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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.commons.lang3.exception;

import java.io.PrintStream;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;
import java.util.StringTokenizer;

import org.apache.commons.lang3.ArrayUtils;
import org.apache.commons.lang3.ClassUtils;
import org.apache.commons.lang3.StringUtils;
import org.apache.commons.lang3.SystemUtils;

/**
 * 

Provides utilities for manipulating and examining * Throwable objects.

* * @since 1.0 * @version $Id: ExceptionUtils.java 1436770 2013-01-22 07:09:45Z ggregory $ */ public class ExceptionUtils { /** *

Used when printing stack frames to denote the start of a * wrapped exception.

* *

Package private for accessibility by test suite.

*/ static final String WRAPPED_MARKER = " [wrapped] "; /** *

The names of methods commonly used to access a wrapped exception.

*/ // TODO: Remove in Lang 4.0 private static final String[] CAUSE_METHOD_NAMES = { "getCause", "getNextException", "getTargetException", "getException", "getSourceException", "getRootCause", "getCausedByException", "getNested", "getLinkedException", "getNestedException", "getLinkedCause", "getThrowable", }; /** *

* Public constructor allows an instance of ExceptionUtils to be created, although that is not * normally necessary. *

*/ public ExceptionUtils() { super(); } //----------------------------------------------------------------------- /** *

Returns the default names used when searching for the cause of an exception.

* *

This may be modified and used in the overloaded getCause(Throwable, String[]) method.

* * @return cloned array of the default method names * @since 3.0 * @deprecated This feature will be removed in Lang 4.0 */ @Deprecated public static String[] getDefaultCauseMethodNames() { return ArrayUtils.clone(CAUSE_METHOD_NAMES); } //----------------------------------------------------------------------- /** *

Introspects the Throwable to obtain the cause.

* *

The method searches for methods with specific names that return a * Throwable object. This will pick up most wrapping exceptions, * including those from JDK 1.4. * *

The default list searched for are:

*
    *
  • getCause()
  • *
  • getNextException()
  • *
  • getTargetException()
  • *
  • getException()
  • *
  • getSourceException()
  • *
  • getRootCause()
  • *
  • getCausedByException()
  • *
  • getNested()
  • *
* *

If none of the above is found, returns null.

* * @param throwable the throwable to introspect for a cause, may be null * @return the cause of the Throwable, * null if none found or null throwable input * @since 1.0 * @deprecated This feature will be removed in Lang 4.0 */ @Deprecated public static Throwable getCause(final Throwable throwable) { return getCause(throwable, CAUSE_METHOD_NAMES); } /** *

Introspects the Throwable to obtain the cause.

* *

A null set of method names means use the default set. * A null in the set of method names will be ignored.

* * @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 Throwable, * null if none found or null throwable input * @since 1.0 * @deprecated This feature will be removed in Lang 4.0 */ @Deprecated public static Throwable getCause(final Throwable throwable, String[] methodNames) { if (throwable == null) { return null; } if (methodNames == null) { methodNames = CAUSE_METHOD_NAMES; } for (final String methodName : methodNames) { if (methodName != null) { final Throwable cause = getCauseUsingMethodName(throwable, methodName); if (cause != null) { return cause; } } } return null; } /** *

Introspects the Throwable to obtain the root cause.

* *

This method walks through the exception chain to the last element, * "root" of the tree, using {@link #getCause(Throwable)}, and * returns that exception.

* *

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.

* * @param throwable the throwable to get the root cause for, may be null * @return the root cause of the Throwable, * null if none found or null throwable input */ public static Throwable getRootCause(final Throwable throwable) { final List list = getThrowableList(throwable); return list.size() < 2 ? null : (Throwable)list.get(list.size() - 1); } /** *

Finds a Throwable by method name.

* * @param throwable the exception to examine * @param methodName the name of the method to find and invoke * @return the wrapped exception, or null if not found */ // TODO: Remove in Lang 4.0 private static Throwable getCauseUsingMethodName(final Throwable throwable, final String methodName) { Method method = null; try { method = throwable.getClass().getMethod(methodName); } catch (final NoSuchMethodException ignored) { // NOPMD // exception ignored } catch (final SecurityException ignored) { // NOPMD // exception ignored } if (method != null && Throwable.class.isAssignableFrom(method.getReturnType())) { try { return (Throwable) method.invoke(throwable); } catch (final IllegalAccessException ignored) { // NOPMD // exception ignored } catch (final IllegalArgumentException ignored) { // NOPMD // exception ignored } catch (final InvocationTargetException ignored) { // NOPMD // exception ignored } } return null; } //----------------------------------------------------------------------- /** *

Counts the number of Throwable objects in the * exception chain.

