SpringBoot如何對LocalDateTime進(jìn)行格式化并解析
【1】格式化后臺傳給前端的日期
首先第一點需要知道的是springboot默認(rèn)依賴的json框架是jackson。
當(dāng)使用@ResponseBody注解返回json格式數(shù)據(jù)時就是該框架在起作用。
SpringBoot對Date/DateTime配置
如果字段屬性是Date而非LocalDateTime時,通常我們會在application.properties里面配置如下:
spring.mvc.date-format=yyyy-MM-dd HH:mm:ss spring.jackson.date-format=yyyy-MM-dd HH:mm:ss spring.jackson.time-zone=GMT+8 spring.jackson.serialization.write-dates-as-timestamps=false
如下圖所示,spring.jackson開頭的配置會被JacksonProperties類獲取進(jìn)行使用。
當(dāng)返回json格式的時候,Jackson就會根據(jù)配置文件中日期格式化的配置對結(jié)果進(jìn)行處理。
但是如果字段屬性為LocalDateTime呢?這種配置就失去了作用。
第一種方式:配置localDateTimeSerializer
這時候建議配置如下:
/** * Created by jianggc at 2020/7/1. */ @Configuration public class LocalDateTimeSerializerConfig { @Value("${spring.jackson.date-format:yyyy-MM-dd HH:mm:ss}") private String pattern; // localDateTime 序列化器 @Bean public LocalDateTimeSerializer localDateTimeSerializer() { return new LocalDateTimeSerializer(DateTimeFormatter.ofPattern(pattern)); } // localDateTime 反序列化器 @Bean public LocalDateTimeDeserializer localDateTimeDeserializer() { return new LocalDateTimeDeserializer(DateTimeFormatter.ofPattern(pattern)); } @Bean public Jackson2ObjectMapperBuilderCustomizer jackson2ObjectMapperBuilderCustomizer() { // return new Jackson2ObjectMapperBuilderCustomizer() { // @Override // public void customize(Jackson2ObjectMapperBuilder jacksonObjectMapperBuilder) { jacksonObjectMapperBuilder.featuresToDisable(SerializationFeature.FAIL_ON_EMPTY_BEANS); // jacksonObjectMapperBuilder.serializerByType(LocalDateTime.class, localDateTimeSerializer()); // jacksonObjectMapperBuilder.deserializerByType(LocalDateTime.class,localDateTimeDeserializer()); // } // }; //這種方式同上 return builder -> { builder.serializerByType(LocalDateTime.class, localDateTimeSerializer()); builder.deserializerByType(LocalDateTime.class,localDateTimeDeserializer()); builder.simpleDateFormat(pattern); }; } }
第二種方式:@JsonFormat
這種配置方式自然是全局的,如果想針對某個字段特殊處理,可以在類字段上面添加注解@JsonFormat:
@JsonFormat( pattern = "yyyy-MM-dd HH:mm:ss",timezone="GMT+8") private Date createdDate; @JsonFormat( pattern = "yyyy-MM-dd HH:mm:ss") private LocalDateTime createdTime;
【2】前臺傳String格式日期給后臺
如下所示,前臺傳參2020-08-30 11:11:11,后臺使用LocalDateTime 接收。
通常會報錯類似如下:
nested exception is org.springframework.core.convert.ConversionFailedException:
Failed to convert from type [java.lang.String] to type [java.time.LocalDateTime ]
很顯然是在參數(shù)綁定的時候沒有找到合適的轉(zhuǎn)換器把String轉(zhuǎn)換為對應(yīng)的格式。
① 配置全局的日期轉(zhuǎn)換器localDateTimeConvert
@Bean public Converter<String, LocalDateTime> localDateTimeConvert() { return new Converter<String, LocalDateTime>() { @Override public LocalDateTime convert(String source) { DateTimeFormatter df = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"); LocalDateTime dateTime = null; try { //2020-01-01 00:00:00 switch (source.length()){ case 10: logger.debug("傳過來的是日期格式:{}",source); source=source+" 00:00:00"; break; case 13: logger.debug("傳過來的是日期 小時格式:{}",source); source=source+":00:00"; break; case 16: logger.debug("傳過來的是日期 小時:分鐘格式:{}",source); source=source+":00"; break; } dateTime = LocalDateTime.parse(source, df); } catch (Exception e) { logger.error(e.getMessage(),e); } return dateTime; } }; }
