SpringBoot整合LocalDateTime的过程
目录
- 一、为什么使用LocalDateTime
- 二、使用LocalDateTime遇到的问题
- 三、异常源码分析
- 四、解决思路
- 4.1、GET请求解决思路
- 4.2、POST请求解决思路
- 五、解决方案落地
- 5.1、GET请求解决方案
- 5.2、POST请求解决方案
一、为什么使用LocalDateTime
LocalDateTime 和 Date 是 Java 中处理日期和时间的两种不同的类,在 JDK8 中引入了 java.time 包。LocalDateTime 相比 Date 有一些优势,主要体现在以下几个方面:
- 不可变性:
- LocalDateTime 是不可变的类,一旦创建就不能被修改。任何对 LocalDateTime 的操作都会返回一个新的对象,而不会修改原始对象。这有助于避免在多线程环境中的并发问题。
- 线程安全性:
- 由于 LocalDateTime 是不可变的,因此它天然具有线程安全性,可以在多线程环境中安全使用。
- 可读性和易用性:
- LocalDateTime 提供了更加清晰和直观的API,使得处理日期和时间更加易读、易用。例如,通过使用方法链式调用,可以轻松地执行各种操作,而不需要复杂的日期格式化和解析。
- 更好的API设计:
- LocalDateTime 提供了更丰富、灵活和易用的API,允许进行各种日期和时间的操作,例如增减天数、小时、分钟等。而 Date 的 API相对较为古老和不够直观。
- 时区处理:
- LocalDateTime 能够更好地处理时区信息,通过 ZonedDateTime 类可以轻松转换到不同的时区。而 Dat编程客栈e 类在处理时区时较为复杂,通常需要使用 Calendar 类。
总的来说,LocalDateTime 提供了更现代、清晰和强大的日期和时间处理功能,使得开发者更容易编写可读性高且可维护性强的代码。在新的代码中,特别是在使用 JDK 8 及更新版本的项目中,推荐使用 LocalDateTime 替代 Date。
二、使用LocalDateTime遇到的问题
众所周知,SpringBoot会自动对前端的传值进行解析,将 HttpServletRequest 中的请求内容,转换成后端 Controoler 控制器中的实体类参数,但在实际使用 LocalDateTime 作为参数时,当前端传入日期格式为 yyyy-MM-dd HH:mm:ss 时,我们会发现 SpringandroidBoot 好像不能正常工作了,下面是两个问题例子。
GET请求使用 LocalDateTime 作为参数
下面是使用 @RequestParam 和 @PathVariable 两种最常见的用法示例
@RestController public class LocalDateTimeController { @GetMapping("/resolveRequestParamDateTime") public void resolveRequestParamDateTime(@RequestParam LocalDateTime dateTime) { System.out.println("ok"); } @GetMapping("/resolvePathVariableDateTime/{dateTime}") public void resolvePathVariableDateTime(@PathVariable LocalDateTime dateTime) { System.out.println("ok"); } }
点击运行,无论是第一个还是第二个方法,都会出现如下异常
org.springframework.web.method.annotation.MethodArgumentTypeMismatchException: Failed to convert value of type 'java.lang.String' to required type 'java.time.LocalDateTime'; nested exception is org.springframework.core.convert.ConversionFailedException: Failed to convert from type [java.lang.String] to type [@org.springframework.web.bind.annotation.PathVariable java.time.LocalDateTime] for value '2023-01-01 12:12:12'; nested exception is java.lang.IllegalArgumentException: Parse attempt failed for value [2023-01-01 12:12:12]
at org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver.resolveArgument(AbstractNamedValueMethodArgumentResolver.java:133) at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:121)Caused by: org.springframework.core.convert.ConversionFailedException: Failed to convert from type [java.lang.String] to type [@org.springframework.web.bind.annotation.PathVariable java.time.LocalDateTime] for value '2023-01-01 12:12:12'; nested exception is java.lang.IllegalArgumentException: Parse attempt failed for value [2023-01-01 12:12:12] at org.springframework.core.convert.support.ConversionUtils.invokeConverter(ConversionUtils.java:47) at org.springframework.core.convert.support.GenericConversionService.convert(GenericConversionService.java:191)Caused by: java.lang.IllegalArgumentException: Parse attempt failed for value [2023-01-01 12:12:12] at org.springframework.format.support.FormattingConversionService$ParserConverter.convert(FormattingConversionService.java:223)Caused by: java.time.format.DateTimeParseException: Text '2023-01-01 12:12:12' could not be parsed at index 2 at java.time.format.DateTimeFormatter.parseResolved0(DateTimeFormatter.java:1949)
POST请求体中使用 LocalDateTime 作为参数 下面是使用 @RequestBody 的示例
@RestController public class LocalDateTimeController { @PostMapping("/resolveBodyDateTime") public void resolveBodyDateTime(@RequestBody ResolveBody body) { System.out.println("ok"); } @Data private static class ResolveBody { private LocalDateTime dateTime; } }
点击运行,会出现如下异常
org.springframework.http.converter.HttpMessageNotReadableException: jsON parse error: Expected array or string.; nested exception is com.fasterXML.jackson.databind.exc.MismatchedInputException: Expected array or string.
