Update nullability annotations for Jackson based HashMapper.

See: #3154

Author: christophstrobl

src/main/java/org/springframework/data/redis/hash/FlatEric.java

@@ -26,6 +26,7 @@
 import java.util.Set;
 import java.util.function.BiConsumer;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.util.CollectionUtils;
 import org.springframework.util.StringUtils;
 
@@ -380,7 +381,7 @@ public interface JsonNodeAdapter {
 
 		Collection<Map.Entry<String, JsonNodeAdapter>> properties();
 
-		Object getDirectValue();
+		@Nullable Object getDirectValue();
 	}
 
 }

src/main/java/org/springframework/data/redis/hash/Jackson2HashMapper.java

@@ -478,7 +478,7 @@ public Collection<Entry<String, FlatEric.JsonNodeAdapter>> properties() {
 		}
 
 		@Override
-		public Object getDirectValue() {
+		public @Nullable Object getDirectValue() {
 			return new DirectFieldAccessFallbackBeanWrapper(node()).getPropertyValue("_value");
 		}
 

src/main/java/org/springframework/data/redis/hash/Jackson3HashMapper.java

@@ -655,7 +655,7 @@ public Collection<Entry<String, FlatEric.JsonNodeAdapter>> properties() {
 		}
 
 		@Override
-		public Object getDirectValue() {
+		public @Nullable Object getDirectValue() {
 			return new DirectFieldAccessFallbackBeanWrapper(node()).getPropertyValue("_value");
 		}