Springboot 转化器

Springboot 提供了很多转化器：
其中有ApplicationConversionService：extends FormattingConversionService。

	public static void addApplicationConverters(ConverterRegistry registry) {
		addDelimitedStringConverters(registry);
		registry.addConverter(new StringToDurationConverter());
		registry.addConverter(new DurationToStringConverter());
		registry.addConverter(new NumberToDurationConverter());
		registry.addConverter(new DurationToNumberConverter());
		registry.addConverter(new StringToPeriodConverter());
		registry.addConverter(new PeriodToStringConverter());
		registry.addConverter(new NumberToPeriodConverter());
		registry.addConverter(new StringToDataSizeConverter());
		registry.addConverter(new NumberToDataSizeConverter());
		registry.addConverter(new StringToFileConverter());
		registry.addConverter(new InputStreamSourceToByteArrayConverter());
		registry.addConverterFactory(new LenientStringToEnumConverterFactory());
		registry.addConverterFactory(new LenientBooleanToEnumConverterFactory());
		if (registry instanceof ConversionService conversionService) {
			addApplicationConverters(registry, conversionService);
		}
	}

	private static void addApplicationConverters(ConverterRegistry registry, ConversionService conversionService) {
		registry.addConverter(new CharSequenceToObjectConverter(conversionService));
	}

转化为一个数组为delimited String.

final class ArrayToDelimitedStringConverter implements ConditionalGenericConverter {

	private final CollectionToDelimitedStringConverter delegate;

	ArrayToDelimitedStringConverter(ConversionService conversionService) {
		this.delegate = new CollectionToDelimitedStringConverter(conversionService);
	}

	@Override
	public Set<ConvertiblePair> getConvertibleTypes() {
		return Collections.singleton(new ConvertiblePair(Object[].class, String.class));
	}

	@Override
	public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
		return this.delegate.matches(sourceType, targetType);
	}

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

}

本质上就是各种数据类型之间的转化：