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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.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
*/
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, 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.
*
* @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, 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 {@link 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.
*
* @param throwable the throwable to get the root cause for, may be null
* @return the root cause of the Throwable,
* null if null throwable input
*/
public static Throwable getRootCause(final Throwable throwable) {
final List list = getThrowableList(throwable);
return list.isEmpty() ? null : 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 | 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.
*
* @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 2.2
*/
public static List getThrowableList(Throwable throwable) {
final List 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
* {@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 = 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;
}
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.
*
* @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;
}
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.
*
* @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());
}
frames.addAll(trace);
}
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 System#lineSeparator()}.
*
* @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 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 = System.lineSeparator();
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 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}
*
* @param th the throwable to get a message for, null returns empty string
* @return the message, non-null
* @since 2.2
*/
public static String getRootCauseMessage(final Throwable th) {
Throwable root = 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.
*
* @param throwable
* The throwable to rethrow.
* @param 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 rethrow(final Throwable throwable) {
// claim that the typeErasure invocation throws a RuntimeException
return ExceptionUtils.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.
*/
@SuppressWarnings("unchecked")
private static 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.
*
* @param throwable
* The throwable to rethrow.
* @param 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 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?
*
* @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 type) {
if (chain instanceof UndeclaredThrowableException) {
chain = chain.getCause();
}
return type.isInstance(chain);
}
}