ExceptionUtils.java
package org.codehaus.plexus.util;
/* ====================================================================
* The Apache Software License, Version 1.1
*
* Copyright (c) 2002-2003 The Apache Software Foundation. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution, if
* any, must include the following acknowledgement:
* "This product includes software developed by the
* Apache Software Foundation (http://www.codehaus.org/)."
* Alternately, this acknowledgement may appear in the software itself,
* if and wherever such third-party acknowledgements normally appear.
*
* 4. The names "The Jakarta Project", "Commons", and "Apache Software
* Foundation" must not be used to endorse or promote products derived
* from this software without prior written permission. For written
* permission, please contact codehaus@codehaus.org.
*
* 5. Products derived from this software may not be called "Apache"
* nor may "Apache" appear in their names without prior written
* permission of the Apache Software Foundation.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* <http://www.codehaus.org/>.
*/
import java.io.PrintStream;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;
import java.util.StringTokenizer;
/**
* <p>
* <code>ExceptionUtils</code> provides utilities for manipulating <code>Throwable</code> objects.
* </p>
*
* @author <a href="mailto:dlr@finemaltcoding.com">Daniel Rall</a>
* @author Dmitri Plotnikov
* @author Stephen Colebourne
* @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.
*/
static final String WRAPPED_MARKER = " [wrapped] ";
/**
* The names of methods commonly used to access a wrapped exception.
*/
protected static String[] CAUSE_METHOD_NAMES = {
"getCause",
"getNextException",
"getTargetException",
"getException",
"getSourceException",
"getRootCause",
"getCausedByException",
"getNested"
};
/**
* Constructs a new <code>ExceptionUtils</code>. Protected to discourage instantiation.
*/
protected ExceptionUtils() {}
/**
* <p>
* Adds to the list of method names used in the search for <code>Throwable</code> objects.
* </p>
*
* @param methodName the methodName to add to the list, null and empty strings are ignored
*/
public static void addCauseMethodName(String methodName) {
if (methodName != null && methodName.length() > 0) {
List<String> list = new ArrayList<String>(Arrays.asList(CAUSE_METHOD_NAMES));
list.add(methodName);
CAUSE_METHOD_NAMES = list.toArray(new String[0]);
}
}
/**
* <p>
* Introspects the specified <code>Throwable</code> to obtain the cause.
* </p>
* <p>
* The method searches for methods with specific names that return a <code>Throwable</code> object. This will pick
* up most wrapping exceptions, including those from JDK 1.4, and The method names can be added to using
* {@link #addCauseMethodName(String)}. The default list searched for are:
* </p>
* <ul>
* <li><code>getCause()</code>
* <li><code>getNextException()</code>
* <li><code>getTargetException()</code>
* <li><code>getException()</code>
* <li><code>getSourceException()</code>
* <li><code>getRootCause()</code>
* <li><code>getCausedByException()</code>
* <li><code>getNested()</code>
* </ul>
* <p>
* In the absence of any such method, the object is inspected for a <code>detail</code> field assignable to a
* <code>Throwable</code>.
* </p>
* <p>
* If none of the above is found, returns <code>null</code>.
* </p>
*
* @param throwable The exception to introspect for a cause.
* @return The cause of the <code>Throwable</code>.
* @throws NullPointerException if the throwable is null
*/
public static Throwable getCause(Throwable throwable) {
return getCause(throwable, CAUSE_METHOD_NAMES);
}
/**
* <p>
* Introspects the specified <code>Throwable</code> to obtain the cause using a supplied array of method names.
* </p>
*
* @param throwable The exception to introspect for a cause.
* @param methodNames the methods names to match
* @return The cause of the <code>Throwable</code>.
* @throws NullPointerException if the method names array is null or contains null
* @throws NullPointerException if the throwable is null
*/
public static Throwable getCause(Throwable throwable, String[] methodNames) {
Throwable cause = getCauseUsingWellKnownTypes(throwable);
if (cause == null) {
for (String methodName : methodNames) {
cause = getCauseUsingMethodName(throwable, methodName);
if (cause != null) {
break;
}
}
if (cause == null) {
cause = getCauseUsingFieldName(throwable, "detail");
}
}
return cause;
}
/**
* <p>
* Walks through the exception chain to the last element -- the "root" of the tree -- using
* {@link #getCause(Throwable)}, and returns that exception.
* </p>
*
* @param throwable the throwable to get the root cause for
* @return The root cause of the <code>Throwable</code>.