實現(xiàn)原理簡要描述
在進(jìn)行參數(shù)綁定的時候,會使用WebDataBinder對象。而創(chuàng)建WebDataBinder對象時,會遍歷DefaultDataBinderFactory.initializer,使用其WebBindingInitializer initializer對WebDataBinder對象進(jìn)行初始化。
初始化方法具體可見ConfigurableWebBindingInitializer.initBinder(WebDataBinder binder),源碼如下:
public void initBinder(WebDataBinder binder) { binder.setAutoGrowNestedPaths(this.autoGrowNestedPaths); if (this.directFieldAccess) { binder.initDirectFieldAccess(); } //設(shè)置messageCodesResolver if (this.messageCodesResolver != null) { binder.setMessageCodesResolver(this.messageCodesResolver); } //設(shè)置bindingErrorProcessor if (this.bindingErrorProcessor != null) { binder.setBindingErrorProcessor(this.bindingErrorProcessor); } //設(shè)置validator if (this.validator != null && binder.getTarget() != null && this.validator.supports(binder.getTarget().getClass())) { binder.setValidator(this.validator); } //設(shè)置conversionService if (this.conversionService != null) { binder.setConversionService(this.conversionService); } if (this.propertyEditorRegistrars != null) { PropertyEditorRegistrar[] var2 = this.propertyEditorRegistrars; int var3 = var2.length; for(int var4 = 0; var4 < var3; ++var4) { PropertyEditorRegistrar propertyEditorRegistrar = var2[var4]; propertyEditorRegistrar.registerCustomEditors(binder); } } }
而conversionService中包含了許多的convert-類型格式化器。在WebDataBinder進(jìn)行參數(shù)綁定的時候就會使用不同的格式化器即不同的convert進(jìn)行參數(shù)類型轉(zhuǎn)換。
關(guān)于參數(shù)綁定的過程,有興趣的可以跟蹤DataBinder.doBind方法,在這個過程中會對前臺傳輸?shù)闹颠M(jìn)行類型轉(zhuǎn)換為目標(biāo)參數(shù)需要的類型。自定義的localDateTimeConvert也是在這里被用到的。
如下所示前臺傳String格式給后臺參數(shù)endDate,參數(shù)類型為java.time.LocalDateTime。
找到我們自定義的converter
調(diào)用convert進(jìn)行類型轉(zhuǎn)換:
可以看到轉(zhuǎn)換后的結(jié)果為:
② 配置日期格式化器
/** * yyyy-MM-dd HH:mm:ss String-localDateTime * @return */ @Bean public Formatter<LocalDateTime> localDateTimeFormatter() { return new Formatter<LocalDateTime>() { @Override public LocalDateTime parse(String text, Locale locale) throws ParseException { return LocalDateTime.parse(text, DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")); } @Override public String print(LocalDateTime localDateTime, Locale locale) { DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"); return formatter.format(localDateTime); } }; }
自定義的格式化器會在SpringBoot啟動時自動化配置過程中被加入,具體可以參考如下代碼。
WebMvcAutoConfiguration.mvcConversionService:
@Bean @Override public FormattingConversionService mvcConversionService() { WebConversionService conversionService = new WebConversionService(this.mvcProperties.getDateFormat()); addFormatters(conversionService); return conversionService; }
【3】convert是什么時候添加到ConversionService中的?
