Polish "Bind Optional value object parameters as empty rather than null"

See gh-49152

Author: philwebb

core/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/BindConverter.java

@@ -98,16 +98,8 @@ private boolean canConvert(@Nullable TypeDescriptor sourceType, TypeDescriptor t
 
 	@SuppressWarnings("unchecked")
 	<T> @Nullable T convert(@Nullable Object source, ResolvableType targetType, Annotation... targetAnnotations) {
-		if (source == null) {
-			return null;
-		}
-		return (T) convert(source, TypeDescriptor.forObject(source),
-				new ResolvableTypeDescriptor(targetType, targetAnnotations));
-	}
-
-	@SuppressWarnings("unchecked")
-	<T> @Nullable T convertNullValue(ResolvableType targetType, Annotation... targetAnnotations) {
-		return (T) convert(null, null, new ResolvableTypeDescriptor(targetType, targetAnnotations));
+		TypeDescriptor sourceType = (source != null) ? TypeDescriptor.forObject(source) : null;
+		return (T) convert(source, sourceType, new ResolvableTypeDescriptor(targetType, targetAnnotations));
 	}
 
 	private @Nullable Object convert(@Nullable Object source, @Nullable TypeDescriptor sourceType,
@@ -125,6 +117,9 @@ private boolean canConvert(@Nullable TypeDescriptor sourceType, TypeDescriptor t
 				}
 			}
 		}
+		if (source == null) {
+			return null;
+		}
 		throw (failure != null) ? failure : new ConverterNotFoundException(sourceType, targetType);
 	}
 

core/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/ValueObjectBinder.java

@@ -61,6 +61,7 @@
  * @author Stephane Nicoll
  * @author Phillip Webb
  * @author Scott Frederick
+ * @author Ondřej Světlík
  */
 class ValueObjectBinder implements DataObjectBinder {
 
@@ -132,12 +133,7 @@ public <T> void onUnableToCreateInstance(Bindable<T> target, Context context, Ru
 				return convertDefaultValue(context.getConverter(), defaultValue, type, annotations);
 			}
 		}
-		return convertNullValue(context, type);
-	}
-
-	private <T> @Nullable T convertNullValue(Binder.Context context, ResolvableType type, Annotation... annotations) {
-		BindConverter converter = context.getConverter();
-		return converter.convertNullValue(type, annotations);
+		return context.getConverter().convert(null, type);
 	}
 
 	private <T> @Nullable T convertDefaultValue(BindConverter converter, String[] defaultValue, ResolvableType type,

core/spring-boot/src/test/java/org/springframework/boot/context/properties/bind/ValueObjectBinderTests.java

@@ -50,6 +50,7 @@
  * @author Phillip Webb
  * @author Pavel Anisimov
  * @author Yanming Zhou
+ * @author Ondřej Světlík
  */
 class ValueObjectBinderTests {