/*
 * 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.lang.reflect.UndeclaredThrowableException;
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.Validate;

Provides utilities for manipulating and examining
Throwable objects.
Since:
1.0/**
 * <p>Provides utilities for manipulating and examining
 * <code>Throwable</code> objects.</p>
 *
 * @since 1.0
 */
public class ExceptionUtils {

    
Used when printing stack frames to denote the start of a
wrapped exception.
Package private for accessibility by test suite.
/**
     * <p>Used when printing stack frames to denote the start of a
     * wrapped exception.</p>
     *
     * <p>Package private for accessibility by test suite.</p>
     */
    static final String WRAPPED_MARKER = " [wrapped] ";

    
The names of methods commonly used to access a wrapped exception.
/**
     * <p>The names of methods commonly used to access a wrapped exception.</p>
     */
    // 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.

/**
     * <p>
     * Public constructor allows an instance of <code>ExceptionUtils</code> to be created, although that is not
     * normally necessary.
     * </p>
     */
    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.
Returns:
cloned array of the default method names
Since:
3.0
Deprecated:
This feature will be removed in Lang 4.0/**
     * <p>Returns the default names used when searching for the cause of an exception.</p>
     *
     * <p>This may be modified and used in the overloaded getCause(Throwable, String[]) method.</p>
     *
     * @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.
Params:
throwable –  the throwable to introspect for a cause, may be null
Returns:
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, use Throwable.getCause instead/**
     * <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.
     *
     * <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>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
     * @deprecated This feature will be removed in Lang 4.0, use {@link Throwable#getCause} instead
     */
    @Deprecated
    public static Throwable getCause(final Throwable throwable) {
        return getCause(throwable, null);
    }

    
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.
Params:
throwable –  the throwable to introspect for a cause, may be null
methodNames –  the method names, null treated as default set
Returns:
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, use Throwable.getCause instead/**
     * <p>Introspects the <code>Throwable</code> to obtain the cause.</p>
     *
     * <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
     * @deprecated This feature will be removed in Lang 4.0, use {@link Throwable#getCause} instead
     */
    @Deprecated
    public static Throwable getCause(final Throwable throwable, String[] methodNames) {
        if (throwable == null) {
            return null;
        }

        if (methodNames == null) {
            final Throwable cause = throwable.getCause();
            if (cause != null) {
                return cause;
            }

            methodNames = CAUSE_METHOD_NAMES;
        }

        for (final String methodName : methodNames) {
            if (methodName != null) {
                final Throwable legacyCause = getCauseUsingMethodName(throwable, methodName);
                if (legacyCause != null) {
                    return legacyCause;
                }
            }
        }

        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 Throwable.getCause(), 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.
Params:
throwable –  the throwable to get the root cause for, may be null
Returns:
the root cause of the Throwable,
 null if none found or null throwable input/**
     * <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 Throwable#getCause()}, 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(final Throwable throwable) {
        final List<Throwable> list = getThrowableList(throwable);
        return list.size() < 2 ? null : list.get(list.size() - 1);
    }

    
Finds a Throwable by method name.
Params:
throwable –  the exception to examine
methodName –  the name of the method to find and invoke
Returns:
the wrapped exception, or null if not found/**
     * <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
     */
    // 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 | SecurityException ignored) { // NOPMD
            // exception ignored
        }

