/*
* 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;
/**
* <p>Provides utilities for manipulating and examining
* <code>Throwable</code> objects.</p>
*
* @since 1.0
* @version $Id: ExceptionUtils.java 1199894 2011-11-09 17:53:59Z ggregory $
*/
public class ExceptionUtils {
/**
* <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] ";
/**
* <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",
};
/**
* <p>
* Public constructor allows an instance of <code>ExceptionUtils</code> to be created, although that is not
* normally necessary.
* </p>
*/
public ExceptionUtils() {
super();
}
//-----------------------------------------------------------------------
/**
* <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);
}
//-----------------------------------------------------------------------
/**
* <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
*/
@Deprecated
public static Throwable getCause(Throwable throwable) {
return getCause(throwable, CAUSE_METHOD_NAMES);
}
/**
* <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
*/
@Deprecated
public static Throwable getCause(Throwable throwable, String[] methodNames) {
if (throwable == null) {
return null;
}
if (methodNames == null) {
methodNames = CAUSE_METHOD_NAMES;
}
for (String methodName : methodNames) {
if (methodName != null) {
Throwable cause = getCauseUsingMethodName(throwable, methodName);
if (cause != null) {
return cause;
}
}
}
return null;
}
/**
* <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 : (Throwable)list.get(list.size() - 1);
}
/**
* <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(Throwable throwable, String methodName) {
Method method = null;
try {
method = throwable.getClass().getMethod(methodName);
} catch (NoSuchMethodException ignored) { // NOPMD
// exception ignored
} catch (SecurityException ignored) { // NOPMD
// exception ignored
}
if (method != null && Throwable.class.isAssignableFrom(method.getReturnType())) {
try {
return (Throwable) method.invoke(throwable);
} catch (IllegalAccessException ignored) { // NOPMD
// exception ignored
} catch (IllegalArgumentException ignored) { // NOPMD
// exception ignored
} catch (InvocationTargetException ignored) { // NOPMD
// exception ignored
}
}
return null;
}
//-----------------------------------------------------------------------
/**
* <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 = ExceptionUtils.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 = 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;
}
//-----------------------------------------------------------------------
/**
* <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 (String element : trace) {
stream.println(element);
}
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 (String element : trace) {
writer.println(element);
}
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 ArrayUtils.EMPTY_STRING_ARRAY;
}
Throwable throwables[] = getThrowables(throwable);
int count = throwables.length;
List<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[frames.size()]);
}
/**
* <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>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 ArrayUtils.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>
*
* @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 = SystemUtils.LINE_SEPARATOR;
StringTokenizer frames = new StringTokenizer(stackTrace, linebreak);
List<String> list = new ArrayList<String>();
while (frames.hasMoreTokens()) {
list.add(frames.nextToken());
}
return list.toArray(new String[list.size()]);
}
/**
* <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 = SystemUtils.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 = ClassUtils.getShortClassName(th, null);
String msg = th.getMessage();
return clsName + ": " + StringUtils.defaultString(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 = ExceptionUtils.getRootCause(th);
root = root == null ? th : root;
return getMessage(root);
}
}