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Diffstat (limited to 'src/main/java/org/apache/commons/lang3/exception/ExceptionUtils.java')
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diff --git a/src/main/java/org/apache/commons/lang3/exception/ExceptionUtils.java b/src/main/java/org/apache/commons/lang3/exception/ExceptionUtils.java new file mode 100644 index 000000000..08f038af9 --- /dev/null +++ b/src/main/java/org/apache/commons/lang3/exception/ExceptionUtils.java @@ -0,0 +1,981 @@ +/* + * 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.Collections; +import java.util.List; +import java.util.Objects; +import java.util.StringTokenizer; +import java.util.function.Consumer; +import java.util.stream.Stream; + +import org.apache.commons.lang3.ArrayUtils; +import org.apache.commons.lang3.ClassUtils; +import org.apache.commons.lang3.StringUtils; + +/** + * Provides utilities for manipulating and examining + * {@link Throwable} objects. + * + * @since 1.0 + */ +public class ExceptionUtils { + + private static final int NOT_FOUND = -1; + + /** + * 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", + }; + + /** + * Used when printing stack frames to denote the start of a + * wrapped exception. + * + * <p>Package private for accessibility by test suite.</p> + */ + static final String WRAPPED_MARKER = " [wrapped] "; + + /** + * Claims a Throwable is another Throwable 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 eraseType(final Throwable throwable) throws T { + throw (T) throwable; + } + + /** + * Introspects the {@link Throwable} to obtain the cause. + * + * <p>The method searches for methods with specific names that return a + * {@link Throwable} object. This will pick up most wrapping exceptions, + * including those from JDK 1.4. + * </p> + * + * <p>The default list searched for are:</p> + * <ul> + * <li>{@code getCause()}</li> + * <li>{@code getNextException()}</li> + * <li>{@code getTargetException()}</li> + * <li>{@code getException()}</li> + * <li>{@code getSourceException()}</li> + * <li>{@code getRootCause()}</li> + * <li>{@code getCausedByException()}</li> + * <li>{@code getNested()}</li> + * </ul> + * + * <p>If none of the above is found, returns {@code null}.</p> + * + * @param throwable the throwable to introspect for a cause, may be null + * @return the cause of the {@link Throwable}, + * {@code 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 {@link Throwable} to obtain the cause. + * + * <p>A {@code null} set of method names means use the default set. + * A {@code null} 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 {@link Throwable}, + * {@code 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; + } + return Stream.of(methodNames).map(m -> getCauseUsingMethodName(throwable, m)).filter(Objects::nonNull).findFirst().orElse(null); + } + + /** + * Gets a {@link 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 {@code null} if not found + */ + // TODO: Remove in Lang 4.0 + private static Throwable getCauseUsingMethodName(final Throwable throwable, final String methodName) { + if (methodName != null) { + Method method = null; + try { + method = throwable.getClass().getMethod(methodName); + } catch (final NoSuchMethodException | SecurityException ignored) { + // exception ignored + } + + if (method != null && Throwable.class.isAssignableFrom(method.getReturnType())) { + try { + return (Throwable) method.invoke(throwable); + } catch (final IllegalAccessException | IllegalArgumentException | InvocationTargetException ignored) { + // exception ignored + } + } + } + return null; + } + + /** + * Gets the default names used when searching for the cause of an exception. + * + * <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); + } + + /** + * Gets a short message summarizing the exception. + * <p> + * The message returned is of the form + * {ClassNameWithoutPackage}: {ThrowableMessage} + * </p> + * + * @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); + return clsName + ": " + StringUtils.defaultString(th.getMessage()); + } + + /** + * Introspects the {@link Throwable} to obtain the root cause. + * + * <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 {@link Throwable}, + * {@code null} if null throwable input + */ + public static Throwable getRootCause(final Throwable throwable) { + final List<Throwable> list = getThrowableList(throwable); + return list.isEmpty() ? null : list.get(list.size() - 1); + } + + /** + * Gets a short message summarizing the root cause exception. + * <p> + * The message returned is of the form + * {ClassNameWithoutPackage}: {ThrowableMessage} + * </p> + * + * @param throwable 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 throwable) { + final Throwable root = getRootCause(throwable); + return getMessage(root == null ? throwable : root); + } + + /** + * Gets a compact stack trace for the root cause of the supplied + * {@link Throwable}. + * + * <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) { + return getRootCauseStackTraceList(throwable).toArray(ArrayUtils.EMPTY_STRING_ARRAY); + } + + /** + * Gets a compact stack trace for the root cause of the supplied {@link Throwable}. + * + * <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 a list of stack trace frames, never null + * @since 3.13.0 + */ + public static List<String> getRootCauseStackTraceList(final Throwable throwable) { + if (throwable == null) { + return Collections.emptyList(); + } + 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; + } + + /** + * Gets a {@link List} of stack frames - the message + * is not included. Only the trace of the specified exception is + * returned, any caused by trace is stripped. + * + * <p>This works in most cases - it will only fail if the exception + * message contains a line that starts with: + * {@code " at".