* *

A throwable without cause will return 1. * A throwable with one cause will return 2 and so on. * A null throwable will return 0.

* *

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.

* * @param throwable the throwable to inspect, may be null * @return the count of throwables, zero if null input */ public static int getThrowableCount(final Throwable throwable) { return getThrowableList(throwable).size(); } /** *

Returns the list of Throwable objects in the * exception chain.

* *

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 null throwable will return an array of size zero.

* *

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.

* * @see #getThrowableList(Throwable) * @param throwable the throwable to inspect, may be null * @return the array of throwables, never null */ public static Throwable[] getThrowables(final Throwable throwable) { final List list = getThrowableList(throwable); return list.toArray(new Throwable[list.size()]); } /** *

Returns the list of Throwable objects in the * exception chain.

* *

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 null throwable will return a list of size zero.

* *

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.

* * @param throwable the throwable to inspect, may be null * @return the list of throwables, never null * @since Commons Lang 2.2 */ public static List getThrowableList(Throwable throwable) { final List list = new ArrayList(); while (throwable != null && list.contains(throwable) == false) { list.add(throwable); throwable = ExceptionUtils.getCause(throwable); } return list; } //----------------------------------------------------------------------- /** *

Returns the (zero based) index of the first Throwable * 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.

* *

A null throwable returns -1. * A null type returns -1. * No match in the chain returns -1.

* * @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(final Throwable throwable, final Class clazz) { return indexOf(throwable, clazz, 0, false); } /** *

Returns the (zero based) index of the first Throwable * 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.

* *

A null throwable returns -1. * A null type returns -1. * No match in the chain returns -1. * A negative start index is treated as zero. * A start index greater than the number of throwables returns -1.

* * @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(final Throwable throwable, final Class clazz, final int fromIndex) { return indexOf(throwable, clazz, fromIndex, false); } //----------------------------------------------------------------------- /** *

Returns the (zero based) index of the first Throwable * 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.

* *

A null throwable returns -1. * A null type returns -1. * No match in the chain returns -1.

* * @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(final Throwable throwable, final Class type) { return indexOf(throwable, type, 0, true); } /** *

Returns the (zero based) index of the first Throwable * 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.

* *

A null throwable returns -1. * A null type returns -1. * No match in the chain returns -1. * A negative start index is treated as zero. * A start index greater than the number of throwables returns -1.

* * @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(final Throwable throwable, final Class type, final int fromIndex) { return indexOf(throwable, type, fromIndex, true); } /** *

Worker method for the indexOfType methods.

* * @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 true, compares with {@link Class#isAssignableFrom(Class)}, otherwise compares * using references * @return index of the type within throwables nested within the specified throwable */ private static int indexOf(final Throwable throwable, final Class type, int fromIndex, final boolean subclass) { if (throwable == null || type == null) { return -1; } if (fromIndex < 0) { fromIndex = 0; } final Throwable[] throwables = ExceptionUtils.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; } //----------------------------------------------------------------------- /** *

Prints a compact stack trace for the root cause of a throwable * to System.err.

* *

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.

* *

The output of this method is consistent across JDK versions. * Note that this is the opposite order to the JDK1.4 display.

* *

The method is equivalent to printStackTrace for throwables * that don't have nested causes.

* * @param throwable the throwable to output * @since 2.0 */ public static void printRootCauseStackTrace(final Throwable throwable) { printRootCauseStackTrace(throwable, System.err); } /** *

Prints a compact stack trace for the root cause of a throwable.

* *

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.

* *

The output of this method is consistent across JDK versions. * Note that this is the opposite order to the JDK1.4 display.

* *

The method is equivalent to printStackTrace for throwables * that don't have nested causes.

* * @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 null * @since 2.0 */ public static void printRootCauseStackTrace(final Throwable throwable, final PrintStream stream) { if (throwable == null) { return; } if (stream == null) { throw new IllegalArgumentException("The PrintStream must not be null"); } final String trace[] = getRootCauseStackTrace(throwable); for (final String element : trace) { stream.println(element); } stream.flush(); } /** *

Prints a compact stack trace for the root cause of a throwable.

