Mapstruct对象插入数据库某个字段总是为空的bug详解

@Autowired
    private PersonService personService;
    public void test1(){
        Person person = personService.findById(1L);
        PersonDto personDto = PersonMapper.INSTANCE.personToPersonDto(person);
        personService.insert(personDto);
    }

PersonDto personDto = PersonMapper.INSTANCE.personToPersonDto(person);

public class PersonMapperImpl implements PersonMapper {
    public PersonMapperImpl() {
    }
    public PersonDto personToPersonDto(Person person) {
        if (person == null) {
            return null;
        } else {
            PersonDtoBuilder personDto = PersonDto.builder();
            personDto.name(person.getName());
            return personDto.build();
        }
    }
}

mvnDebug clean compile

private void processMapperTypeElement(ProcessorContext context, TypeElement mapperTypeElement) {
    Object model = null;
    for ( ModelElementProcessor<?, ?> processor : getProcessors() ) {
        try {
            model = process( context, processor, mapperTypeElement, model );
        }
        catch ( AnnotationProcessingException e ) {
           //省略
        }
    }
}

@Override
public Mapper process(ProcessorContext context, TypeElement mapperTypeElement, List<SourceMethod> sourceModel) {
    this.elementUtils = context.getElementUtils();
    this.typeUtils = context.getTypeUtils();
    this.messager =
        new MapperAnnotatedFormattingMessenger( context.getMessager(), mapperTypeElement, context.getTypeUtils() );
    this.options = context.getOptions();
    this.versionInformation = context.getVersionInformation();
    this.typeFactory = context.getTypeFactory();
    this.accessorNaming = context.getAccessorNaming();
    MapperOptions mapperOptions = MapperOptions.getInstanceOn( mapperTypeElement, context.getOptions() );
    List<MapperReference> mapperReferences = initReferencedMappers( mapperTypeElement, mapperOptions );
    MappingBuilderContext ctx = new MappingBuilderContext(
        typeFactory,
        elementUtils,
        typeUtils,
        messager,
        accessorNaming,
        context.getEnumMappingStrategy(),
        context.getEnumTransformationStrategies(),
        options,
        new MappingResolverImpl(
            messager,
            elementUtils,
            typeUtils,
            typeFactory,
            new ArrayList<>( sourceModel ),
            mapperReferences,
            options.isVerbose()
        ),
        mapperTypeElement,
        //sourceModel is passed only to fetch the after/before mapping methods in lifecycleCallbackFactory;
        //Consider removing those methods directly into MappingBuilderContext.
        Collections.unmodifiableList( sourceModel ),
        mapperReferences
    );
    this.mappingContext = ctx;
    return getMapper( mapperTypeElement, mapperOptions, sourceModel );
}

List<MappingMethod> mappingMethods = getMappingMethods( mapperOptions, methods );

List<Accessor> candidates = new ArrayList<>( getSetters() );