}</p> + * + * @param throwable is any throwable + * @return List of stack frames + */ + static List<String> getStackFrameList(final Throwable throwable) { + final String stackTrace = getStackTrace(throwable); + 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 != NOT_FOUND && token.substring(0, at).trim().isEmpty()) { + traceStarted = true; + list.add(token); + } else if (traceStarted) { + break; + } + } + return list; + } + + /** + * Gets an array where each element is a line from the argument. + * + * <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(ArrayUtils.EMPTY_STRING_ARRAY); + } + + /** + * Gets the stack trace associated with the specified + * {@link Throwable} object, decomposing it into a list of + * stack frames. + * + * <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 {@link 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)); + } + + /** + * Gets the stack trace from a Throwable as a String. + * + * <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 {@link Throwable} to be examined, may be null + * @return the stack trace as generated by the exception's + * {@code printStackTrace(PrintWriter)} method, or an empty String if {@code null} input + */ + public static String getStackTrace(final Throwable throwable) { + if (throwable == null) { + return StringUtils.EMPTY; + } + final StringWriter sw = new StringWriter(); + throwable.printStackTrace(new PrintWriter(sw, true)); + return sw.toString(); + } + + /** + * Gets a count of the number of {@link Throwable} objects in the + * exception chain. + * + * <p>A throwable without cause will return {@code 1}. + * A throwable with one cause will return {@code 2} and so on. + * A {@code null} throwable will return {@code 0}.</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(); + } + + /** + * Gets the list of {@link Throwable} objects in the + * exception chain. + * + * <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} 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 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; + } + + /** + * Performs an action for each Throwable causes of the given Throwable. + * <p> + * A throwable without cause will return a stream containing one element - the input throwable. A throwable with one cause + * will return a stream containing two elements. - the input throwable and the cause throwable. A {@code null} throwable + * will return a stream of count 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 traverse. + * @param consumer a non-interfering action to perform on the elements. + * @since 3.13.0 + */ + public static void forEach(final Throwable throwable, final Consumer<Throwable> consumer) { + stream(throwable).forEach(consumer); + } + + /** + * Gets the list of {@link Throwable} objects in the + * exception chain. + * + * <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} 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) { + return getThrowableList(throwable).toArray(ArrayUtils.EMPTY_THROWABLE_ARRAY); + } + + /** + * Tests if 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); + } + + /** + * Worker method for the {@code 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 {@code true}, compares with {@link Class#isAssignableFrom(Class)}, otherwise compares + * using references + * @return index of the {@code type} within throwables nested within the specified {@code throwable} + */ + private static int indexOf(final Throwable throwable, final Class<? extends Throwable> type, int fromIndex, final boolean subclass) { + if (throwable == null || type == null) { + return NOT_FOUND; + } + if (fromIndex < 0) { + fromIndex = 0; + } + final Throwable[] throwables = getThrowables(throwable); + if (fromIndex >= throwables.length) { + return NOT_FOUND; + } + 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 NOT_FOUND; + } + + /** + * Returns the (zero-based) index of the first {@link 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. + * + * <p>A {@code null} throwable returns {@code -1}. + * A {@code null} type returns {@code -1}. + * No match in the chain returns {@code -1}.</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<? extends Throwable> clazz) { + return indexOf(throwable, clazz, 0, false); + } + + /** + * Returns the (zero-based) index of the first {@link 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. + * + * <p>A {@code null} throwable returns {@code -1}. + * A {@code null} type returns {@code -1}. + * No match in the chain returns {@code -1}. + * A negative start index is treated as zero. + * A start index greater than the number of throwables returns {@code -1}.