/*
* 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.util;
import java.lang.reflect.Method;
import java.util.Stack;
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.status.StatusLogger;
/**
* <em>Consider this class private.</em> Provides various methods to determine the caller class. <h3>Background</h3>
* <p>
* This method, available only in the Oracle/Sun/OpenJDK implementations of the Java Virtual Machine, is a much more
* efficient mechanism for determining the {@link Class} of the caller of a particular method. When it is not available,
* a {@link SecurityManager} is the second-best option. When this is also not possible, the {@code StackTraceElement[]}
* returned by {@link Throwable#getStackTrace()} must be used, and its {@code String} class name converted to a
* {@code Class} using the slow {@link Class#forName} (which can add an extra microsecond or more for each invocation
* depending on the runtime ClassLoader hierarchy).
* </p>
* <p>
* During Java 8 development, the {@code sun.reflect.Reflection.getCallerClass(int)} was removed from OpenJDK, and this
* change was back-ported to Java 7 in version 1.7.0_25 which changed the behavior of the call and caused it to be off
* by one stack frame. This turned out to be beneficial for the survival of this API as the change broke hundreds of
* libraries and frameworks relying on the API which brought much more attention to the intended API removal.
* </p>
* <p>
* After much community backlash, the JDK team agreed to restore {@code getCallerClass(int)} and keep its existing
* behavior for the rest of Java 7. However, the method is deprecated in Java 8, and current Java 9 development has not
* addressed this API. Therefore, the functionality of this class cannot be relied upon for all future versions of Java.
* It does, however, work just fine in Sun JDK 1.6, OpenJDK 1.6, Oracle/OpenJDK 1.7, and Oracle/OpenJDK 1.8. Other Java
* environments may fall back to using {@link Throwable#getStackTrace()} which is significantly slower due to
* examination of every virtual frame of execution.
* </p>
*/
public final class ReflectionStackLocator extends DefaultStackLocator {
// Checkstyle Suppress: the lower-case 'u' ticks off CheckStyle...
// CHECKSTYLE:OFF
static final int JDK_7u25_OFFSET;
// CHECKSTYLE:OFF
private static final boolean SUN_REFLECTION_SUPPORTED;
private static final Method GET_CALLER_CLASS;
private static final ReflectionStackLocator INSTANCE;
static {
Method getCallerClass;
int java7u25CompensationOffset = 0;
try {
final Class<?> sunReflectionClass = LoaderUtil.loadClass("sun.reflect.Reflection");
getCallerClass = sunReflectionClass.getDeclaredMethod("getCallerClass", int.class);
Object o = getCallerClass.invoke(null, 0);
final Object test1 = getCallerClass.invoke(null, 0);
if (o == null || o != sunReflectionClass) {
LOGGER.warn("Unexpected return value from Reflection.getCallerClass(): {}", test1);
getCallerClass = null;
java7u25CompensationOffset = -1;
} else {
o = getCallerClass.invoke(null, 1);
if (o == sunReflectionClass) {
LOGGER.warn("You are using Java 1.7.0_25 which has a broken implementation of "
+ "Reflection.getCallerClass.");
LOGGER.warn("You should upgrade to at least Java 1.7.0_40 or later.");
LOGGER.debug("Using stack depth compensation offset of 1 due to Java 7u25.");
java7u25CompensationOffset = 1;
}
}
} catch (final Exception | LinkageError e) {
LOGGER.info("sun.reflect.Reflection.getCallerClass is not supported. "
+ "ReflectionUtil.getCallerClass will be much slower due to this.", e);
getCallerClass = null;
java7u25CompensationOffset = -1;
}
SUN_REFLECTION_SUPPORTED = getCallerClass != null;
GET_CALLER_CLASS = getCallerClass;
JDK_7u25_OFFSET = java7u25CompensationOffset;
INSTANCE = new ReflectionStackLocator();
}
public static StackLocator getInstance() {
return INSTANCE;
}
private ReflectionStackLocator() {
}
// TODO: return Object.class instead of null (though it will have a null ClassLoader)
// (MS) I believe this would work without any modifications elsewhere, but I could be wrong
// migrated from ReflectiveCallerClassUtility
@PerformanceSensitive
public Class<?> getCallerClass(final int depth) {
if (depth < 0) {
throw new IndexOutOfBoundsException(Integer.toString(depth));
}
// note that we need to add 1 to the depth value to compensate for this method, but not for the Method.invoke
// since Reflection.getCallerClass ignores the call to Method.invoke()
try {
return (Class<?>) GET_CALLER_CLASS.invoke(null, depth + 1 + JDK_7u25_OFFSET);
} catch (final Exception e) {
// theoretically this could happen if the caller class were native code
LOGGER.error("Error in ReflectionUtil.getCallerClass({}).", depth, e);
// TODO: return Object.class
return null;
}
}
// migrated from Log4jLoggerFactory
@PerformanceSensitive
public Class<?> getCallerClass(final String fqcn, final String pkg) {
boolean next = false;
Class<?> clazz;
for (int i = 2; null != (clazz = getCallerClass(i)); i++) {
if (fqcn.equals(clazz.getName())) {
next = true;
continue;
}
if (next && clazz.getName().startsWith(pkg)) {
return clazz;
}
}
// TODO: return Object.class
return null;
}
// added for use in LoggerAdapter implementations mainly
@PerformanceSensitive
public Class<?> getCallerClass(final Class<?> anchor) {
boolean next = false;
Class<?> clazz;
for (int i = 2; null != (clazz = getCallerClass(i)); i++) {
if (anchor.equals(clazz)) {
next = true;
continue;
}
if (next) {
return clazz;
}
}
return Object.class;
}
// migrated from ThrowableProxy
@PerformanceSensitive
public Stack<Class<?>> getCurrentStackTrace() {
// benchmarks show that using the SecurityManager is much faster than looping through getCallerClass(int)
if (getSecurityManager() != null) {
final Class<?>[] array = getSecurityManager().getClassContext();
final Stack<Class<?>> classes = new Stack<>();
classes.ensureCapacity(array.length);
for (final Class<?> clazz : array) {
classes.push(clazz);
}
return classes;
}
// slower version using getCallerClass where we cannot use a SecurityManager
final Stack<Class<?>> classes = new Stack<>();
Class<?> clazz;
for (int i = 1; null != (clazz = getCallerClass(i)); i++) {
classes.push(clazz);
}
return classes;
}
}