org.apache.logging.log4j.util.LazyUtil 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.util;
import java.lang.ref.WeakReference;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.function.Supplier;
final class LazyUtil {
private static final Object NULL = new Object() {
@Override
public String toString() {
return "null";
}
};
static Object wrapNull(final Object value) {
return value == null ? NULL : value;
}
static T unwrapNull(final Object value) {
return value == NULL ? null : Cast.cast(value);
}
static class Constant implements Lazy {
private final T value;
Constant(final T value) {
this.value = value;
}
@Override
public T value() {
return value;
}
@Override
public boolean isInitialized() {
return true;
}
@Override
public void set(final T newValue) {
throw new UnsupportedOperationException();
}
@Override
public String toString() {
return String.valueOf(value);
}
}
static class WeakConstant implements Lazy {
private final WeakReference reference;
WeakConstant(final T value) {
reference = new WeakReference<>(value);
}
@Override
public T value() {
return reference.get();
}
@Override
public boolean isInitialized() {
return true;
}
@Override
public void set(final T newValue) {
throw new UnsupportedOperationException();
}
@Override
public String toString() {
return String.valueOf(value());
}
}
static class SafeLazy implements Lazy {
private final Lock lock = new ReentrantLock();
private final Supplier supplier;
private volatile Object value;
SafeLazy(final Supplier supplier) {
this.supplier = supplier;
}
@Override
public T value() {
Object value = this.value;
if (value == null) {
lock.lock();
try {
value = this.value;
if (value == null) {
value = supplier.get();
this.value = wrapNull(value);
}
} finally {
lock.unlock();
}
}
return unwrapNull(value);
}
@Override
public void set(final T newValue) {
value = newValue;
}
public void reset() {
value = null;
}
@Override
public boolean isInitialized() {
return value != null;
}
@Override
public String toString() {
return isInitialized() ? String.valueOf(value) : "Lazy value not initialized";
}
}
static class PureLazy implements Lazy {
private final Supplier supplier;
private Object value;
public PureLazy(final Supplier supplier) {
this.supplier = supplier;
}
@Override
public T value() {
Object value = this.value;
if (value == null) {
value = supplier.get();
this.value = wrapNull(value);
}
return unwrapNull(value);
}
@Override
public boolean isInitialized() {
return value != null;
}
@Override
public void set(final T newValue) {
value = newValue;
}
}
}