*/
public static Throwable getRootCause(Throwable throwable) {
Throwable cause = getCause(throwable);
if (cause != null) {
throwable = cause;
while ((throwable = getCause(throwable)) != null) {
cause = throwable;
}
}
return cause;
}
/**
* <p>
* Uses <code>instanceof</code> checks to examine the exception, looking for well known types which could contain
* chained or wrapped exceptions.
* </p>
*
* @param throwable the exception to examine
* @return The wrapped exception, or <code>null</code> if not found.
*/
private static Throwable getCauseUsingWellKnownTypes(Throwable throwable) {
if (throwable instanceof SQLException) {
return ((SQLException) throwable).getNextException();
} else if (throwable instanceof InvocationTargetException) {
return ((InvocationTargetException) throwable).getTargetException();
} else {
return null;
}
}
/**
* <p>
* Find a throwable by method name.
* </p>
*
* @param throwable the exception to examine
* @param methodName the name of the method to find and invoke
* @return The wrapped exception, or <code>null</code> if not found.
*/
private static Throwable getCauseUsingMethodName(Throwable throwable, String methodName) {
Method method = null;
try {
method = throwable.getClass().getMethod(methodName, null);
} catch (NoSuchMethodException ignored) {
} catch (SecurityException ignored) {
}
if (method != null && Throwable.class.isAssignableFrom(method.getReturnType())) {
try {
return (Throwable) method.invoke(throwable, new Object[0]);
} catch (IllegalAccessException ignored) {
} catch (IllegalArgumentException ignored) {
} catch (InvocationTargetException ignored) {
}
}
return null;
}
/**
* <p>
* Find a throwable by field name.
* </p>
*
* @param throwable the exception to examine
* @param fieldName the name of the attribute to examine
* @return The wrapped exception, or <code>null</code> if not found.
*/
private static Throwable getCauseUsingFieldName(Throwable throwable, String fieldName) {
Field field = null;
try {
field = throwable.getClass().getField(fieldName);
} catch (NoSuchFieldException ignored) {
} catch (SecurityException ignored) {
}
if (field != null && Throwable.class.isAssignableFrom(field.getType())) {
try {
return (Throwable) field.get(throwable);
} catch (IllegalAccessException ignored) {
} catch (IllegalArgumentException ignored) {
}
}
return null;
}
/**
* <p>
* Returns the number of <code>Throwable</code> objects in the exception chain.
* </p>
*
* @param throwable the exception to inspect
* @return The throwable count.
*/
public static int getThrowableCount(Throwable throwable) {
// Count the number of throwables
int count = 0;
while (throwable != null) {
count++;
throwable = ExceptionUtils.getCause(throwable);
}
return count;
}
/**
* <p>
* Returns the list of <code>Throwable</code> objects in the exception chain.
* </p>
*
* @param throwable the exception to inspect
* @return The list of <code>Throwable</code> objects.
*/
public static Throwable[] getThrowables(Throwable throwable) {
List<Throwable> list = new ArrayList<>();
while (throwable != null) {
list.add(throwable);
throwable = getCause(throwable);
}
return list.toArray(new Throwable[0]);
}
/**
* <p>
* Delegates to {@link #indexOfThrowable(Throwable, Class, int)}, starting the search at the beginning of the
* exception chain.
* </p>
* @param throwable the exception to inspect
* @param type <code>Class</code> to look for
* @return index of the stack matching the type
* @see #indexOfThrowable(Throwable, Class, int)
*/
public static int indexOfThrowable(Throwable throwable, Class type) {
return indexOfThrowable(throwable, type, 0);
}
/**
* <p>
* Returns the (zero based) index, of the first <code>Throwable</code> that matches the specified type in the
* exception chain of <code>Throwable</code> objects with an index greater than or equal to the specified index, or
* <code>-1</code> if the type is not found.
* </p>
*
* @param throwable the exception to inspect
* @param type <code>Class</code> to look for
* @param fromIndex the (zero based) index of the starting position in the chain to be searched
* @return the first occurrence of the type in the chain, or <code>-1</code> if the type is not found
* @throws IndexOutOfBoundsException If the <code>fromIndex</code> argument is negative or not less than the count
* of <code>Throwable</code>s in the chain.
*/
public static int indexOfThrowable(Throwable throwable, Class type, int fromIndex) {
if (fromIndex < 0) {
throw new IndexOutOfBoundsException("Throwable index out of range: " + fromIndex);
}
Throwable[] throwables = ExceptionUtils.getThrowables(throwable);
if (fromIndex >= throwables.length) {
throw new IndexOutOfBoundsException("Throwable index out of range: " + fromIndex);
}
for (int i = fromIndex; i < throwables.length; i++) {
if (throwables[i].getClass().equals(type)) {
return i;
}
}
return -1;
}
/**
* 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.
