Improve EnumSet handling in MappingRedisConverter.

Add special handling of EnumSet, extracting the value type hint from the source to create the instance. See: spring-projects#3179

Author: christophstrobl

src/main/java/org/springframework/data/redis/core/convert/MappingRedisConverter.java

@@ -409,10 +409,15 @@ public void write(@Nullable Object source, RedisData sink) {
 if (collection instanceof List) {
 collectionTargetType = List.class;
 } else if (collection instanceof Set) {
-collectionTargetType = collection instanceof EnumSet ? EnumSet.class : Set.class;
+if (collection instanceof EnumSet<?>) {
+collectionTargetType = EnumSet.class;
+} else {
+collectionTargetType = Set.class;
+}
 }
+
 typeMapper.writeType(collectionTargetType, sink.getBucket().getPath());
-writeCollection(sink.getKeyspace(), "", collection, TypeInformation.of(Object.class), sink);
+writeCollection(sink.getKeyspace(), "", collection, TypeInformation.OBJECT, sink);
 return;
 }
 
@@ -829,7 +834,13 @@ private void writeToBucket(String path, @Nullable Object value, RedisData sink,
 
 boolean isArray = collectionType.isArray();
 Class<?> collectionTypeToUse = isArray ? ArrayList.class : collectionType;
-Collection<Object> target = CollectionFactory.createCollection(collectionTypeToUse, valueType, keys.size());
+Class<?> valueTypeToUse = valueType;
+
+if (collectionTypeToUse == EnumSet.class) {
+valueTypeToUse = findFirstElementType(bucket, keys, valueType);
+}
+
+Collection<Object> target = CollectionFactory.createCollection(collectionTypeToUse, valueTypeToUse, keys.size());
 
 for (String key : keys) {
 
@@ -977,6 +988,17 @@ private void writeMap(@Nullable String keyspace, String path, Class<?> mapValueT
 return conversionService.convert(toBytes(mapKey), targetType);
 }
 
+private Class<?> findFirstElementType(Bucket bucket, List<String> keys, Class<?> fallbackType) {
+
+Optional<String> firstElement = keys.stream().filter(typeMapper::isTypeKey)
+.map(it -> it.substring(0, it.indexOf(']') + 1)).findFirst();
+if (firstElement.isEmpty()) {
+return fallbackType;
+}
+
+return getTypeHint(firstElement.get(), bucket, fallbackType);
+}
+
 private Class<?> getTypeHint(String path, Bucket bucket, Class<?> fallback) {
 
 TypeInformation<?> typeInformation = typeMapper.readType(bucket.getPropertyPath(path),

src/test/java/org/springframework/data/redis/core/convert/MappingRedisConverterUnitTests.java

@@ -59,6 +59,7 @@
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Date;
+import java.util.EnumSet;
 import java.util.HashMap;
 import java.util.LinkedHashMap;
 import java.util.List;
@@ -2044,11 +2045,14 @@ void readsPlainCollectionIfObjectTypeRequested(Class<?> type, Collection<Object>
 
 Object target = this.converter.read(Object.class, source.getRedisData());
 
-assertThat(target).isInstanceOf(type).asInstanceOf(InstanceOfAssertFactories.COLLECTION).containsExactlyElementsOf(collection);
+assertThat(target).isInstanceOf(type).asInstanceOf(InstanceOfAssertFactories.COLLECTION)
+.containsExactlyElementsOf(collection);
 }
 
 private static Stream<Arguments> justCollections() {
-return Stream.of(Arguments.of(List.class, Arrays.asList("Hello", "stream", "message", 100L)), Arguments.of(Set.class, Set.of("Hello", "stream", "message", 100L)));
+return Stream.of(Arguments.of(List.class, Arrays.asList("Hello", "stream", "message", 100L)),
+Arguments.of(Set.class, Set.of("Hello", "stream", "message", 100L)),
+Arguments.of(EnumSet.class, EnumSet.allOf(Gender.class)));
 }
 
 private RedisTestData write(Object source) {