com.hazelcast.cache.impl.DeferredValue Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2018, Hazelcast, Inc. All Rights Reserved.
*
* Licensed 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 com.hazelcast.cache.impl;
import com.hazelcast.nio.serialization.Data;
import com.hazelcast.spi.serialization.SerializationService;
import java.util.AbstractSet;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
/**
* Thread-safe holder of value and/or its serialized form.
*
* @param the type of value
*/
public final class DeferredValue {
private static final DeferredValue NULL_VALUE;
private volatile Data serializedValue;
private volatile V value;
private volatile boolean valueExists;
private volatile boolean serializedValueExists;
static {
DeferredValue nullValue = new DeferredValue();
nullValue.valueExists = true;
nullValue.serializedValueExists = true;
NULL_VALUE = nullValue;
}
private DeferredValue() {
}
// get-or-deserialize-and-get
public V get(SerializationService serializationService) {
if (!valueExists) {
// it's ok to deserialize twice in case of race
assert serializationService != null;
value = serializationService.toObject(serializedValue);
valueExists = true;
}
return value;
}
public Data getSerializedValue(SerializationService serializationService) {
if (!serializedValueExists) {
assert serializationService != null;
serializedValue = serializationService.toData(value);
serializedValueExists = true;
}
return serializedValue;
}
// returns a new DeferredValue representing the same value as this
public DeferredValue shallowCopy() {
if (this == NULL_VALUE) {
return NULL_VALUE;
}
DeferredValue copy = new DeferredValue();
if (serializedValueExists) {
copy.serializedValueExists = true;
copy.serializedValue = serializedValue;
}
if (valueExists) {
copy.valueExists = true;
copy.value = value;
}
return copy;
}
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
DeferredValue deferredValue = (DeferredValue) o;
if (valueExists && deferredValue.valueExists) {
return value != null ? value.equals(deferredValue.value) : deferredValue.value == null;
}
if (serializedValueExists && deferredValue.serializedValueExists) {
return serializedValue != null ? serializedValue.equals(deferredValue.serializedValue)
: deferredValue.serializedValue == null;
}
throw new IllegalArgumentException("Cannot compare serialized vs deserialized value");
}
@Override
public int hashCode() {
int result = serializedValue != null ? serializedValue.hashCode() : 0;
result = 31 * result + (value != null ? value.hashCode() : 0);
result = 31 * result + (valueExists ? 1 : 0);
result = 31 * result + (serializedValueExists ? 1 : 0);
return result;
}
public static DeferredValue withSerializedValue(Data serializedValue) {
if (serializedValue == null) {
return NULL_VALUE;
}
DeferredValue deferredValue = new DeferredValue();
deferredValue.serializedValue = serializedValue;
deferredValue.serializedValueExists = true;
return deferredValue;
}
public static DeferredValue withValue(V value) {
if (value == null) {
return NULL_VALUE;
}
DeferredValue deferredValue = new DeferredValue();
deferredValue.value = value;
deferredValue.valueExists = true;
return deferredValue;
}
@SuppressWarnings("unchecked")
public static DeferredValue withNullValue() {
return (DeferredValue) NULL_VALUE;
}
public static Set> concurrentSetOfValues(Set values) {
Set> result = Collections.newSetFromMap(new ConcurrentHashMap, Boolean>());
for (V value : values) {
result.add(DeferredValue.withValue(value));
}
return result;
}
/**
* Adapts a {@code Set>} as a {@code Set}. Operations on the returned set pass through to
* the original {@code deferredValues} set.
*
* @param deferredValues original set of deferred values to be adapted
* @param serializationService reference to {@link SerializationService}
* @param the value type
* @return a {@code Set} that wraps the {@code deferredValues} set.
*/
public static Set asPassThroughSet(Set> deferredValues, SerializationService serializationService) {
return new DeferredValueSet(serializationService, deferredValues);
}
private static class DeferredValueSet extends AbstractSet {
private final SerializationService serializationService;
private final Set> delegate;
public DeferredValueSet(SerializationService serializationService, Set> delegate) {
this.serializationService = serializationService;
this.delegate = delegate;
}
@Override
public int size() {
return delegate.size();
}
@Override
public Iterator iterator() {
return new DeferredValueIterator(serializationService, delegate.iterator());
}
public boolean add(V v) {
return delegate.add(DeferredValue.withValue(v));
}
@Override
public boolean remove(Object o) {
return delegate.remove(DeferredValue.withValue(o));
}
@Override
public void clear() {
delegate.clear();
}
private Collection> asDeferredValues(Collection collection) {
Collection> deferredValues = new ArrayList>();
for (Object object : collection) {
deferredValues.add(DeferredValue.withValue(object));
}
return deferredValues;
}
}
private static class DeferredValueIterator implements Iterator {
private final SerializationService serializationService;
private final Iterator> iterator;
public DeferredValueIterator(SerializationService serializationService, Iterator> iterator) {
this.serializationService = serializationService;
this.iterator = iterator;
}
@Override
public boolean hasNext() {
return iterator.hasNext();
}
@Override
public V next() {
DeferredValue next = iterator.next();
return next.get(serializationService);
}
@Override
public void remove() {
iterator.remove();
}
}
}