <code>-1</code>. * No match in the chain returns <code>-1</code>. * A negative start index is treated as zero. * A start index greater than the number of throwables returns <code>-1</code>.</p> * * @param throwable the throwable to inspect, may be null * @param type the type to search for, subclasses match, null returns -1 * @param fromIndex the (zero based) index of the starting position, * negative treated as zero, larger than chain size returns -1 * @return the index into the throwable chain, -1 if no match or null input * @since 2.1 */ public static int indexOfType(Throwable throwable, Class<?> type, int fromIndex) { return indexOf(throwable, type, fromIndex, true); } /** * <p>Worker method for the <code>indexOfType</code> methods.</p> * * @param throwable the throwable to inspect, may be null * @param type the type to search for, subclasses match, null returns -1 * @param fromIndex the (zero based) index of the starting position, * negative treated as zero, larger than chain size returns -1 * @param subclass if <code>true</code>, compares with {@link Class#isAssignableFrom(Class)}, otherwise compares * using references * @return index of the <code>type</code> within throwables nested withing the specified <code>throwable</code> */ private static int indexOf(Throwable throwable, Class<?> type, int fromIndex, boolean subclass) { if (throwable == null || type == null) { return -1; } if (fromIndex < 0) { fromIndex = 0; } Throwable[] throwables = getThrowables(throwable); if (fromIndex >= throwables.length) { return -1; } if (subclass) { for (int i = fromIndex; i < throwables.length; i++) { if (type.isAssignableFrom(throwables[i].getClass())) { return i; } } } else { for (int i = fromIndex; i < throwables.length; i++) { if (type.equals(throwables[i].getClass())) { return i; } } } return -1; } /** * <p>Prints a compact stack trace for the root cause of a throwable * to <code>System.err</code>.</p> * * <p>The compact stack trace starts with the root cause and prints * stack frames up to the place where it was caught and wrapped. * Then it prints the wrapped exception and continues with stack frames * until the wrapper exception is caught and wrapped again, etc.</p> * * <p>The output of this method is consistent across JDK versions. * Note that this is the opposite order to the JDK1.4 display.</p> * * <p>The method is equivalent to <code>printStackTrace</code> for throwables * that don't have nested causes.</p> * * @param throwable the throwable to output * @since 2.0 */ public static void printRootCauseStackTrace(Throwable throwable) { printRootCauseStackTrace(throwable, System.err); } /** * <p>Prints a compact stack trace for the root cause of a throwable.</p> * * <p>The compact stack trace starts with the root cause and prints * stack frames up to the place where it was caught and wrapped. * Then it prints the wrapped exception and continues with stack frames * until the wrapper exception is caught and wrapped again, etc.</p> * * <p>The output of this method is consistent across JDK versions. * Note that this is the opposite order to the JDK1.4 display.</p> * * <p>The method is equivalent to <code>printStackTrace</code> for throwables * that don't have nested causes.</p> * * @param throwable the throwable to output, may be null * @param stream the stream to output to, may not be null * @throws IllegalArgumentException if the stream is <code>null</code> * @since 2.0 */ public static void printRootCauseStackTrace(Throwable throwable, PrintStream stream) { if (throwable == null) { return; } if (stream == null) { throw new IllegalArgumentException("The PrintStream must not be null"); } String trace[] = getRootCauseStackTrace(throwable); for (int i = 0; i < trace.length; i++) { stream.println(trace[i]); } stream.flush(); } /** * <p>Prints a compact stack trace for the root cause of a throwable.</p> * * <p>The compact stack trace starts with the root cause and prints * stack frames up to the place where it was caught and wrapped. * Then it prints the wrapped exception and continues with stack frames * until the wrapper exception is caught and wrapped again, etc.</p> * * <p>The output of this method is consistent across JDK versions. * Note that this is the opposite order to the JDK1.4 display.</p> * * <p>The method is equivalent to <code>printStackTrace</code> for throwables * that don't have nested causes.</p> * * @param throwable the throwable to output, may be null * @param writer the writer to output to, may not be null * @throws IllegalArgumentException if the writer is <code>null</code> * @since 2.0 */ public static void printRootCauseStackTrace(Throwable throwable, PrintWriter writer) { if (throwable == null) { return; } if (writer == null) { throw new IllegalArgumentException("The PrintWriter must not be null"); } String trace[] = getRootCauseStackTrace(throwable); for (int i = 0; i < trace.length; i++) { writer.println(trace[i]); } writer.flush(); } //----------------------------------------------------------------------- /** * <p>Creates a compact stack trace for the root cause of the supplied * <code>Throwable</code>.</p> * * <p>The output of this method is consistent across JDK versions. * It consists of the root exception followed by each of its wrapping * exceptions separated by '[wrapped]'. Note that this is the opposite * order to the JDK1.4 display.</p> * * @param throwable the throwable to examine, may be null * @return an array of stack trace frames, never null * @since 2.0 */ public static String[] getRootCauseStackTrace(Throwable throwable) { if (throwable == null) { return ArrayUtil.EMPTY_STRING_ARRAY; } Throwable throwables[] = getThrowables(throwable); int count = throwables.length; ArrayList<String> frames = new ArrayList<String>(); List<String> nextTrace = getStackFrameList(throwables[count - 1]); for (int i = count; --i >= 0;) { List<String> trace = nextTrace; if (i != 0) { nextTrace = getStackFrameList(throwables[i - 1]); removeCommonFrames(trace, nextTrace); } if (i == count - 1) { frames.add(throwables[i].toString()); } else { frames.add(WRAPPED_MARKER + throwables[i].toString()); } for (int j = 0; j < trace.size(); j++) { frames.add(trace.get(j)); } } return frames.toArray(new String[0]); } /** * <p>Removes common frames from the cause trace given the two stack traces.