Github user StefanRRichter commented on a diff in the pull request:
https://github.com/apache/flink/pull/6196#discussion_r199474421
--- Diff:
flink-core/src/main/java/org/apache/flink/api/common/typeutils/CompositeSerializer.java
---
@@ -0,0 +1,258 @@
+/*
+ * 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;
+
+import org.apache.flink.api.java.tuple.Tuple2;
+import org.apache.flink.core.memory.DataInputView;
+import org.apache.flink.core.memory.DataOutputView;
+import org.apache.flink.util.Preconditions;
+
+import javax.annotation.Nonnull;
+
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Objects;
+
+/**
+ * Base class for composite serializers.
+ *
+ * <p>This class serializes a composite type using array of its field
serializers.
+ * Fields are indexed the same way as their serializers.
+ *
+ * @param <T> type of custom serialized value
+ */
+public abstract class CompositeSerializer<T> extends TypeSerializer<T> {
+ private static final long serialVersionUID = 1L;
+
+ protected final TypeSerializer<Object>[] fieldSerializers;
+ final boolean isImmutableTargetType;
+ private final int length;
+
+ @SuppressWarnings("unchecked")
+ protected CompositeSerializer(boolean isImmutableTargetType,
TypeSerializer<?> ... fieldSerializers) {
+ Preconditions.checkNotNull(fieldSerializers);
+
Preconditions.checkArgument(Arrays.stream(fieldSerializers).allMatch(Objects::nonNull));
+ this.isImmutableTargetType = isImmutableTargetType;
+ this.fieldSerializers = (TypeSerializer<Object>[])
fieldSerializers;
+ this.length = calcLength();
+ }
+
+ /** Create new instance from its fields. */
+ public abstract T createInstance(@Nonnull Object ... values);
+
+ /** Modify field of existing instance. Supported only by mutable types.
*/
+ protected abstract void setField(@Nonnull T value, int index, Object
fieldValue);
+
+ /** Get field of existing instance. */
+ protected abstract Object getField(@Nonnull T value, int index);
+
+ /** Factory for concrete serializer. */
+ protected abstract CompositeSerializer<T>
createSerializerInstance(TypeSerializer<?> ... originalSerializers);
+
+ @Override
+ public CompositeSerializer<T> duplicate() {
+ TypeSerializer[] duplicatedSerializers = new
TypeSerializer[fieldSerializers.length];
+ boolean stateful = false;
+ for (int index = 0; index < fieldSerializers.length; index++) {
+ duplicatedSerializers[index] =
fieldSerializers[index].duplicate();
+ if (fieldSerializers[index] !=
duplicatedSerializers[index]) {
+ stateful = true;
+ }
+ }
+ return stateful ?
createSerializerInstance(duplicatedSerializers) : this;
+ }
+
+ @Override
+ public boolean isImmutableType() {
+ for (TypeSerializer<Object> fieldSerializer : fieldSerializers)
{
+ if (!fieldSerializer.isImmutableType()) {
+ return false;
+ }
+ }
+ return isImmutableTargetType;
+ }
+
+ @Override
+ public T createInstance() {
+ Object[] fields = new Object[fieldSerializers.length];
+ for (int index = 0; index < fieldSerializers.length; index++) {
+ fields[index] =
fieldSerializers[index].createInstance();
+ }
+ return createInstance(fields);
+ }
+
+ @Override
+ public T copy(T from) {
+ Preconditions.checkNotNull(from);
+ Object[] fields = new Object[fieldSerializers.length];
+ for (int index = 0; index < fieldSerializers.length; index++) {
+ fields[index] =
fieldSerializers[index].copy(getField(from, index));
+ }
+ return createInstance(fields);
--- End diff --
This method can return `from` if `isImmutableType()`
---