</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<? extends Throwable> clazz, final int fromIndex) { + return indexOf(throwable, clazz, fromIndex, false); + } + + /** + * Returns the (zero-based) index of the first {@link 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. + * + * <p>A {@code null} throwable returns {@code -1}. + * A {@code null} type returns {@code -1}. + * No match in the chain returns {@code -1}.</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<? extends Throwable> type) { + return indexOf(throwable, type, 0, true); + } + + /** + * Returns the (zero-based) index of the first {@link 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. + * + * <p>A {@code null} throwable returns {@code -1}. + * A {@code null} type returns {@code -1}. + * No match in the chain returns {@code -1}. + * A negative start index is treated as zero. + * A start index greater than the number of throwables returns {@code -1}.</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<? extends Throwable> type, final int fromIndex) { + return indexOf(throwable, type, fromIndex, true); + } + + /** + * Prints a compact stack trace for the root cause of a throwable + * to {@code System.err}. + * + * <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} 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. + * + * <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} for throwables + * that don't have nested causes.</p> + * + * @param throwable the throwable to output, may be null + * @param printStream the stream to output to, may not be null + * @throws NullPointerException if the printStream is {@code null} + * @since 2.0 + */ + @SuppressWarnings("resource") + public static void printRootCauseStackTrace(final Throwable throwable, final PrintStream printStream) { + if (throwable == null) { + return; + } + Objects.requireNonNull(printStream, "printStream"); + getRootCauseStackTraceList(throwable).forEach(printStream::println); + printStream.flush(); + } + + /** + * Prints a compact stack trace for the root cause of a throwable. + * + * <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} for throwables + * that don't have nested causes.</p> + * + * @param throwable the throwable to output, may be null + * @param printWriter the writer to output to, may not be null + * @throws NullPointerException if the printWriter is {@code null} + * @since 2.0 + */ + @SuppressWarnings("resource") + public static void printRootCauseStackTrace(final Throwable throwable, final PrintWriter printWriter) { + if (throwable == null) { + return; + } + Objects.requireNonNull(printWriter, "printWriter"); + getRootCauseStackTraceList(throwable).forEach(printWriter::println); + printWriter.flush(); + } + + /** + * 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 NullPointerException if either argument is null + * @since 2.0 + */ + public static void removeCommonFrames(final List<String> causeFrames, final List<String> wrapperFrames) { + Objects.requireNonNull(causeFrames, "causeFrames"); + Objects.requireNonNull(wrapperFrames, "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 + final String causeFrame = causeFrames.get(causeFrameIndex); + final String wrapperFrame = wrapperFrames.get(wrapperFrameIndex); + if (causeFrame.equals(wrapperFrame)) { + causeFrames.remove(causeFrameIndex); + } + causeFrameIndex--; + wrapperFrameIndex--; + } + } + + /** + * Throws 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. + * </p> + * <pre> + * 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 + * } + * } + * </pre> + * <p> + * This is an alternative to the more conservative approach of wrapping the + * checked exception in a RuntimeException: + * </p> + * <pre> + * 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 + * } + * } + * </pre> + * <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. + * </p> + * + * @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>eraseType(throwable); + } + + /** + * Streams causes of a Throwable. + * <p> + * A throwable without cause will return a stream containing one element - the input throwable. A throwable with one cause + * will return a stream containing two elements. - the input throwable and the cause throwable. A {@code null} throwable + * will return a stream of count 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 traverse + * @return A new Stream of Throwable causes. + * @since 3.13.0 + */ + public static Stream<Throwable> stream(final Throwable throwable) { + // No point building a custom Iterable as it would keep track of visited elements to avoid infinite loops + return getThrowableList(throwable).stream(); + } + + /** + * Worker method for the {@code throwableOfType} methods. + * + * @param <T> the type of Throwable you are searching. + * @param throwable the throwable to inspect, may be null + * @param type the type to search, subclasses match, null returns null + * @param fromIndex the (zero-based) index of the starting position, + * negative treated as zero, larger than chain size returns null + * @param subclass if {@code true}, compares with {@link Class#isAssignableFrom(Class)}, otherwise compares + * using references + * @return throwable of the {@code type} within throwables nested within the