[flink] 01/02: [FLINK-11323] Add a generic type snapshot base

[al...@apache.org]

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aljoscha pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/flink.git

commit 9268c0520a2d4b3e0a4aafeccc55568dcc407575
Author: Igal Shilman <ig...@data-artisans.com>
AuthorDate: Sat Feb 9 21:08:38 2019 +0100

    [FLINK-11323] Add a generic type snapshot base
---
 .../typeutils/GenericTypeSerializerSnapshot.java   | 100 +++++++++++++++++++++
 1 file changed, 100 insertions(+)

diff --git a/flink-core/src/main/java/org/apache/flink/api/common/typeutils/GenericTypeSerializerSnapshot.java b/flink-core/src/main/java/org/apache/flink/api/common/typeutils/GenericTypeSerializerSnapshot.java
new file mode 100644
index 0000000..5e8b22a
--- /dev/null
+++ b/flink-core/src/main/java/org/apache/flink/api/common/typeutils/GenericTypeSerializerSnapshot.java
@@ -0,0 +1,100 @@
+/*
+ * 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.annotation.Internal;
+import org.apache.flink.core.memory.DataInputView;
+import org.apache.flink.core.memory.DataOutputView;
+import org.apache.flink.util.InstantiationUtil;
+
+import java.io.IOException;
+
+import static org.apache.flink.util.Preconditions.checkNotNull;
+import static org.apache.flink.util.Preconditions.checkState;
+
+/**
+ * Base {@link TypeSerializerSnapshot} for serializers for generic types.
+ *
+ * @param <T> The type to be instantiated.
+ */
+@Internal
+public abstract class GenericTypeSerializerSnapshot<T, S extends TypeSerializer> implements TypeSerializerSnapshot<T> {
+
+	private static final int VERSION = 2;
+	private Class<T> typeClass;
+
+	protected GenericTypeSerializerSnapshot() {
+	}
+
+	protected GenericTypeSerializerSnapshot(Class<T> typeClass) {
+		this.typeClass = checkNotNull(typeClass, "type class can not be NULL");
+	}
+
+	/**
+	 * Create a serializer that is able to serialize the generic type {@code typeClass}.
+	 */
+	protected abstract TypeSerializer<T> createSerializer(Class<T> typeClass);
+
+	/**
+	 * Gets the type class from the corresponding serializer.
+	 */
+	protected abstract Class<T> getTypeClass(S serializer);
+
+	/**
+	 * Gets the serializer's class.
+	 */
+	protected abstract Class<?> serializerClass();
+
+	@Override
+	public final int getCurrentVersion() {
+		return VERSION;
+	}
+
+	@Override
+	public final void writeSnapshot(DataOutputView out) throws IOException {
+		checkState(typeClass != null, "type class can not be NULL");
+		out.writeUTF(typeClass.getName());
+	}
+
+	@Override
+	public final void readSnapshot(int readVersion, DataInputView in, ClassLoader userCodeClassLoader) throws IOException {
+		typeClass = InstantiationUtil.resolveClassByName(in, userCodeClassLoader);
+	}
+
+	@Override
+	@SuppressWarnings("unchecked")
+	public final TypeSerializer<T> restoreSerializer() {
+		checkState(typeClass != null, "type class can not be NULL");
+		return createSerializer(typeClass);
+	}
+
+	@Override
+	public final TypeSerializerSchemaCompatibility<T> resolveSchemaCompatibility(TypeSerializer<T> newSerializer) {
+		if (!serializerClass().isInstance(newSerializer)) {
+			return TypeSerializerSchemaCompatibility.incompatible();
+		}
+		@SuppressWarnings("unchecked") S casted = (S) newSerializer;
+		if (typeClass == getTypeClass(casted)) {
+			return TypeSerializerSchemaCompatibility.compatibleAsIs();
+		}
+		else {
+			return TypeSerializerSchemaCompatibility.incompatible();
+		}
+	}
+}