① SpringBoot啟動的時候運(yùn)行run方法
其會走到SpringApplication.configureEnvironment方法處:
protected void configureEnvironment(ConfigurableEnvironment environment, String[] args) { if (this.addConversionService) { //從這里跟蹤 ConversionService conversionService = ApplicationConversionService.getSharedInstance(); environment.setConversionService((ConfigurableConversionService)conversionService); } this.configurePropertySources(environment, args); this.configureProfiles(environment, args); }
② 嘗試獲取ConversionService
ApplicationConversionService.getSharedInstance如下所示,這里可以看到其使用了設(shè)計模式中的懶漢式之雙重校驗鎖來獲取單例。
public static ConversionService getSharedInstance() { ApplicationConversionService sharedInstance = sharedInstance; if (sharedInstance == null) { Class var1 = ApplicationConversionService.class; synchronized(ApplicationConversionService.class) { sharedInstance = sharedInstance; if (sharedInstance == null) { sharedInstance = new ApplicationConversionService(); sharedInstance = sharedInstance; } } } return sharedInstance; }
③ 獲取ApplicationConversionService
繼續(xù)對象創(chuàng)建過程會發(fā)現(xiàn)其走到了configure處:
public ApplicationConversionService(StringValueResolver embeddedValueResolver) { if (embeddedValueResolver != null) { this.setEmbeddedValueResolver(embeddedValueResolver); } //我們從這里繼續(xù)跟進(jìn) configure(this); }
這里我們順帶看一下ApplicationConversionService的類繼承示意圖(其不只是可以作為ConversionService還可以作為ConverterRegistry與FormatterRegistry):
④ ApplicationConversionService.configure
創(chuàng)建ApplicationConversionService時會對其進(jìn)行配置,這里很重要。其會注入默認(rèn)的Converter和Formatter:
public static void configure(FormatterRegistry registry) { DefaultConversionService.addDefaultConverters(registry); DefaultFormattingConversionService.addDefaultFormatters(registry); addApplicationFormatters(registry); addApplicationConverters(registry); }
⑤ DefaultConversionService.addDefaultConverters
該方法執(zhí)行完,會添加52個類型轉(zhuǎn)換器:
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)); }
addScalarConverters(converterRegistry);如下所示:
private static void addScalarConverters(ConverterRegistry converterRegistry) { converterRegistry.addConverterFactory(new NumberToNumberConverterFactory()); converterRegistry.addConverterFactory(new StringToNumberConverterFactory()); converterRegistry.addConverter(Number.class, String.class, new ObjectToStringConverter()); converterRegistry.addConverter(new StringToCharacterConverter()); converterRegistry.addConverter(Character.class, String.class, new ObjectToStringConverter()); converterRegistry.addConverter(new NumberToCharacterConverter()); converterRegistry.addConverterFactory(new CharacterToNumberFactory()); converterRegistry.addConverter(new StringToBooleanConverter()); converterRegistry.addConverter(Boolean.class, String.class, new ObjectToStringConverter()); converterRegistry.addConverterFactory(new StringToEnumConverterFactory()); converterRegistry.addConverter(new EnumToStringConverter((ConversionService) converterRegistry)); converterRegistry.addConverterFactory(new IntegerToEnumConverterFactory()); converterRegistry.addConverter(new EnumToIntegerConverter((ConversionService) converterRegistry)); converterRegistry.addConverter(new StringToLocaleConverter()); converterRegistry.addConverter(Locale.class, String.class, new ObjectToStringConverter()); converterRegistry.addConverter(new StringToCharsetConverter()); converterRegistry.addConverter(Charset.class, String.class, new ObjectToStringConverter()); converterRegistry.addConverter(new StringToCurrencyConverter()); converterRegistry.addConverter(Currency.class, String.class, new ObjectToStringConverter()); converterRegistry.addConverter(new StringToPropertiesConverter()); converterRegistry.addConverter(new PropertiesToStringConverter()); converterRegistry.addConverter(new StringToUUIDConverter()); converterRegistry.addConverter(UUID.class, String.class, new ObjectToStringConverter()); }