specified {@code throwable} + */ + private static <T extends Throwable> T throwableOf(final Throwable throwable, final Class<T> type, int fromIndex, final boolean subclass) { + if (throwable == null || type == null) { + return null; + } + if (fromIndex < 0) { + fromIndex = 0; + } + final Throwable[] throwables = getThrowables(throwable); + if (fromIndex >= throwables.length) { + return null; + } + if (subclass) { + for (int i = fromIndex; i < throwables.length; i++) { + if (type.isAssignableFrom(throwables[i].getClass())) { + return type.cast(throwables[i]); + } + } + } else { + for (int i = fromIndex; i < throwables.length; i++) { + if (type.equals(throwables[i].getClass())) { + return type.cast(throwables[i]); + } + } + } + return null; + } + + /** + * Returns the first {@link Throwable} + * that matches the specified class (exactly) in the exception chain. + * Subclasses of the specified class do not match - see + * {@link #throwableOfType(Throwable, Class)} for the opposite. + * + * <p>A {@code null} throwable returns {@code null}. + * A {@code null} type returns {@code null}. + * No match in the chain returns {@code null}.</p> + * + * @param <T> the type of Throwable you are searching. + * @param throwable the throwable to inspect, may be null + * @param clazz the class to search for, subclasses do not match, null returns null + * @return the first matching throwable from the throwable chain, null if no match or null input + * @since 3.10 + */ + public static <T extends Throwable> T throwableOfThrowable(final Throwable throwable, final Class<T> clazz) { + return throwableOf(throwable, clazz, 0, false); + } + + /** + * Returns the first {@link Throwable} + * that matches the specified type in the exception chain from + * a specified index. + * Subclasses of the specified class do not match - see + * {@link #throwableOfType(Throwable, Class, int)} for the opposite. + * + * <p>A {@code null} throwable returns {@code null}. + * A {@code null} type returns {@code null}. + * No match in the chain returns {@code null}. + * A negative start index is treated as zero. + * A start index greater than the number of throwables returns {@code null}.</p> + * + * @param <T> the type of Throwable you are searching. + * @param throwable the throwable to inspect, may be null + * @param clazz the class to search for, subclasses do not match, null returns null + * @param fromIndex the (zero-based) index of the starting position, + * negative treated as zero, larger than chain size returns null + * @return the first matching throwable from the throwable chain, null if no match or null input + * @since 3.10 + */ + public static <T extends Throwable> T throwableOfThrowable(final Throwable throwable, final Class<T> clazz, final int fromIndex) { + return throwableOf(throwable, clazz, fromIndex, false); + } + + /** + * Returns the throwable of the first {@link Throwable} + * that matches the specified class or subclass in the exception chain. + * Subclasses of the specified class do match - see + * {@link #throwableOfThrowable(Throwable, Class)} for the opposite. + * + * <p>A {@code null} throwable returns {@code null}. + * A {@code null} type returns {@code null}. + * No match in the chain returns {@code null}.</p> + * + * @param <T> the type of Throwable you are searching. + * @param throwable the throwable to inspect, may be null + * @param type the type to search for, subclasses match, null returns null + * @return the first matching throwable from the throwable chain, null if no match or null input + * @since 3.10 + */ + public static <T extends Throwable> T throwableOfType(final Throwable throwable, final Class<T> type) { + return throwableOf(throwable, type, 0, true); + } + + /** + * Returns the first {@link Throwable} + * that matches the specified type in the exception chain from + * a specified index. + * Subclasses of the specified class do match - see + * {@link #throwableOfThrowable(Throwable, Class)} for the opposite. + * + * <p>A {@code null} throwable returns {@code null}. + * A {@code null} type returns {@code null}. + * No match in the chain returns {@code null}. + * A negative start index is treated as zero. + * A start index greater than the number of throwables returns {@code null}.</p> + * + * @param <T> the type of Throwable you are searching. + * @param throwable the throwable to inspect, may be null + * @param type the type to search for, subclasses match, null returns null + * @param fromIndex the (zero-based) index of the starting position, + * negative treated as zero, larger than chain size returns null + * @return the first matching throwable from the throwable chain, null if no match or null input + * @since 3.10 + */ + public static <T extends Throwable> T throwableOfType(final Throwable throwable, final Class<T> type, final int fromIndex) { + return throwableOf(throwable, type, fromIndex, true); + } + + /** + * Throws 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. + * </p> + * + * @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); + } + + /** + * Public constructor allows an instance of {@link ExceptionUtils} to be created, although that is not + * normally necessary. + */ + public ExceptionUtils() { + } +} |