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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.spi;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import org.apache.logging.log4j.ThreadContext.ContextStack;
import org.apache.logging.log4j.util.StringBuilderFormattable;
import org.apache.logging.log4j.util.StringBuilders;
import org.apache.logging.log4j.util.Strings;
/**
* A copy-on-write thread-safe variant of {@code org.apache.logging.log4j.spi.ThreadContextStack} in which all mutative
* operations (add, pop, and so on) are implemented by making a fresh copy of the underlying list.
*/
public class DefaultThreadContextStack implements ThreadContextStack, StringBuilderFormattable {
private static final Object[] EMPTY_OBJECT_ARRAY = {};
private static final long serialVersionUID = 5050501L;
private static final ThreadLocal STACK = new ThreadLocal<>();
private final boolean useStack;
public DefaultThreadContextStack(final boolean useStack) {
this.useStack = useStack;
}
private MutableThreadContextStack getNonNullStackCopy() {
final MutableThreadContextStack values = STACK.get();
return (MutableThreadContextStack) (values == null ? new MutableThreadContextStack() : values.copy());
}
@Override
public boolean add(final String s) {
if (!useStack) {
return false;
}
final MutableThreadContextStack copy = getNonNullStackCopy();
copy.add(s);
copy.freeze();
STACK.set(copy);
return true;
}
@Override
public boolean addAll(final Collection strings) {
if (!useStack || strings.isEmpty()) {
return false;
}
final MutableThreadContextStack copy = getNonNullStackCopy();
copy.addAll(strings);
copy.freeze();
STACK.set(copy);
return true;
}
@Override
public List asList() {
final MutableThreadContextStack values = STACK.get();
if (values == null) {
return Collections.emptyList();
}
return values.asList();
}
@Override
public void clear() {
STACK.remove();
}
@Override
public boolean contains(final Object o) {
final MutableThreadContextStack values = STACK.get();
return values != null && values.contains(o);
}
@Override
public boolean containsAll(final Collection objects) {
if (objects.isEmpty()) { // quick check before accessing the ThreadLocal
return true; // looks counter-intuitive, but see
// j.u.AbstractCollection
}
final MutableThreadContextStack values = STACK.get();
return values != null && values.containsAll(objects);
}
@Override
public ThreadContextStack copy() {
MutableThreadContextStack values = null;
if (!useStack || (values = STACK.get()) == null) {
return new MutableThreadContextStack();
}
return values.copy();
}
@Override
public boolean equals(final Object obj) {
if (this == obj) {
return true;
}
if (obj == null) {
return false;
}
if (obj instanceof DefaultThreadContextStack) {
final DefaultThreadContextStack other = (DefaultThreadContextStack) obj;
if (this.useStack != other.useStack) {
return false;
}
}
if (!(obj instanceof ThreadContextStack)) {
return false;
}
final ThreadContextStack other = (ThreadContextStack) obj;
final MutableThreadContextStack values = STACK.get();
if (values == null) {
return false;
}
return values.equals(other);
}
@Override
public int getDepth() {
final MutableThreadContextStack values = STACK.get();
return values == null ? 0 : values.getDepth();
}
@Override
public int hashCode() {
final MutableThreadContextStack values = STACK.get();
final int prime = 31;
int result = 1;
// Factor in the stack itself to compare vs. other implementors.
result = prime * result + ((values == null) ? 0 : values.hashCode());
return result;
}
@Override
public boolean isEmpty() {
final MutableThreadContextStack values = STACK.get();
return values == null || values.isEmpty();
}
@Override
public Iterator iterator() {
final MutableThreadContextStack values = STACK.get();
if (values == null) {
final List empty = Collections.emptyList();
return empty.iterator();
}
return values.iterator();
}
@Override
public String peek() {
final MutableThreadContextStack values = STACK.get();
if (values == null || values.isEmpty()) {
return Strings.EMPTY;
}
return values.peek();
}
@Override
public String pop() {
if (!useStack) {
return Strings.EMPTY;
}
final MutableThreadContextStack values = STACK.get();
if (values == null || values.isEmpty()) {
// Like version 1.2
return Strings.EMPTY;
}
final MutableThreadContextStack copy = (MutableThreadContextStack) values.copy();
final String result = copy.pop();
copy.freeze();
STACK.set(copy);
return result;
}
@Override
public void push(final String message) {
if (!useStack) {
return;
}
add(message);
}
@Override
public boolean remove(final Object o) {
if (!useStack) {
return false;
}
final MutableThreadContextStack values = STACK.get();
if (values == null || values.isEmpty()) {
return false;
}
final MutableThreadContextStack copy = (MutableThreadContextStack) values.copy();
final boolean result = copy.remove(o);
copy.freeze();
STACK.set(copy);
return result;
}
@Override
public boolean removeAll(final Collection objects) {
if (!useStack || objects.isEmpty()) {
return false;
}
final MutableThreadContextStack values = STACK.get();
if (values == null || values.isEmpty()) {
return false;
}
final MutableThreadContextStack copy = (MutableThreadContextStack) values.copy();
final boolean result = copy.removeAll(objects);
copy.freeze();
STACK.set(copy);
return result;
}
@Override
public boolean retainAll(final Collection objects) {
if (!useStack || objects.isEmpty()) {
return false;
}
final MutableThreadContextStack values = STACK.get();
if (values == null || values.isEmpty()) {
return false;
}
final MutableThreadContextStack copy = (MutableThreadContextStack) values.copy();
final boolean result = copy.retainAll(objects);
copy.freeze();
STACK.set(copy);
return result;
}
@Override
public int size() {
final MutableThreadContextStack values = STACK.get();
return values == null ? 0 : values.size();
}
@Override
public Object[] toArray() {
final MutableThreadContextStack result = STACK.get();
if (result == null) {
return Strings.EMPTY_ARRAY;
}
return result.toArray(EMPTY_OBJECT_ARRAY);
}
@Override
public T[] toArray(final T[] ts) {
final MutableThreadContextStack result = STACK.get();
if (result == null) {
if (ts.length > 0) { // as per the contract of j.u.List#toArray(T[])
ts[0] = null;
}
return ts;
}
return result.toArray(ts);
}
@Override
public String toString() {
final MutableThreadContextStack values = STACK.get();
return values == null ? "[]" : values.toString();
}
@Override
public void formatTo(final StringBuilder buffer) {
final MutableThreadContextStack values = STACK.get();
if (values == null) {
buffer.append("[]");
} else {
StringBuilders.appendValue(buffer, values);
}
}
@Override
public void trim(final int depth) {
if (depth < 0) {
throw new IllegalArgumentException("Maximum stack depth cannot be negative");
}
final MutableThreadContextStack values = STACK.get();
if (values == null) {
return;
}
final MutableThreadContextStack copy = (MutableThreadContextStack) values.copy();
copy.trim(depth);
copy.freeze();
STACK.set(copy);
}
/*
* (non-Javadoc)
*
* @see org.apache.logging.log4j.ThreadContext.ContextStack#getImmutableStackOrNull()
*/
@Override
public ContextStack getImmutableStackOrNull() {
return STACK.get();
}
}