org.apache.logging.log4j.core.util.Throwables Maven / Gradle / Ivy
/*
* 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.logging.log4j.core.util;
import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
import java.io.IOException;
import java.io.InterruptedIOException;
import java.io.LineNumberReader;
import java.io.PrintWriter;
import java.io.StringReader;
import java.io.StringWriter;
import java.util.ArrayList;
import java.util.List;
/**
* Helps with Throwable objects.
*/
public final class Throwables {
private Throwables() {}
/**
* Returns the deepest cause of the given {@code throwable}.
*
* @param throwable the throwable to navigate
* @return the deepest throwable or the given throwable
*/
public static Throwable getRootCause(final Throwable throwable) {
// Keep a second pointer that slowly walks the causal chain. If the fast
// pointer ever catches the slower pointer, then there's a loop.
Throwable slowPointer = throwable;
boolean advanceSlowPointer = false;
Throwable parent = throwable;
Throwable cause;
while ((cause = parent.getCause()) != null) {
parent = cause;
if (parent == slowPointer) {
throw new IllegalArgumentException("loop in causal chain");
}
if (advanceSlowPointer) {
slowPointer = slowPointer.getCause();
}
advanceSlowPointer = !advanceSlowPointer; // only advance every other iteration
}
return parent;
}
/**
* Converts a Throwable stack trace into a List of Strings.
*
* @param throwable the Throwable
* @return a List of Strings
*/
@SuppressFBWarnings(
value = "INFORMATION_EXPOSURE_THROUGH_AN_ERROR_MESSAGE",
justification = "Log4j prints stacktraces only to logs, which should be private.")
public static List toStringList(final Throwable throwable) {
final StringWriter sw = new StringWriter();
final PrintWriter pw = new PrintWriter(sw);
try {
throwable.printStackTrace(pw);
} catch (final RuntimeException ex) {
// Ignore any exceptions.
}
pw.flush();
final List lines = new ArrayList<>();
final LineNumberReader reader = new LineNumberReader(new StringReader(sw.toString()));
try {
String line = reader.readLine();
while (line != null) {
lines.add(line);
line = reader.readLine();
}
} catch (final IOException ex) {
if (ex instanceof InterruptedIOException) {
Thread.currentThread().interrupt();
}
lines.add(ex.toString());
} finally {
Closer.closeSilently(reader);
}
return lines;
}
/**
* Rethrows a {@link Throwable}.
*
* @param t the Throwable to throw.
* @since 2.1
*/
public static void rethrow(final Throwable t) {
Throwables.rethrow0(t);
}
@SuppressWarnings("unchecked")
private static void rethrow0(final Throwable t) throws T {
throw (T) t;
}
}