Github user StefanRRichter commented on a diff in the pull request:
https://github.com/apache/flink/pull/6196#discussion_r198114853
--- Diff:
flink-core/src/main/java/org/apache/flink/api/common/typeutils/CompositeSerializer.java
---
@@ -0,0 +1,204 @@
+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 java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+
+/**
+ * Base class for composite serializers.
+ *
+ * <p>This class serializes a list of objects
+ *
+ * @param <T> type of custom serialized value
+ */
+@SuppressWarnings("unchecked")
+public abstract class CompositeSerializer<T> extends TypeSerializer<T> {
--- End diff --
You could simply have tests for all the new serializer by extending
`SerializerTestBase`, which I would recommend to do to catch mistakes.
---
