org.apache.logging.log4j.util.StackLocator Maven / Gradle / Ivy
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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.logging.log4j.util;
import java.lang.reflect.Method;
import java.util.Stack;
/**
* Consider this class private. Provides various methods to determine the caller class. Background
*
* 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).
*
*
* 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.
*
*
* 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.
*
*/
public final class StackLocator {
// Checkstyle Suppress: the lower-case 'u' ticks off CheckStyle...
// CHECKSTYLE:OFF
static final int JDK_7u25_OFFSET;
// CHECKSTYLE:OFF
private static final Method GET_CALLER_CLASS;
private static final StackLocator 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);
getCallerClass.invoke(null, 0);
if (o == null || o != sunReflectionClass) {
getCallerClass = null;
java7u25CompensationOffset = -1;
} else {
o = getCallerClass.invoke(null, 1);
if (o == sunReflectionClass) {
System.out.println("WARNING: Java 1.7.0_25 is in use which has a broken implementation of Reflection.getCallerClass(). " +
" Please consider upgrading to Java 1.7.0_40 or later.");
java7u25CompensationOffset = 1;
}
}
} catch (final Exception | LinkageError e) {
System.out.println("WARNING: sun.reflect.Reflection.getCallerClass is not supported. This will impact performance.");
getCallerClass = null;
java7u25CompensationOffset = -1;
}
GET_CALLER_CLASS = getCallerClass;
JDK_7u25_OFFSET = java7u25CompensationOffset;
INSTANCE = new StackLocator();
}
public static StackLocator getInstance() {
return INSTANCE;
}
private StackLocator() {
}
// 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));
}
if (GET_CALLER_CLASS == null) {
return null;
}
// 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
// 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> getCurrentStackTrace() {
// benchmarks show that using the SecurityManager is much faster than looping through getCallerClass(int)
if (PrivateSecurityManagerStackTraceUtil.isEnabled()) {
return PrivateSecurityManagerStackTraceUtil.getCurrentStackTrace();
}
// slower version using getCallerClass where we cannot use a SecurityManager
final Stack> classes = new Stack<>();
Class clazz;
for (int i = 1; null != (clazz = getCallerClass(i)); i++) {
classes.push(clazz);
}
return classes;
}
public StackTraceElement calcLocation(final String fqcnOfLogger) {
if (fqcnOfLogger == null) {
return null;
}
// LOG4J2-1029 new Throwable().getStackTrace is faster than Thread.currentThread().getStackTrace().
final StackTraceElement[] stackTrace = new Throwable().getStackTrace();
boolean found = false;
for (int i = 0; i < stackTrace.length; i++) {
final String className = stackTrace[i].getClassName();
if (fqcnOfLogger.equals(className)) {
found = true;
continue;
}
if (found && !fqcnOfLogger.equals(className)) {
return stackTrace[i];
}
}
return null;
}
public StackTraceElement getStackTraceElement(final int depth) {
// (MS) I tested the difference between using Throwable.getStackTrace() and Thread.getStackTrace(), and
// the version using Throwable was surprisingly faster! at least on Java 1.8. See ReflectionBenchmark.
final StackTraceElement[] elements = new Throwable().getStackTrace();
int i = 0;
for (final StackTraceElement element : elements) {
if (isValid(element)) {
if (i == depth) {
return element;
}
++i;
}
}
throw new IndexOutOfBoundsException(Integer.toString(depth));
}
private boolean isValid(final StackTraceElement element) {
// ignore native methods (oftentimes are repeated frames)
if (element.isNativeMethod()) {
return false;
}
final String cn = element.getClassName();
// ignore OpenJDK internal classes involved with reflective invocation
if (cn.startsWith("sun.reflect.")) {
return false;
}
final String mn = element.getMethodName();
// ignore use of reflection including:
// Method.invoke
// InvocationHandler.invoke
// Constructor.newInstance
if (cn.startsWith("java.lang.reflect.") && (mn.equals("invoke") || mn.equals("newInstance"))) {
return false;
}
// ignore use of Java 1.9+ reflection classes
if (cn.startsWith("jdk.internal.reflect.")) {
return false;
}
// ignore Class.newInstance
if (cn.equals("java.lang.Class") && mn.equals("newInstance")) {
return false;
}
// ignore use of Java 1.7+ MethodHandle.invokeFoo() methods
if (cn.equals("java.lang.invoke.MethodHandle") && mn.startsWith("invoke")) {
return false;
}
// any others?
return true;
}
}