Remove Nullable annotation

[wonwoo]

No description provided.

[wilkinsona]

Thanks for the PR. The intent of the proposed changes isn't clear to me. Can you please describe what you are aiming to harmonise? Note that we have an issue open to add @Nullable across Spring Boot's API. It is something that we want to do, but we want to do it in one go across the entire API.

[wonwoo]

nullable annotation is declared another convert method. in harmony with them..

But if you change the entire api at once, this pr is closed.

[wilkinsona]

Thanks for the clarification. The existing usages of @Nullable on a Converter are only in some test code. I'm also not sure why it's there and think I could probably be removed.

@snicoll, can you recall why we have @Nullable here:

spring-boot/spring-boot-project/spring-boot-test-autoconfigure/src/test/java/org/springframework/boot/test/autoconfigure/web/reactive/webclient/ExampleIdConverter.java

Lines 42 to 50 in e8fef97

	@Nullable
	@Override
	public Object convert(@Nullable Object source, TypeDescriptor sourceType,
	TypeDescriptor targetType) {
	if (source == null) {
	return null;
	}
	return new ExampleId(UUID.fromString((String) source));
	}

[snicoll]

It is probably a mistake, IntelliJ IDEA can add the annotation automatically when you override a method.

[wonwoo]

spring-boot/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/convert/ArrayToDelimitedStringConverter.java

Lines 53 to 59 in ca0de43

	@Override
	@Nullable
	public Object convert(@Nullable Object source, TypeDescriptor sourceType,
	TypeDescriptor targetType) {
	List<Object> list = Arrays.asList(ObjectUtils.toObjectArray(source));
	return this.delegate.convert(list, sourceType, targetType);
	}

ArrayToDelimitedStringConverter, DelimitedStringToArrayConverter, DelimitedStringToCollectionConverter

Nullable Annotations are declared in the class

[wilkinsona]

Well spotted. They shouldn't be there either (and are providing no benefit as it's a package-private class). Would you like to repurpose this PR to remove them? The only place where @Nullable should be used is to allow actuator endpoint operations to indicate that an input is optional.

[wilkinsona]

Thanks very much for making your first contribution to Spring Boot, @wonwoo. The proposed changes have been merged into 2.1.x and forwards into master.