DATACMNS-1762 - Extract NullableWrapperConverters from QueryExecutionConverters.

Nullable wrappers such as Java 8 Optional, Guava Optional, Scala Option and Vavr Option are now handled in NullableWrapperConverters and are no longer coupled to QueryExecutionConverters so that this functionality can be reused.

Original Pull Request: #459

Author: mp911de

src/main/java/org/springframework/data/repository/core/support/QueryExecutionResultHandler.java

@@ -27,9 +27,9 @@
 import org.springframework.core.convert.ConversionService;
 import org.springframework.core.convert.TypeDescriptor;
 import org.springframework.core.convert.support.GenericConversionService;
-import org.springframework.data.repository.util.NullableWrapper;
 import org.springframework.data.repository.util.QueryExecutionConverters;
 import org.springframework.data.repository.util.ReactiveWrapperConverters;
+import org.springframework.data.util.NullableWrapper;
 import org.springframework.data.util.Streamable;
 import org.springframework.lang.Nullable;
 

src/main/java/org/springframework/data/repository/util/NullableWrapper.java

@@ -23,41 +23,20 @@
  * convert {@literal null} into an object of some sort.
  *
  * @author Oliver Gierke
+ * @author Mark Paluch
  * @since 1.8
  * @see QueryExecutionConverters
+ * @deprecated since 2.4, use {@link org.springframework.data.util.NullableWrapper} instead.
  */
-public class NullableWrapper {
-
-	private final @Nullable Object value;
+@Deprecated
+public class NullableWrapper extends org.springframework.data.util.NullableWrapper {
 
 	/**
 	 * Creates a new {@link NullableWrapper} for the given value.
 	 *
 	 * @param value can be {@literal null}.
 	 */
 	public NullableWrapper(@Nullable Object value) {
-		this.value = value;
-	}
-
-	/**
-	 * Returns the type of the contained value. WIll fall back to {@link Object} in case the value is {@literal null}.
-	 *
-	 * @return will never be {@literal null}.
-	 */
-	public Class<?> getValueType() {
-
-		Object value = this.value;
-
-		return value == null ? Object.class : value.getClass();
-	}
-
-	/**
-	 * Returns the backing value.
-	 *
-	 * @return the value can be {@literal null}.
-	 */
-	@Nullable
-	public Object getValue() {
-		return value;
+		super(value);
 	}
 }