DATACMNS-1271 - Streamlined implementation of AnnotationBasedPersistentProperty to avoid NullPointerExceptions.

We now use the annotation cache's ….computeIfAbsent(…) to avoid inconsistencies between ….contains(…) and ….get(…) in multi-threaded scenarios.

src/main/java/org/springframework/data/util/StreamUtils.java

@@ -28,6 +28,7 @@ import java.util.stream.Collector;
 import java.util.stream.Stream;
 import java.util.stream.StreamSupport;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.MultiValueMap;
 
@@ -95,4 +96,15 @@ public interface StreamUtils {
 			Function<T, V> valueFunction) {
 		return MultiValueMapCollector.of(keyFunction, valueFunction);
 	}
+
+	/**
+	 * Creates a new {@link Stream} for the given value returning an empty {@link Stream} if the value is {@literal null}.
+	 * 
+	 * @param source can be {@literal null}.
+	 * @return a new {@link Stream} for the given value returning an empty {@link Stream} if the value is {@literal null}.
+	 * @since 2.0.6
+	 */
+	public static <T> Stream<T> fromNullable(@Nullable T source) {
+		return source == null ? Stream.empty() : Stream.of(source);
+	}
 }