Retain target type hint when deserializing Stream records.

We now retain the target type when obtaining a HashMapper through StreamObjectMapper. To achieve this, we introduced the HashObjectReader interface accepting a target type.

Resolves: #2198
Related: #1566
Original Pull Request: #2253

src/test/java/org/springframework/data/redis/core/StreamObjectMapperUnitTests.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright 2022 the original author or authors.
+ *
+ * Licensed 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
+ *
+ *      https://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.springframework.data.redis.core;
+
+import static org.assertj.core.api.Assertions.*;
+
+import lombok.Data;
+
+import java.util.Collections;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.data.redis.hash.Jackson2HashMapper;
+import org.springframework.data.redis.hash.ObjectHashMapper;
+
+/**
+ * Unit tests for {@link StreamObjectMapper}.
+ *
+ * @author Mark Paluch
+ */
+class StreamObjectMapperUnitTests {
+
+	@Test // GH-2198
+	void shouldRetainTypeHintUsingObjectHashMapper() {
+
+		StreamObjectMapper mapper = new StreamObjectMapper(ObjectHashMapper.getSharedInstance());
+
+		MyType result = mapper.getHashMapper(MyType.class)
+				.fromHash(Collections.singletonMap("value".getBytes(), "hello".getBytes()));
+
+		assertThat(result.value).isEqualTo("hello");
+	}
+
+	@Test // GH-2198
+	void shouldRetainTypeHintUsingJackson() {
+
+		StreamObjectMapper mapper = new StreamObjectMapper(new Jackson2HashMapper(true));
+
+		MyType result = mapper.getHashMapper(MyType.class).fromHash(Collections.singletonMap("value", "hello"));
+
+		assertThat(result.value).isEqualTo("hello");
+	}
+
+	@Data
+	static class MyType {
+		String value;
+	}
+
+}

src/test/java/org/springframework/data/redis/mapping/Jackson2HashMapperUnitTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2021 the original author or authors.
+ * Copyright 2016-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -15,6 +15,8 @@
  */
 package org.springframework.data.redis.mapping;
 
+import static org.assertj.core.api.Assertions.*;
+
 import lombok.Data;
 
 import java.time.LocalDate;
@@ -48,13 +50,13 @@ public abstract class Jackson2HashMapperUnitTests extends AbstractHashMapperTest
 		this.mapper = mapper;
 	}
 
-	static class FlatteningJackson2HashMapperUnitTests extends Jackson2HashMapperUnitTests {
+	public static class FlatteningJackson2HashMapperUnitTests extends Jackson2HashMapperUnitTests {
 		FlatteningJackson2HashMapperUnitTests() {
 			super(new Jackson2HashMapper(true));
 		}
 	}
 
-	static class NonFlatteningJackson2HashMapperUnitTests extends Jackson2HashMapperUnitTests {
+	public static class NonFlatteningJackson2HashMapperUnitTests extends Jackson2HashMapperUnitTests {
 
 		NonFlatteningJackson2HashMapperUnitTests() {
 			super(new Jackson2HashMapper(false));
@@ -183,6 +185,24 @@ public abstract class Jackson2HashMapperUnitTests extends AbstractHashMapperTest
 		assertBackAndForwardMapping(source);
 	}
 
+	@Test // GH-2198
+	void shouldDeserializeObjectWithoutClassHint() {
+
+		WithDates source = new WithDates();
+		source.string = "id-1";
+		source.date = new Date(1561543964015L);
+		source.calendar = Calendar.getInstance();
+		source.localDate = LocalDate.parse("2018-01-02");
+		source.localDateTime = LocalDateTime.parse("2018-01-02T12:13:14");
+
+		Map<String, Object> map = mapper.toHash(source);
+
+		// ensure that we remove the correct type hint
+		assertThat(map.remove("@class")).isNotNull();
+
+		assertThat(mapper.fromHash(WithDates.class, map)).isEqualTo(source);
+	}
+
 	@Test // GH-1566
 	void mapFinalClass() {
 

src/test/java/org/springframework/data/redis/mapping/ObjectHashMapperTests.java

@@ -20,6 +20,7 @@ import static org.assertj.core.api.Assertions.*;
 import lombok.Data;
 
 import java.util.Collections;
+import java.util.LinkedHashMap;
 import java.util.Map;
 
 import org.junit.jupiter.api.Test;
@@ -83,6 +84,18 @@ class ObjectHashMapperTests extends AbstractHashMapperTests {
 		assertThat(objectHashMapper.fromHash(hash)).isEqualTo(source);
 	}
 
+	@Test // GH-2198
+	void readHashConsidersTypeHint() {
+
+		Map<byte[], byte[]> hash = new LinkedHashMap<>();
+		hash.put("value".getBytes(), "hello".getBytes());
+
+		ObjectHashMapper objectHashMapper = ObjectHashMapper.getSharedInstance();
+		WithTypeAlias withTypeAlias = objectHashMapper.fromHash(WithTypeAlias.class, hash);
+
+		assertThat(withTypeAlias.value).isEqualTo("hello");
+	}
+
 	@TypeAlias("_42_")
 	@Data
 	static class WithTypeAlias {