* <p>
* The method is equivalent to t.printStackTrace() for throwables that don't have nested causes.
* @param t the exception
* @param stream the stream
*/
public static void printRootCauseStackTrace(Throwable t, PrintStream stream) {
String trace[] = getRootCauseStackTrace(t);
for (String aTrace : trace) {
stream.println(aTrace);
}
stream.flush();
}
/**
* Equivalent to printRootCauseStackTrace(t, System.err)
* @param t the exception
*/
public static void printRootCauseStackTrace(Throwable t) {
printRootCauseStackTrace(t, System.err);
}
/**
* Same as printRootCauseStackTrace(t, stream), except it takes a PrintWriter as an argument.
* @param t the cause
* @param writer the writer
*/
public static void printRootCauseStackTrace(Throwable t, PrintWriter writer) {
String trace[] = getRootCauseStackTrace(t);
for (String aTrace : trace) {
writer.println(aTrace);
}
writer.flush();
}
/**
* Creates a compact stack trace for the root cause of the supplied throwable. See
* <code>printRootCauseStackTrace(Throwable t, PrintStream s)</code>
* @param t the cause
* @return the Stack
*/
public static String[] getRootCauseStackTrace(Throwable t) {
Throwable[] throwables = getThrowables(t);
int count = throwables.length;
ArrayList<String> frames = new ArrayList<>();
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 (String aTrace : trace) {
frames.add(aTrace);
}
}
return frames.toArray(new String[0]);
}
/**
* Given two stack traces, removes common frames from the cause trace.
*
* @param causeFrames stack trace of a cause throwable
* @param wrapperFrames stack trace of a wrapper throwable
*/
private static void removeCommonFrames(List<String> causeFrames, List<String> wrapperFrames) {
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--;
}
}
/**
* A convenient way of extracting the stack trace from an exception.
*
* @param t The <code>Throwable</code>.
* @return The stack trace as generated by the exception's <code>printStackTrace(PrintWriter)</code> method.
*/
public static String getStackTrace(Throwable t) {
StringWriter sw = new StringWriter();
PrintWriter pw = new PrintWriter(sw, true);
t.printStackTrace(pw);
return sw.getBuffer().toString();
}
/**
* A way to get the entire nested stack-trace of an throwable.
*
* @param t The <code>Throwable</code>.
* @return The nested stack trace, with the root cause first.
*/
public static String getFullStackTrace(Throwable t) {
StringWriter sw = new StringWriter();
PrintWriter pw = new PrintWriter(sw, true);
Throwable[] ts = getThrowables(t);
for (Throwable t1 : ts) {
t1.printStackTrace(pw);
if (isNestedThrowable(t1)) {
break;
}
}
return sw.getBuffer().toString();
}
/**
* Whether an Throwable is considered nested or not.
*
* @param throwable The <code>Throwable</code>.
* @return boolean true/false
*/
public static boolean isNestedThrowable(Throwable throwable) {
if (throwable == null) {
return false;
}
if (throwable instanceof SQLException) {
return true;
} else if (throwable instanceof InvocationTargetException) {
return true;
}
for (String CAUSE_METHOD_NAME : CAUSE_METHOD_NAMES) {
try {
Method method = throwable.getClass().getMethod(CAUSE_METHOD_NAME, null);
if (method != null) {
return true;
}
} catch (NoSuchMethodException ignored) {
} catch (SecurityException ignored) {
}
}
try {
Field field = throwable.getClass().getField("detail");
if (field != null) {
return true;
}
} catch (NoSuchFieldException ignored) {
} catch (SecurityException ignored) {
}
return false;
}
/**
* Captures the stack trace associated with the specified <code>Throwable</code> object, decomposing it into a list
* of stack frames.
*
* @param t The <code>Throwable</code>.
* @return An array of strings describing each stack frame.
*/
public static String[] getStackFrames(Throwable t) {
return getStackFrames(getStackTrace(t));
}
/**
* Functionality shared between the <code>getStackFrames(Throwable)</code> methods of this and the classes.
*/
static String[] getStackFrames(String stackTrace) {
String linebreak = System.getProperty("line.separator");
StringTokenizer frames = new StringTokenizer(stackTrace, linebreak);
List<String> list = new LinkedList<String>();
while (frames.hasMoreTokens()) {
list.add(frames.nextToken());
}
return list.toArray(new String[0]);
}
/**
* Produces a List of stack frames - the message is not included. 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<String> getStackFrameList(Throwable t) {
String stackTrace = getStackTrace(t);
String linebreak = System.getProperty("line.separator");
StringTokenizer frames = new StringTokenizer(stackTrace, linebreak);
List<String> list = new LinkedList<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;
}
}