這里會添加23個類型轉(zhuǎn)換器:
添加集合處理的類型轉(zhuǎn)換器(這里會添加17個類型轉(zhuǎn)換器):
public static void addCollectionConverters(ConverterRegistry converterRegistry) { ConversionService conversionService = (ConversionService) converterRegistry; converterRegistry.addConverter(new ArrayToCollectionConverter(conversionService)); converterRegistry.addConverter(new CollectionToArrayConverter(conversionService)); converterRegistry.addConverter(new ArrayToArrayConverter(conversionService)); converterRegistry.addConverter(new CollectionToCollectionConverter(conversionService)); converterRegistry.addConverter(new MapToMapConverter(conversionService)); converterRegistry.addConverter(new ArrayToStringConverter(conversionService)); converterRegistry.addConverter(new StringToArrayConverter(conversionService)); converterRegistry.addConverter(new ArrayToObjectConverter(conversionService)); converterRegistry.addConverter(new ObjectToArrayConverter(conversionService)); converterRegistry.addConverter(new CollectionToStringConverter(conversionService)); converterRegistry.addConverter(new StringToCollectionConverter(conversionService)); converterRegistry.addConverter(new CollectionToObjectConverter(conversionService)); converterRegistry.addConverter(new ObjectToCollectionConverter(conversionService)); converterRegistry.addConverter(new StreamConverter(conversionService)); }
⑥ addDefaultFormatters添加格式化器
/** * Add formatters appropriate for most environments: including number formatters, * JSR-354 Money & Currency formatters, JSR-310 Date-Time and/or Joda-Time formatters, * depending on the presence of the corresponding API on the classpath. * @param formatterRegistry the service to register default formatters with */ 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 JodaTimeFormatterRegistrar().registerFormatters(formatterRegistry); } else { // regular DateFormat-based Date, Calendar, Long converters new DateFormatterRegistrar().registerFormatters(formatterRegistry); } }
DateTimeFormatterRegistrar.registerFormatters
@Override public void registerFormatters(FormatterRegistry registry) { DateTimeConverters.registerConverters(registry); DateTimeFormatter df = getFormatter(Type.DATE); DateTimeFormatter tf = getFormatter(Type.TIME); DateTimeFormatter dtf = getFormatter(Type.DATE_TIME); // Efficient ISO_LOCAL_* variants for printing since they are twice as fast... registry.addFormatterForFieldType(LocalDate.class, new TemporalAccessorPrinter( df == DateTimeFormatter.ISO_DATE ? DateTimeFormatter.ISO_LOCAL_DATE : df), new TemporalAccessorParser(LocalDate.class, df)); registry.addFormatterForFieldType(LocalTime.class, new TemporalAccessorPrinter( tf == DateTimeFormatter.ISO_TIME ? DateTimeFormatter.ISO_LOCAL_TIME : tf), new TemporalAccessorParser(LocalTime.class, tf)); registry.addFormatterForFieldType(LocalDateTime.class, new TemporalAccessorPrinter( dtf == DateTimeFormatter.ISO_DATE_TIME ? DateTimeFormatter.ISO_LOCAL_DATE_TIME : dtf), new TemporalAccessorParser(LocalDateTime.class, dtf)); registry.addFormatterForFieldType(ZonedDateTime.class, new TemporalAccessorPrinter(dtf), new TemporalAccessorParser(ZonedDateTime.class, dtf)); registry.addFormatterForFieldType(OffsetDateTime.class, new TemporalAccessorPrinter(dtf), new TemporalAccessorParser(OffsetDateTime.class, dtf)); registry.addFormatterForFieldType(OffsetTime.class, new TemporalAccessorPrinter(tf), new TemporalAccessorParser(OffsetTime.class, tf)); registry.addFormatterForFieldType(Instant.class, new