        if (method != null && Throwable.class.isAssignableFrom(method.getReturnType())) {
            try {
                return (Throwable) method.invoke(throwable);
            } catch (final IllegalAccessException | IllegalArgumentException | 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.
Params:
throwable –  the throwable to inspect, may be null
Returns:
the count of throwables, zero if null input/**
     * <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(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.
Params:
throwable –  the throwable to inspect, may be null
See Also:
getThrowableList(Throwable)
Returns:
the array of throwables, never null/**
     * <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(final Throwable throwable) {
        final List<Throwable> 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.
Params:
throwable –  the throwable to inspect, may be null
Returns:
the list of throwables, never null
Since:
Commons Lang 2.2/**
     * <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) {
        final List<Throwable> list = new ArrayList<>();
        while (throwable != null && !list.contains(throwable)) {
            list.add(throwable);
            throwable = throwable.getCause();
        }
        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 indexOfType(Throwable, Class<?>) for the opposite.
A null throwable returns -1.
A null type returns -1.
No match in the chain returns -1.
Params:
throwable –  the throwable to inspect, may be null
clazz –  the class to search for, subclasses do not match, null returns -1
Returns:
the index into the throwable chain, -1 if no match or null input/**
     * <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(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 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.
Params:
throwable –  the throwable to inspect, may be null
clazz –  the class to search for, subclasses do not match, null returns -1
fromIndex –  the (zero based) index of the starting position,
 negative treated as zero, larger than chain size returns -1
Returns:
the index into the throwable chain, -1 if no match or null input/**
     * <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(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 indexOfThrowable(Throwable, Class<?>) for the opposite.
A null throwable returns -1.
A null type returns -1.
No match in the chain returns -1.
Params:
throwable –  the throwable to inspect, may be null
type –  the type to search for, subclasses match, null returns -1
Returns:
the index into the throwable chain, -1 if no match or null input
Since:
2.1/**
     * <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(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 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.
Params:
throwable –  the throwable to inspect, may be null
type –  the type to search for, subclasses match, null returns -1
fromIndex –  the (zero based) index of the starting position,
 negative treated as zero, larger than chain size returns -1
Returns:
the index into the throwable chain, -1 if no match or null input
Since:
2.1/**
     * <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(final Throwable throwable, final Class<?> type, final int fromIndex) {
        return indexOf(throwable, type, fromIndex, true);
    }

    
Worker method for the indexOfType methods.
Params:
throwable –  the throwable to inspect, may be null
type –  the type to search for, subclasses match, null returns -1
fromIndex –  the (zero based) index of the starting position,
 negative treated as zero, larger than chain size returns -1
subclass – if true, compares with Class.isAssignableFrom(Class), otherwise compares using references
Returns:
index of the type within throwables nested within the specified throwable/**
     * <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 within the specified <code>throwable</code>
     */
    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.
Params:
throwable –  the throwable to output
Since:
2.0/**
     * <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(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.
Params:
throwable –  the throwable to output, may be null
stream –  the stream to output to, may not be null
Throws:
IllegalArgumentException – if the stream is null
Since:
2.0/**
     * <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(final Throwable throwable, final PrintStream stream) {
        if (throwable == null) {
            return;
        }
        Validate.isTrue(stream != null, "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.
Params:
throwable –  the throwable to output, may be null
writer –  the writer to output to, may not be null
Throws:
IllegalArgumentException – if the writer is null
Since:
2.0/**
     * <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(final Throwable throwable, final PrintWriter writer) {
        if (throwable == null) {
            return;
        }
        Validate.isTrue(writer != null, "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.
Params:
throwable –  the throwable to examine, may be null
Returns:
an array of stack trace frames, never null
Since:
2.0/**
     * <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(final Throwable throwable) {
        if (throwable == null) {
            return ArrayUtils.EMPTY_STRING_ARRAY;
        }
        final Throwable throwables[] = getThrowables(throwable);
        final int count = throwables.length;
        final List<String> frames = new ArrayList<>();
        List<String> nextTrace = getStackFrameList(throwables[count - 1]);
        for (int i = count; --i >= 0;) {
            final 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());
            }
            frames.addAll(trace);
        }
        return frames.toArray(new String[frames.size()]);
    }

