Spring中的ConversionService源码解析

public interface Printer<T> {

	String print(T object, Locale locale);
	
}

public interface Parser<T> {

	T parse(String text, Locale locale) throws ParseException;

}

public DefaultFormattingConversionService(
			@Nullable StringValueResolver embeddedValueResolver, boolean registerDefaultFormatters) {

		if (embeddedValueResolver != null) {
			setEmbeddedValueResolver(embeddedValueResolver);
		}
		DefaultConversionService.addDefaultConverters(this);
		if (registerDefaultFormatters) {
			addDefaultFormatters(this);
		}
	}

	public static void addDefaultConverters(ConverterRegistry converterRegistry) {
		addScalarConverters(converterRegistry);
		addCollectionConverters(converterRegistry);

		converterRegistry.addConverter(new ByteBufferConverter((ConversionService) converterRegistry));
		converterRegistry.addConverter(new StringToTimeZoneConverter());
		converterRegistry.addConverter(new ZoneIdToTimeZoneConverter());
		converterRegistry.addConverter(new ZonedDateTimeToCalendarConverter());

		converterRegistry.addConverter(new ObjectToObjectConverter());
		converterRegistry.addConverter(new IdToEntityConverter((ConversionService) converterRegistry));
		converterRegistry.addConverter(new FallbackObjectToStringConverter());
		converterRegistry.addConverter(new ObjectToOptionalConverter((ConversionService) converterRegistry));
	}

	public static void addDefaultFormatters(FormatterRegistry formatterRegistry) {
		// Default handling of number values
		formatterRegistry.addFormatterForFieldAnnotation(new NumberFormatAnnotationFormatterFactory());

		// Default handling of monetary values
		if (jsr354Present) {
			formatterRegistry.addFormatter(new CurrencyUnitFormatter());
			formatterRegistry.addFormatter(new MonetaryAmountFormatter());
			formatterRegistry.addFormatterForFieldAnnotation(new Jsr354NumberFormatAnnotationFormatterFactory());
		}

		// Default handling of date-time values

		// just handling JSR-310 specific date and time types
		new DateTimeFormatterRegistrar().registerFormatters(formatterRegistry);

		if (jodaTimePresent) {
			// handles Joda-specific types as well as Date, Calendar, Long
			new org.springframework.format.datetime.joda.JodaTimeFormatterRegistrar().registerFormatters(formatterRegistry);
		}
		else {
			// regular DateFormat-based Date, Calendar, Long converters
			new DateFormatterRegistrar().registerFormatters(formatterRegistry);
		}
	}

	public static void main(String[] args) {

		AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class);
		UserService userService = (UserService) applicationContext.getBean("userService");

		FormattingConversionService conversionService = new DefaultFormattingConversionService();
		
		//String -> ArrayList
		System.out.println(conversionService.convert("1,2,3,4", ArrayList.class));
		
		//boolean -> String
		System.out.println(conversionService.convert(true,String.class));
		
		//自定义了一个格式化器，OrderService -> String ,String -> OrderService
		conversionService.addFormatter(new Formatter<OrderService>() {
			private ObjectMapper objectMapper = new ObjectMapper();
			@Override
			public String print(OrderService object, Locale locale) {
				try {
					return objectMapper.writeValueAsString(object);
				} catch (JsonProcessingException e) {
					throw new RuntimeException(e);
				}
			}

			@Override
			public OrderService parse(String text, Locale locale) throws ParseException {
				try {
					return  objectMapper.readValue(text,OrderService.class);
				} catch (JsonProcessingException e) {
					throw new RuntimeException(e);
				}
			}
		});
		String result = conversionService.convert(userService.getOrderService(),String.class);
		System.out.println(result);
		OrderService orderService = conversionService.convert(result, OrderService.class);
		System.out.println(orderService);
	}