* *

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.

* *

The output of this method is consistent across JDK versions. * Note that this is the opposite order to the JDK1.4 display.

* *

The method is equivalent to printStackTrace for throwables * that don't have nested causes.

* * @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 null * @since 2.0 */ public static void printRootCauseStackTrace(final Throwable throwable, final PrintWriter writer) { if (throwable == null) { return; } if (writer == null) { throw new IllegalArgumentException("The PrintWriter must not be null"); } final String trace[] = getRootCauseStackTrace(throwable); for (final String element : trace) { writer.println(element); } writer.flush(); } //----------------------------------------------------------------------- /** *

Creates a compact stack trace for the root cause of the supplied * Throwable.

* *

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.

* * @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(final Throwable throwable) { if (throwable == null) { return ArrayUtils.EMPTY_STRING_ARRAY; } final Throwable throwables[] = getThrowables(throwable); final int count = throwables.length; final List frames = new ArrayList(); List nextTrace = getStackFrameList(throwables[count - 1]); for (int i = count; --i >= 0;) { final List 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[frames.size()]); } /** *

Removes common frames from the cause trace given the two stack traces.

* * @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(final List causeFrames, final List 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 final String causeFrame = causeFrames.get(causeFrameIndex); final String wrapperFrame = wrapperFrames.get(wrapperFrameIndex); if (causeFrame.equals(wrapperFrame)) { causeFrames.remove(causeFrameIndex); } causeFrameIndex--; wrapperFrameIndex--; } } //----------------------------------------------------------------------- /** *

Gets the stack trace from a Throwable as a String.

* *

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.

* * @param throwable the Throwable to be examined * @return the stack trace as generated by the exception's * printStackTrace(PrintWriter) method */ public static String getStackTrace(final Throwable throwable) { final StringWriter sw = new StringWriter(); final PrintWriter pw = new PrintWriter(sw, true); throwable.printStackTrace(pw); return sw.getBuffer().toString(); } /** *

Captures the stack trace associated with the specified * Throwable object, decomposing it into a list of * stack frames.

* *

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.

* * @param throwable the Throwable to examine, may be null * @return an array of strings describing each stack frame, never null */ public static String[] getStackFrames(final Throwable throwable) { if (throwable == null) { return ArrayUtils.EMPTY_STRING_ARRAY; } return getStackFrames(getStackTrace(throwable)); } //----------------------------------------------------------------------- /** *

Returns an array where each element is a line from the argument.

* *

The end of line is determined by the value of {@link SystemUtils#LINE_SEPARATOR}.

* * @param stackTrace a stack trace String * @return an array where each element is a line from the argument */ static String[] getStackFrames(final String stackTrace) { final String linebreak = SystemUtils.LINE_SEPARATOR; final StringTokenizer frames = new StringTokenizer(stackTrace, linebreak); final List list = new ArrayList(); while (frames.hasMoreTokens()) { list.add(frames.nextToken()); } return list.toArray(new String[list.size()]); } /** *

Produces a List of stack frames - the message * is not included. Only the trace of the specified exception is * returned, any caused by trace is stripped.

* *

This works in most cases - it will only fail if the exception * message contains a line that starts with: * "   at".

* * @param t is any throwable * @return List of stack frames */ static List getStackFrameList(final Throwable t) { final String stackTrace = getStackTrace(t); final String linebreak = SystemUtils.LINE_SEPARATOR; final StringTokenizer frames = new StringTokenizer(stackTrace, linebreak); final List list = new ArrayList(); boolean traceStarted = false; while (frames.hasMoreTokens()) { final String token = frames.nextToken(); // Determine if the line starts with at final int at = token.indexOf("at"); if (at != -1 && token.substring(0, at).trim().isEmpty()) { traceStarted = true; list.add(token); } else if (traceStarted) { break; } } return list; } //----------------------------------------------------------------------- /** * Gets a short message summarising the exception. *

* 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(final Throwable th) { if (th == null) { return ""; } final String clsName = ClassUtils.getShortClassName(th, null); final String msg = th.getMessage(); return clsName + ": " + StringUtils.defaultString(msg); } //----------------------------------------------------------------------- /** * Gets a short message summarising the root cause exception. *

* 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(final Throwable th) { Throwable root = ExceptionUtils.getRootCause(th); root = root == null ? th : root; return getMessage(root); } }





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