</p> * * @param causeFrames stack trace of a cause throwable * @param wrapperFrames stack trace of a wrapper throwable * @throws IllegalArgumentException if either argument is null * @since 2.0 */ public static void removeCommonFrames(List<String> causeFrames, List<String> wrapperFrames) { if (causeFrames == null || wrapperFrames == null) { throw new IllegalArgumentException("The List must not be null"); } int causeFrameIndex = causeFrames.size() - 1; int wrapperFrameIndex = wrapperFrames.size() - 1; while (causeFrameIndex >= 0 && wrapperFrameIndex >= 0) { // Remove the frame from the cause trace if it is the same // as in the wrapper trace String causeFrame = causeFrames.get(causeFrameIndex); String wrapperFrame = wrapperFrames.get(wrapperFrameIndex); if (causeFrame.equals(wrapperFrame)) { causeFrames.remove(causeFrameIndex); } causeFrameIndex--; wrapperFrameIndex--; } } //----------------------------------------------------------------------- /** * <p>A way to get the entire nested stack-trace of an throwable.</p> * * <p>The result of this method is highly dependent on the JDK version * and whether the exceptions override printStackTrace or not.</p> * * @param throwable the <code>Throwable</code> to be examined * @return the nested stack trace, with the root cause first * @since 2.0 */ public static String getFullStackTrace(Throwable throwable) { StringWriter sw = new StringWriter(); PrintWriter pw = new PrintWriter(sw, true); Throwable[] ts = getThrowables(throwable); for (int i = 0; i < ts.length; i++) { ts[i].printStackTrace(pw); if (isNestedThrowable(ts[i])) { break; } } return sw.getBuffer().toString(); } //----------------------------------------------------------------------- /** * <p>Gets the stack trace from a Throwable as a String.</p> * * <p>The result of this method vary by JDK version as this method * uses {@link Throwable#printStackTrace(java.io.PrintWriter)}. * On JDK1.3 and earlier, the cause exception will not be shown * unless the specified throwable alters printStackTrace.</p> * * @param throwable the <code>Throwable</code> to be examined * @return the stack trace as generated by the exception's * <code>printStackTrace(PrintWriter)</code> method */ public static String getStackTrace(Throwable throwable) { StringWriter sw = new StringWriter(); PrintWriter pw = new PrintWriter(sw, true); throwable.printStackTrace(pw); return sw.getBuffer().toString(); } /** * <p>Captures the stack trace associated with the specified * <code>Throwable</code> object, decomposing it into a list of * stack frames.</p> * * <p>The result of this method vary by JDK version as this method * uses {@link Throwable#printStackTrace(java.io.PrintWriter)}. * On JDK1.3 and earlier, the cause exception will not be shown * unless the specified throwable alters printStackTrace.</p> * * @param throwable the <code>Throwable</code> to examine, may be null * @return an array of strings describing each stack frame, never null */ public static String[] getStackFrames(Throwable throwable) { if (throwable == null) { return ArrayUtil.EMPTY_STRING_ARRAY; } return getStackFrames(getStackTrace(throwable)); } //----------------------------------------------------------------------- /** * <p>Returns an array where each element is a line from the argument.</p> * * <p>The end of line is determined by the value of {@link SystemUtils#LINE_SEPARATOR}.</p> * * <p>Functionality shared between the * <code>getStackFrames(Throwable)</code> methods of this and the * {@link org.apache.commons.lang.exception.NestableDelegate} classes.</p> * * @param stackTrace a stack trace String * @return an array where each element is a line from the argument */ static String[] getStackFrames(String stackTrace) { String linebreak = SystemUtil.LINE_SEPARATOR; StringTokenizer frames = new StringTokenizer(stackTrace, linebreak); List<String> list = new ArrayList<String>(); while (frames.hasMoreTokens()) { list.add(frames.nextToken()); } return toArray(list); } /** * <p>Produces a <code>List</code> of stack frames - the message * is not included. Only the trace of the specified exception is * returned, any caused by trace is stripped.</p> * * <p>This works in most cases - it will only fail if the exception * message contains a line that starts with: * <code>" at".</code></p> * * @param t is any throwable * @return List of stack frames */ static List<String> getStackFrameList(Throwable t) { String stackTrace = getStackTrace(t); String linebreak = SystemUtil.LINE_SEPARATOR; StringTokenizer frames = new StringTokenizer(stackTrace, linebreak); List<String> list = new ArrayList<String>(); boolean traceStarted = false; while (frames.hasMoreTokens()) { String token = frames.nextToken(); // Determine if the line starts with <whitespace>at int at = token.indexOf("at"); if (at != -1 && token.substring(0, at).trim().length() == 0) { traceStarted = true; list.add(token); } else if (traceStarted) { break; } } return list; } //----------------------------------------------------------------------- /** * Gets a short message summarising the exception. * <p> * The message returned is of the form * {ClassNameWithoutPackage}: {ThrowableMessage} * * @param th the throwable to get a message for, null returns empty string * @return the message, non-null * @since Commons Lang 2.2 */ public static String getMessage(Throwable th) { if (th == null) { return ""; } String clsName = th.getClass().getName(); String msg = th.getMessage(); return clsName + ": " + (msg == null ? "" : msg); } //----------------------------------------------------------------------- /** * Gets a short message summarising the root cause exception. * <p> * The message returned is of the form * {ClassNameWithoutPackage}: {ThrowableMessage} * * @param th the throwable to get a message for, null returns empty string * @return the message, non-null * @since Commons Lang 2.2 */ public static String getRootCauseMessage(Throwable th) { Throwable root = getRootCause(th); root = (root == null ? th : root); return getMessage(root); } }