InstantFormatter()); registry.addFormatterForFieldType(Period.class, new PeriodFormatter()); registry.addFormatterForFieldType(Duration.class, new DurationFormatter()); registry.addFormatterForFieldType(Year.class, new YearFormatter()); registry.addFormatterForFieldType(Month.class, new MonthFormatter()); registry.addFormatterForFieldType(YearMonth.class, new YearMonthFormatter()); registry.addFormatterForFieldType(MonthDay.class, new MonthDayFormatter()); registry.addFormatterForFieldAnnotation(new Jsr310DateTimeFormatAnnotationFormatterFactory()); }
DateTimeConverters.registerConverters
public static void registerConverters(ConverterRegistry registry) { DateFormatterRegistrar.addDateConverters(registry); registry.addConverter(new LocalDateTimeToLocalDateConverter()); registry.addConverter(new LocalDateTimeToLocalTimeConverter()); registry.addConverter(new ZonedDateTimeToLocalDateConverter()); registry.addConverter(new ZonedDateTimeToLocalTimeConverter()); registry.addConverter(new ZonedDateTimeToLocalDateTimeConverter()); registry.addConverter(new ZonedDateTimeToOffsetDateTimeConverter()); registry.addConverter(new ZonedDateTimeToInstantConverter()); registry.addConverter(new OffsetDateTimeToLocalDateConverter()); registry.addConverter(new OffsetDateTimeToLocalTimeConverter()); registry.addConverter(new OffsetDateTimeToLocalDateTimeConverter()); registry.addConverter(new OffsetDateTimeToZonedDateTimeConverter()); registry.addConverter(new OffsetDateTimeToInstantConverter()); registry.addConverter(new CalendarToZonedDateTimeConverter()); registry.addConverter(new CalendarToOffsetDateTimeConverter()); registry.addConverter(new CalendarToLocalDateConverter()); registry.addConverter(new CalendarToLocalTimeConverter()); registry.addConverter(new CalendarToLocalDateTimeConverter()); registry.addConverter(new CalendarToInstantConverter()); registry.addConverter(new LongToInstantConverter()); registry.addConverter(new InstantToLongConverter()); }
DateFormatterRegistrar.addDateConverters
public static void addDateConverters(ConverterRegistry converterRegistry) { converterRegistry.addConverter(new DateToLongConverter()); converterRegistry.addConverter(new DateToCalendarConverter()); converterRegistry.addConverter(new CalendarToDateConverter()); converterRegistry.addConverter(new CalendarToLongConverter()); converterRegistry.addConverter(new LongToDateConverter()); converterRegistry.addConverter(new LongToCalendarConverter()); }
⑦ addApplicationFormatters(registry)
添加全局格式化器:
public static void addApplicationFormatters(FormatterRegistry registry) { registry.addFormatter(new CharArrayFormatter()); registry.addFormatter(new InetAddressFormatter()); registry.addFormatter(new IsoOffsetFormatter()); }
⑧ addApplicationConverters(registry)
添加全局類型轉(zhuǎn)換器:
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 StringToDataSizeConverter()); registry.addConverter(new NumberToDataSizeConverter()); registry.addConverter(new StringToFileConverter()); registry.addConverterFactory(new LenientStringToEnumConverterFactory()); registry.addConverterFactory(new LenientBooleanToEnumConverterFactory()); } public static void addDelimitedStringConverters(ConverterRegistry registry) { ConversionService service = (ConversionService)registry; registry.addConverter(new ArrayToDelimitedStringConverter(service)); registry.addConverter(new CollectionToDelimitedStringConverter(service)); registry.addConverter(new DelimitedStringToArrayConverter(service)); registry.addConverter(new DelimitedStringToCollectionConverter(service)); }
以上為個人經(jīng)驗,希望能給大家一個參考,也希望大家多多支持腳本之家。
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