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StackLocator.java
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StackLocator.java
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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.util.ArrayDeque;
import java.util.Deque;
import java.util.function.Predicate;
/**
* <em>Consider this class private.</em> Determines the caller's class.
*/
public final class StackLocator {
private static final StackWalker WALKER = StackWalker.getInstance(StackWalker.Option.RETAIN_CLASS_REFERENCE);
private static final StackWalker STACK_WALKER = StackWalker.getInstance();
private static final StackLocator INSTANCE = new StackLocator();
public static StackLocator getInstance() {
return INSTANCE;
}
private StackLocator() {}
public Class<?> getCallerClass(final Class<?> sentinelClass, final Predicate<Class<?>> callerPredicate) {
if (sentinelClass == null) {
throw new IllegalArgumentException("sentinelClass cannot be null");
}
if (callerPredicate == null) {
throw new IllegalArgumentException("callerPredicate cannot be null");
}
return WALKER.walk(s -> s.map(StackWalker.StackFrame::getDeclaringClass)
// Skip until the sentinel class is found
.dropWhile(clazz -> !sentinelClass.equals(clazz))
// Skip until the predicate evaluates to true, also ignoring recurrences of the sentinel
.dropWhile(clazz -> sentinelClass.equals(clazz) || !callerPredicate.test(clazz))
.findFirst()
.orElse(null));
}
public Class<?> getCallerClass(final String fqcn) {
return getCallerClass(fqcn, "");
}
public Class<?> getCallerClass(final String fqcn, final String pkg) {
return WALKER.walk(s -> s.dropWhile(f -> !f.getClassName().equals(fqcn))
.dropWhile(f -> f.getClassName().equals(fqcn))
.dropWhile(f -> !f.getClassName().startsWith(pkg))
.findFirst())
.map(StackWalker.StackFrame::getDeclaringClass)
.orElse(null);
}
public Class<?> getCallerClass(final Class<?> anchor) {
return WALKER.walk(s -> s.dropWhile(f -> !f.getDeclaringClass().equals(anchor))
.dropWhile(f -> f.getDeclaringClass().equals(anchor))
.findFirst())
.map(StackWalker.StackFrame::getDeclaringClass)
.orElse(null);
}
public Class<?> getCallerClass(final int depth) {
return WALKER.walk(s -> s.skip(depth).findFirst())
.map(StackWalker.StackFrame::getDeclaringClass)
.orElse(null);
}
public Deque<Class<?>> getCurrentStackTrace() {
// benchmarks show that using the SecurityManager is much faster than looping through getCallerClass(int)
if (PrivateSecurityManagerStackTraceUtil.isEnabled()) {
return PrivateSecurityManagerStackTraceUtil.getCurrentStackTrace();
}
final Deque<Class<?>> stack = new ArrayDeque<Class<?>>();
return WALKER.walk(s -> {
s.forEach(f -> stack.add(f.getDeclaringClass()));
return stack;
});
}
public StackTraceElement calcLocation(final String fqcnOfLogger) {
return STACK_WALKER
.walk(s -> s.dropWhile(f ->
!f.getClassName().equals(fqcnOfLogger)) // drop the top frames until we reach the logger
.dropWhile(f -> f.getClassName().equals(fqcnOfLogger)) // drop the logger frames
.findFirst())
.map(StackWalker.StackFrame::toStackTraceElement)
.orElse(null);
}
public StackTraceElement getStackTraceElement(final int depth) {
return STACK_WALKER
.walk(s -> s.skip(depth).findFirst())
.map(StackWalker.StackFrame::toStackTraceElement)
.orElse(null);
}
}