/*
* 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.flink.api.common.typeutils.base;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.lang.reflect.Array;
import java.util.Arrays;
import java.util.HashMap;
import java.util.LinkedHashSet;
import java.util.Map;
import org.apache.flink.annotation.Internal;
import org.apache.flink.annotation.VisibleForTesting;
import org.apache.flink.api.common.typeutils.CompatibilityResult;
import org.apache.flink.api.common.typeutils.GenericTypeSerializerConfigSnapshot;
import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.api.common.typeutils.TypeSerializerConfigSnapshot;
import org.apache.flink.api.java.typeutils.runtime.DataInputViewStream;
import org.apache.flink.api.java.typeutils.runtime.DataOutputViewStream;
import org.apache.flink.core.memory.DataInputView;
import org.apache.flink.core.memory.DataOutputView;
import org.apache.flink.util.InstantiationUtil;
import org.apache.flink.util.Preconditions;
import static org.apache.flink.util.Preconditions.checkArgument;
import static org.apache.flink.util.Preconditions.checkNotNull;
@Internal
public final class EnumSerializer<T extends Enum<T>> extends TypeSerializer<T> {
private static final long serialVersionUID = 1L;
private final Class<T> enumClass;
/**
* Maintain our own map of enum value to their ordinal, instead of directly using {@link Enum#ordinal}.
* This allows us to maintain backwards compatibility for previous serialized data in the case that the
* order of enum constants was changed or new constants were added.
*
* <p>On a fresh start with no reconfiguration, the ordinals would simply be identical to the enum
* constants actual ordinals. Ordinals may change after reconfiguration.
*/
private Map<T, Integer> valueToOrdinal;
/**
* Array of enum constants with their indexes identical to their ordinals in the {@link #valueToOrdinal} map.
* Serves as a bidirectional map to have fast access from ordinal to value. May be reordered after reconfiguration.
*/
private T[] values;
public EnumSerializer(Class<T> enumClass) {
this.enumClass = checkNotNull(enumClass);
checkArgument(Enum.class.isAssignableFrom(enumClass), "not an enum");
this.values = enumClass.getEnumConstants();
checkArgument(this.values.length > 0, "cannot use an empty enum");
this.valueToOrdinal = new HashMap<>(values.length);
int i = 0;
for (T value : values) {
this.valueToOrdinal.put(value, i++);
}
}
@Override
public boolean isImmutableType() {
return true;
}
@Override
public EnumSerializer<T> duplicate() {
return this;
}
@Override
public T createInstance() {
return values[0];
}
@Override
public T copy(T from) {
return from;
}
@Override
public T copy(T from, T reuse) {
return from;
}
@Override
public int getLength() {
return 4;
}
@Override
public void serialize(T record, DataOutputView target) throws IOException {
// use our own maintained ordinals instead of the actual enum ordinal
target.writeInt(valueToOrdinal.get(record));
}
@Override
public T deserialize(DataInputView source) throws IOException {
return values[source.readInt()];
}
@Override
public T deserialize(T reuse, DataInputView source) throws IOException {
return values[source.readInt()];
}
@Override
public void copy(DataInputView source, DataOutputView target) throws IOException {
target.write(source, 4);
}
@Override
public boolean equals(Object obj) {
if(obj instanceof EnumSerializer) {
EnumSerializer<?> other = (EnumSerializer<?>) obj;
return other.canEqual(this) && other.enumClass == this.enumClass;
} else {
return false;
}
}
@Override
public boolean canEqual(Object obj) {
return obj instanceof EnumSerializer;
}
@Override
public int hashCode() {
return enumClass.hashCode();
}
// --------------------------------------------------------------------------------------------
private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
in.defaultReadObject();
// may be null if this serializer was deserialized from an older version
if (this.values == null) {
this.values = enumClass.getEnumConstants();
this.valueToOrdinal = new HashMap<>(values.length);
int i = 0;
for (T value : values) {
this.valueToOrdinal.put(value, i++);
}
}
}
// --------------------------------------------------------------------------------------------
// Serializer configuration snapshotting & compatibility
// --------------------------------------------------------------------------------------------
@Override
public EnumSerializerConfigSnapshot<T> snapshotConfiguration() {
return new EnumSerializerConfigSnapshot<>(enumClass, values);
}
@SuppressWarnings("unchecked")
@Override
public CompatibilityResult<T> ensureCompatibility(TypeSerializerConfigSnapshot configSnapshot) {
if (configSnapshot instanceof EnumSerializerConfigSnapshot) {
final EnumSerializerConfigSnapshot<T> config = (EnumSerializerConfigSnapshot<T>) configSnapshot;
if (enumClass.equals(config.getTypeClass())) {
// reorder enum constants so that previously existing constants
// remain in the same order, and new
LinkedHashSet<T> reorderedEnumConstants = new LinkedHashSet<>();
reorderedEnumConstants.addAll(Arrays.asList(config.getEnumConstants()));
reorderedEnumConstants.addAll(Arrays.asList(enumClass.getEnumConstants()));
// regenerate enum constant to ordinal bidirectional map
this.values = (T[]) Array.newInstance(enumClass, reorderedEnumConstants.size());
this.valueToOrdinal.clear();
int i = 0;
for (T constant : reorderedEnumConstants) {
this.values[i] = constant;
this.valueToOrdinal.put(constant, i);
i++;
}
return CompatibilityResult.compatible();
}
}
return CompatibilityResult.requiresMigration();
}
/**
* Configuration snapshot of a serializer for enumerations.
*
* Configuration contains the enum class, and an array of the enum's constants
* that existed when the configuration snapshot was taken.
*
* @param <T> the enum type.
*/
public static final class EnumSerializerConfigSnapshot<T extends Enum<T>>
extends GenericTypeSerializerConfigSnapshot<T> {
private static final int VERSION = 1;
private T[] enumConstants;
/** This empty nullary constructor is required for deserializing the configuration. */
public EnumSerializerConfigSnapshot() {}
public EnumSerializerConfigSnapshot(Class<T> enumClass, T[] enumConstants) {
super(enumClass);
this.enumConstants = Preconditions.checkNotNull(enumConstants);
}
@Override
public void write(DataOutputView out) throws IOException {
super.write(out);
try (final DataOutputViewStream outViewWrapper = new DataOutputViewStream(out)) {
InstantiationUtil.serializeObject(outViewWrapper, enumConstants);
}
}
@Override
public void read(DataInputView in) throws IOException {
super.read(in);
try (final DataInputViewStream inViewWrapper = new DataInputViewStream(in)) {
try {
enumConstants = InstantiationUtil.deserializeObject(inViewWrapper, getUserCodeClassLoader());
} catch (ClassNotFoundException e) {
throw new IOException("The requested enum class cannot be found in classpath.", e);
} catch (IllegalArgumentException e) {
throw new IOException("A previously existing enum constant of "
+ getTypeClass().getName() + " no longer exists.", e);
}
}
}
@Override
public int getVersion() {
return VERSION;
}
public T[] getEnumConstants() {
return enumConstants;
}
@Override
public boolean equals(Object obj) {
return super.equals(obj)
&& Arrays.equals(
enumConstants,
((EnumSerializerConfigSnapshot) obj).getEnumConstants());
}
@Override
public int hashCode() {
return super.hashCode() * 31 + Arrays.hashCode(enumConstants);
}
}
// --------------------------------------------------------------------------------------------
// Test utilities
// --------------------------------------------------------------------------------------------
@VisibleForTesting
T[] getValues() {
return values;
}
@VisibleForTesting
Map<T, Integer> getValueToOrdinal() {
return valueToOrdinal;
}
}