    
Removes common frames from the cause trace given the two stack traces.
Params:
causeFrames –  stack trace of a cause throwable
wrapperFrames –  stack trace of a wrapper throwable
Throws:
IllegalArgumentException – if either argument is null
Since:
2.0/**
     * <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(final List<String> causeFrames, final 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
            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 Throwable.printStackTrace(PrintWriter). On JDK1.3 and earlier, the cause exception will not be shown unless the specified throwable alters printStackTrace.
Params:
throwable –  the Throwable to be examined
Returns:
the stack trace as generated by the exception's
 printStackTrace(PrintWriter) method/**
     * <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(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 Throwable.printStackTrace(PrintWriter). On JDK1.3 and earlier, the cause exception will not be shown unless the specified throwable alters printStackTrace.
Params:
throwable –  the Throwable to examine, may be null
Returns:
an array of strings describing each stack frame, never null/**
     * <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(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 System.lineSeparator().
Params:
stackTrace –  a stack trace String
Returns:
an array where each element is a line from the argument/**
     * <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 System#lineSeparator()}.</p>
     *
     * @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 = System.lineSeparator();
        final StringTokenizer frames = new StringTokenizer(stackTrace, linebreak);
        final List<String> 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".
Params:
t – is any throwable
Returns:
List of stack frames/**
     * <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>&quot;&nbsp;&nbsp;&nbsp;at&quot;.</code></p>
     *
     * @param t is any throwable
     * @return List of stack frames
     */
    static List<String> getStackFrameList(final Throwable t) {
        final String stackTrace = getStackTrace(t);
        final String linebreak = System.lineSeparator();
        final StringTokenizer frames = new StringTokenizer(stackTrace, linebreak);
        final List<String> list = new ArrayList<>();
        boolean traceStarted = false;
        while (frames.hasMoreTokens()) {
            final String token = frames.nextToken();
            // Determine if the line starts with <whitespace>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}
Params:
th –  the throwable to get a message for, null returns empty string
Returns:
the message, non-null
Since:
Commons Lang 2.2/**
     * 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(final Throwable th) {
        if (th == null) {
            return StringUtils.EMPTY;
        }
        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}
Params:
th –  the throwable to get a message for, null returns empty string
Returns:
the message, non-null
Since:
Commons Lang 2.2/**
     * 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(final Throwable th) {
        Throwable root = ExceptionUtils.getRootCause(th);
        root = root == null ? th : root;
        return getMessage(root);
    }

    
Throw a checked exception without adding the exception to the throws
clause of the calling method. This method prevents throws clause
pollution and reduces the clutter of "Caused by" exceptions in the
stacktrace.

The use of this technique may be controversial, but exceedingly useful to
library developers.

 public int propagateExample { // note that there is no throws clause
     try {
         return invocation(); // throws IOException
     } catch (Exception e) {
         return ExceptionUtils.rethrow(e);  // propagates a checked exception
     }
 }


This is an alternative to the more conservative approach of wrapping the
checked exception in a RuntimeException:

 public int wrapExample { // note that there is no throws clause
     try {
         return invocation(); // throws IOException
     } catch (Error e) {
         throw e;
     } catch (RuntimeException e) {
         throw e;  // wraps a checked exception
     } catch (Exception e) {
         throw new UndeclaredThrowableException(e);  // wraps a checked exception
     }
 }


One downside to using this approach is that the java compiler will not
allow invoking code to specify a checked exception in a catch clause
unless there is some code path within the try block that has invoked a
method declared with that checked exception. If the invoking site wishes
to catch the shaded checked exception, it must either invoke the shaded
code through a method re-declaring the desired checked exception, or
catch Exception and use the instanceof operator. Either of these
techniques are required when interacting with non-java jvm code such as
Jython, Scala, or Groovy, since these languages do not consider any
exceptions as checked.
Params:
throwable – 
           The throwable to rethrow.
Type parameters:
<R> – The type of the returned value.
See Also:
wrapAndThrow(Throwable)
Returns:
Never actually returned, this generic type matches any type
        which the calling site requires. "Returning" the results of this
        method, as done in the propagateExample above, will satisfy the
        java compiler requirement that all code paths return a value.
Since:
3.5/**
     * Throw a checked exception without adding the exception to the throws
     * clause of the calling method. This method prevents throws clause
     * pollution and reduces the clutter of "Caused by" exceptions in the
     * stacktrace.
     * <p>
     * The use of this technique may be controversial, but exceedingly useful to
     * library developers.
     * <code>
     *  public int propagateExample { // note that there is no throws clause
     *      try {
     *          return invocation(); // throws IOException
     *      } catch (Exception e) {
     *          return ExceptionUtils.rethrow(e);  // propagates a checked exception
     *      }
     *  }
     * </code>
     * <p>
     * This is an alternative to the more conservative approach of wrapping the
     * checked exception in a RuntimeException:
     * <code>
     *  public int wrapExample { // note that there is no throws clause
     *      try {
     *          return invocation(); // throws IOException
     *      } catch (Error e) {
     *          throw e;
     *      } catch (RuntimeException e) {
     *          throw e;  // wraps a checked exception
     *      } catch (Exception e) {
     *          throw new UndeclaredThrowableException(e);  // wraps a checked exception
     *      }
     *  }
     * </code>
     * <p>
     * One downside to using this approach is that the java compiler will not
     * allow invoking code to specify a checked exception in a catch clause
     * unless there is some code path within the try block that has invoked a
     * method declared with that checked exception. If the invoking site wishes
     * to catch the shaded checked exception, it must either invoke the shaded
     * code through a method re-declaring the desired checked exception, or
     * catch Exception and use the instanceof operator. Either of these
     * techniques are required when interacting with non-java jvm code such as
     * Jython, Scala, or Groovy, since these languages do not consider any
     * exceptions as checked.
     *
     * @param throwable
     *            The throwable to rethrow.
     * @param <R> The type of the returned value.
     * @return Never actually returned, this generic type matches any type
     *         which the calling site requires. "Returning" the results of this
     *         method, as done in the propagateExample above, will satisfy the
     *         java compiler requirement that all code paths return a value.
     * @since 3.5
     * @see #wrapAndThrow(Throwable)
     */
    public static <R> R rethrow(final Throwable throwable) {
        // claim that the typeErasure invocation throws a RuntimeException
        return ExceptionUtils.<R, RuntimeException> typeErasure(throwable);
    }

