[FLINK-8841] Remove HashMapSerializer and use MapSerializer instead.

This closes apache#5910.

flink-core/src/main/java/org/apache/flink/util/InstantiationUtil.java

@@ -21,6 +21,7 @@
 import org.apache.flink.annotation.Internal;
 import org.apache.flink.api.common.typeutils.TypeSerializer;
 import org.apache.flink.api.common.typeutils.TypeSerializerSerializationUtil;
+import org.apache.flink.api.common.typeutils.base.MapSerializer;
 import org.apache.flink.api.java.typeutils.runtime.KryoRegistrationSerializerConfigSnapshot;
 import org.apache.flink.configuration.Configuration;
 import org.apache.flink.core.io.IOReadableWritable;
@@ -41,8 +42,10 @@
 import java.io.Serializable;
 import java.lang.reflect.Constructor;
 import java.lang.reflect.Modifier;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
+import java.util.Map;
 import java.util.Set;
 
 /**
@@ -194,10 +197,12 @@ protected ObjectStreamClass readClassDescriptor() throws IOException, ClassNotFo
  try {
  Class.forName(streamClassDescriptor.getName(), false, classLoader);
  } catch (ClassNotFoundException e) {
- if (streamClassDescriptor.getName().equals("org.apache.avro.generic.GenericData$Array")) {
- ObjectStreamClass result = ObjectStreamClass.lookup(
- KryoRegistrationSerializerConfigSnapshot.DummyRegisteredClass.class);
- return result;
+
+ final ObjectStreamClass equivalentSerializer =
+ MigrationUtil.getEquivalentSerializer(streamClassDescriptor.getName());
+
+ if (equivalentSerializer != null) {
+ return equivalentSerializer;
  }
  }
 
@@ -221,6 +226,52 @@ protected ObjectStreamClass readClassDescriptor() throws IOException, ClassNotFo
  }
  }
 
+ /**
+ * A mapping between the full path of a deprecated serializer and its equivalent.
+ * These mappings are hardcoded and fixed.
+ *
+ * <p>IMPORTANT: mappings can be removed after 1 release as there will be a "migration path".
+ * As an example, a serializer is removed in 1.5-SNAPSHOT, then the mapping should be added for 1.5,
+ * and it can be removed in 1.6, as the path would be Flink-{< 1.5} -> Flink-1.5 -> Flink-{>= 1.6}.
+ */
+ private enum MigrationUtil {
+
+ // To add a new mapping just pick a name and add an entry as the following:
+
+ GENERIC_DATA_ARRAY_SERIALIZER(
+ "org.apache.avro.generic.GenericData$Array",
+ ObjectStreamClass.lookup(KryoRegistrationSerializerConfigSnapshot.DummyRegisteredClass.class)),
+ HASH_MAP_SERIALIZER(
+ "org.apache.flink.runtime.state.HashMapSerializer",
+ ObjectStreamClass.lookup(MapSerializer.class)); // added in 1.5
+
+ /** An internal unmodifiable map containing the mappings between deprecated and new serializers. */
+ private static final Map<String, ObjectStreamClass> EQUIVALENCE_MAP = Collections.unmodifiableMap(initMap());
+
+ /** The full name of the class of the old serializer. */
+ private final String oldSerializerName;
+
+ /** The serialization descriptor of the class of the new serializer. */
+ private final ObjectStreamClass newSerializerStreamClass;
+
+ MigrationUtil(String oldSerializerName, ObjectStreamClass newSerializerStreamClass) {
+ this.oldSerializerName = oldSerializerName;
+ this.newSerializerStreamClass = newSerializerStreamClass;
+ }
+
+ private static Map<String, ObjectStreamClass> initMap() {
+ final Map<String, ObjectStreamClass> init = new HashMap<>(4);
+ for (MigrationUtil m: MigrationUtil.values()) {
+ init.put(m.oldSerializerName, m.newSerializerStreamClass);
+ }
+ return init;
+ }
+
+ private static ObjectStreamClass getEquivalentSerializer(String classDescriptorName) {
+ return EQUIVALENCE_MAP.get(classDescriptorName);
+ }
+ }
+
  /**
  * Creates a new instance of the given class.
  *

flink-queryable-state/flink-queryable-state-runtime/src/test/java/org/apache/flink/queryablestate/network/KVStateRequestSerializerRocksDBTest.java

@@ -41,7 +41,6 @@
 import org.rocksdb.DBOptions;
 
 import java.io.File;
-import java.util.Map;
 
 import static org.mockito.Mockito.mock;
 
@@ -160,8 +159,8 @@ public void testMapSerialization() throws Exception {
  longHeapKeyedStateBackend.restore(null);
  longHeapKeyedStateBackend.setCurrentKey(key);
 
- final InternalMapState<Long, VoidNamespace, Long, String, Map<Long, String>> mapState =
- (InternalMapState<Long, VoidNamespace, Long, String, Map<Long, String>>)
+ final InternalMapState<Long, VoidNamespace, Long, String> mapState =
+ (InternalMapState<Long, VoidNamespace, Long, String>)
  longHeapKeyedStateBackend.getPartitionedState(
  VoidNamespace.INSTANCE,
  VoidNamespaceSerializer.INSTANCE,

flink-queryable-state/flink-queryable-state-runtime/src/test/java/org/apache/flink/queryablestate/network/KvStateRequestSerializerTest.java

@@ -307,8 +307,8 @@ public void testMapSerialization() throws Exception {
  );
  longHeapKeyedStateBackend.setCurrentKey(key);
 
- final InternalMapState<Long, VoidNamespace, Long, String, HashMap<Long, String>> mapState =
- (InternalMapState<Long, VoidNamespace, Long, String, HashMap<Long, String>>)
+ final InternalMapState<Long, VoidNamespace, Long, String> mapState =
+ (InternalMapState<Long, VoidNamespace, Long, String>)
  longHeapKeyedStateBackend.getPartitionedState(
  VoidNamespace.INSTANCE,
  VoidNamespaceSerializer.INSTANCE,
@@ -328,9 +328,9 @@ public void testMapSerialization() throws Exception {
  *
  * @throws Exception
  */
- public static <M extends Map<Long, String>> void testMapSerialization(
+ public static void testMapSerialization(
  final long key,
- final InternalMapState<Long, VoidNamespace, Long, String, M> mapState) throws Exception {
+ final InternalMapState<Long, VoidNamespace, Long, String> mapState) throws Exception {
 
  TypeSerializer<Long> userKeySerializer = LongSerializer.INSTANCE;
  TypeSerializer<String> userValueSerializer = StringSerializer.INSTANCE;

flink-runtime/src/main/java/org/apache/flink/runtime/state/AbstractKeyedStateBackend.java

@@ -53,7 +53,6 @@
 import java.io.IOException;
 import java.util.Collection;
 import java.util.HashMap;
-import java.util.Map;
 import java.util.stream.Stream;
 
 import static org.apache.flink.util.Preconditions.checkNotNull;
@@ -232,7 +231,7 @@ protected abstract <N, T, ACC> InternalFoldingState<K, N, T, ACC> createFoldingS
  * @param <UK> Type of the keys in the state
  * @param <UV> Type of the values in the state *
  */
- protected abstract <N, UK, UV> InternalMapState<K, N, UK, UV, ? extends Map<UK, UV>> createMapState(
+ protected abstract <N, UK, UV> InternalMapState<K, N, UK, UV> createMapState(
  TypeSerializer<N> namespaceSerializer,
  MapStateDescriptor<UK, UV> stateDesc) throws Exception;