hazelcast-master/hazelcast/src/main/java/com/hazelcast/map/impl/LazyMapEntry.java
/*
 * Copyright (c) 2008-2023, 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.map.impl;

import com.hazelcast.config.InMemoryFormat;
import com.hazelcast.internal.serialization.Data;
import com.hazelcast.internal.serialization.InternalSerializationService;
import com.hazelcast.map.ExtendedMapEntry;
import com.hazelcast.nio.ObjectDataInput;
import com.hazelcast.nio.ObjectDataOutput;
import com.hazelcast.nio.serialization.IdentifiedDataSerializable;
import com.hazelcast.query.impl.CachedQueryEntry;
import com.hazelcast.query.impl.getters.Extractors;

import java.io.IOException;
import java.io.Serializable;
import java.util.Map;
import java.util.Objects;
import java.util.concurrent.TimeUnit;

import static com.hazelcast.map.impl.record.Record.UNSET;

/**
 * A {@link java.util.Map.Entry Map.Entry} implementation
 * which serializes/de-serializes key and value objects on
 * demand. It is beneficial when you need to prevent unneeded
 * serialization/de-serialization when creating a {@link
 * java.util.Map.Entry Map.Entry}. Mainly targeted to supply a lazy entry
 * to {@link com.hazelcast.map.EntryProcessor#process(Map.Entry)} method.
 * <p>
 * <STRONG>
 * Note that this implementation is not
 * synchronized and is not thread-safe.
 * </STRONG>
 * <p>
 * LazyMapEntry itself is serializable as long as the object
 * representations of both key and value are serializable.
 * After serialization objects are resolved using injected
 * SerializationService. De-serialized LazyMapEntry does
 * contain object representation only Data representations
 * and SerializationService is set to null. In other
 * words: It's as usable just as a regular Map.Entry.
 *
 * @param <K> key
 * @param <V> value
 */
public class LazyMapEntry<K, V> extends CachedQueryEntry<K, V>
        implements Serializable, IdentifiedDataSerializable, ExtendedMapEntry<K, V> {

    private static final long serialVersionUID = 0L;

    private transient long newTtl = UNSET;
    private transient boolean modified;
    private transient boolean changeExpiryOnUpdate = true;

    public LazyMapEntry() {
    }

    public LazyMapEntry(Object key, Object value, InternalSerializationService serializationService) {
        this(key, value, serializationService, null);
    }

    public LazyMapEntry(Object key, Object value, InternalSerializationService serializationService, Extractors extractors) {
        init(serializationService, key, value, extractors);
    }

    public LazyMapEntry init(InternalSerializationService serializationService,
                             Object key, Object value, Extractors extractors, long ttl,
                             boolean changeExpiryOnUpdate) {
        super.init(serializationService, key, value, extractors);
        this.modified = false;
        this.newTtl = ttl;
        this.changeExpiryOnUpdate = changeExpiryOnUpdate;
        return this;
    }

    public void setValueByInMemoryFormat(InMemoryFormat inMemoryFormat, Object value) {
        if (inMemoryFormat == InMemoryFormat.OBJECT) {
            valueObject = (V) value;
            valueData = null;
        } else {
            valueData = (Data) value;
            valueObject = null;
        }
    }

    @Override
    public V setValue(V value) {
        modified = true;
        V oldValue = getValue();
        this.valueObject = value;
        this.valueData = null;
        this.changeExpiryOnUpdate = true;
        this.newTtl = UNSET;
        return oldValue;
    }

    @Override
    public V setValue(V value, long ttl, TimeUnit ttlUnit) {
        V v = setValue(value);
        newTtl = ttlUnit.toMillis(ttl);
        return v;
    }

    @Override
    public V setValueWithoutChangingExpiryTime(V value) {
        V v = setValue(value);
        changeExpiryOnUpdate = false;
        return v;
    }

    /**
     * Similar to calling {@link #setValue} with null but doesn't return old-value hence no extra deserialization.
     */
    public void remove() {
        modified = true;
        valueObject = null;
        valueData = null;
    }

    /**
     * Checks if this entry has null value without any deserialization.
     *
     * @return true if value is null, otherwise returns false.
     */
    public boolean hasNullValue() {
        return valueObject == null && valueData == null;
    }

    public boolean isModified() {
        return modified;
    }

    public long getNewTtl() {
        return newTtl;
    }

    public boolean isChangeExpiryOnUpdate() {
        return changeExpiryOnUpdate;
    }

    @Override
    public boolean equals(Object o) {
        if (!(o instanceof Map.Entry)) {
            return false;
        }
        Map.Entry<?, ?> e = (Map.Entry<?, ?>) o;
        return Objects.equals(getKey(), e.getKey())
                && Objects.equals(getValue(), e.getValue());
    }

    @Override
    public int hashCode() {
        return (getKey() == null ? 0 : getKey().hashCode())
                ^ (getValue() == null ? 0 : getValue().hashCode());
    }

    @Override
    public String toString() {
        return getKey() + "=" + getValue();
    }

    @SuppressWarnings("unchecked")
    private void readObject(java.io.ObjectInputStream in) throws IOException, ClassNotFoundException {
        in.defaultReadObject();
        keyObject = (K) in.readObject();
        valueObject = (V) in.readObject();
    }

    private void writeObject(java.io.ObjectOutputStream out) throws IOException {
        out.defaultWriteObject();
        out.writeObject(getKey());
        out.writeObject(getValue());
    }

    @Override
    public void readData(ObjectDataInput in) throws IOException {
        keyObject = in.readObject();
        valueObject = in.readObject();
    }

    @Override
    public void writeData(ObjectDataOutput out) throws IOException {
        out.writeObject(getKey());
        out.writeObject(getValue());
    }

    @Override
    public int getFactoryId() {
        return MapDataSerializerHook.F_ID;
    }

    @Override
    public int getClassId() {
        return MapDataSerializerHook.LAZY_MAP_ENTRY;
    }
}