    
Claim a Throwable is another Exception type using type erasure. This
hides a checked exception from the java compiler, allowing a checked
exception to be thrown without having the exception in the method's throw
clause.
/**
     * Claim a Throwable is another Exception type using type erasure. This
     * hides a checked exception from the java compiler, allowing a checked
     * exception to be thrown without having the exception in the method's throw
     * clause.
     */
    @SuppressWarnings("unchecked")
    private static <R, T extends Throwable> R typeErasure(final Throwable throwable) throws T {
        throw (T) throwable;
    }

    
Throw a checked exception without adding the exception to the throws
clause of the calling method. For checked exceptions, this method throws
an UndeclaredThrowableException wrapping the checked exception. For
Errors and RuntimeExceptions, the original exception is rethrown.

The downside to using this approach is that invoking code which needs to
handle specific checked exceptions must sniff up the exception chain to
determine if the caught exception was caused by the checked exception.
Params:
throwable – 
           The throwable to rethrow.
Type parameters:
<R> – The type of the returned value.
See Also:
rethrow(Throwable)
hasCause(Throwable, Class<? extends Throwable>)
Returns:
Never actually returned, this generic type matches any type
        which the calling site requires. "Returning" the results of this
        method will satisfy the java compiler requirement that all code
        paths return a value.
Since:
3.5/**
     * Throw a checked exception without adding the exception to the throws
     * clause of the calling method. For checked exceptions, this method throws
     * an UndeclaredThrowableException wrapping the checked exception. For
     * Errors and RuntimeExceptions, the original exception is rethrown.
     * <p>
     * The downside to using this approach is that invoking code which needs to
     * handle specific checked exceptions must sniff up the exception chain to
     * determine if the caught exception was caused by the checked exception.
     *
     * @param throwable
     *            The throwable to rethrow.
     * @param <R> The type of the returned value.
     * @return Never actually returned, this generic type matches any type
     *         which the calling site requires. "Returning" the results of this
     *         method will satisfy the java compiler requirement that all code
     *         paths return a value.
     * @since 3.5
     * @see #rethrow(Throwable)
     * @see #hasCause(Throwable, Class)
     */
    public static <R> R wrapAndThrow(final Throwable throwable) {
        if (throwable instanceof RuntimeException) {
            throw (RuntimeException) throwable;
        }
        if (throwable instanceof Error) {
            throw (Error) throwable;
        }
        throw new UndeclaredThrowableException(throwable);
    }

    
Does the throwable's causal chain have an immediate or wrapped exception
of the given type?
Params:
chain – 
           The root of a Throwable causal chain.
type – 
           The exception type to test.
See Also:
wrapAndThrow(Throwable)
Returns:
true, if chain is an instance of type or is an
        UndeclaredThrowableException wrapping a cause.
Since:
3.5/**
     * Does the throwable's causal chain have an immediate or wrapped exception
     * of the given type?
     *
     * @param chain
     *            The root of a Throwable causal chain.
     * @param type
     *            The exception type to test.
     * @return true, if chain is an instance of type or is an
     *         UndeclaredThrowableException wrapping a cause.
     * @since 3.5
     * @see #wrapAndThrow(Throwable)
     */
    public static boolean hasCause(Throwable chain,
            final Class<? extends Throwable> type) {
        if (chain instanceof UndeclaredThrowableException) {
            chain = chain.getCause();
        }
        return type.isInstance(chain);
    }
}