at [Source: (PushbackInputStream); line: 1, column: 1] at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:245) at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.read(AbstractJackson2HttpMessageConverter.java:227) at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodArgumentResolver.readwithMessageConverters(AbstractMessageConverterMethodArgumentResolver.java:205) at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.readWithMessageConverters(RequestResponseBodyMethodProcessor.java:158) at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.resolveArgument(RequestResponseBodyMethodProcessor.java:131) at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:121)Caused by: com.fasterxml.jackson.databind.exc.MismatchedInputException: Expected array or string. at [Source: (PushbackInputStream); line: 1, column: 1] at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:59) at com.fasterxml.jackson.databind.DeserializationContext.reportInputMismatch(DeserializationContext.java:1442)
简单分析
观察堆栈错误信息,在使用 GET 请求时抛出的异常的 MethodArgumentTypeMismatchException ,而使用 POST请求时抛出的异常是 HttpMessageNotReadableException 。 二者最外层抛出的异常不一样,但是我们继续往下看最内层抛出的异常, GET 请求的报错很明显就是 String 类型不能被转换为 LocalDateTime 类型抛出的异常,POST请求抛出的是 jackson 反序列化类型不匹配的异常。 通过分析可得,上述 GET 和 POST 请求的报错,都是由于 SpringBoot 未能正常将参数中 String 类型转换为 LocalDateTime 类型抛出的。
三、异常源码分析
通过堆栈信息可以看出,我们的请求链路在进行参数解析,也就是走到spring mvc 的HandlerMethodArgumentResolverComposite.resolveArgument()这个方法时发生的异常,从这个方法入手debug打断点依次往下执行,一直走到最内层的堆栈位置,也就是实际进行参数解析的核心代码,下面列出实际参数解析代码。
GET请求
第13行就是实际的转换代码,走到这里时spring拿到的converter是通过WebMvcAutoConfiguration类自动装配注入的FormattingConversionService对象 ,但是这个converter默认情况下并不能将String转换为LocalDateTime
GenericConversionService.java类源码: @Nullable public Object convert(@Nullable Object source, @Nullable TypeDescriptor sourceType, TypeDescriptor targetType) { Assert.notNull(targetType, "Target type to convert to cannot be null"); if (sourceType == null) { Assert.isTrue(source == null, "Source must be [null] if source type == [null]"); return this.handleResult((TypeDescriptor)null, targetType, this.convertNullSource((TypeDescriptor)null, targetType)); } else if (source != null && !sourceType.getObjectType().isInstance(source)) { throw new IllegalArgumentException("Source to convert from must be an instance of [" + sourceType + "]; instead it was a [" + source.getClass().getName() + "]"); } else { GenericConverter converter = this.getConverter(sourceType, targetType); if (converter != null) { # 这里去做类型转换 Object result = ConversionUtils.invokeConverter(converter, source, sourceType, targetType); return this.handleResult(sourceType, targetType, result); } else { return this.handleConverterNotFound(source, sourceType, targetType); } } }
POST请求 在第11~12行就是实际的转换代码,走到这里时spring拿到的converter是 MappingJackson2HttpMessageConverter ,但是这个converter并不能将String转换为LocalDateTime
AbstractMessageConverterMethodArgumentResolver类源码: for (HttpMessageConverter<?> converter : this.messageConverters) { Class<HttpMessageConverter<?>> converterType = (Class<HttpMessageConverter<?>>) converter.getClass(); GenericHttpMessageConverter<?> genericConverter = (converter instanceof GenericHttpMessageConverter ? (GenericHttpMessageConverter<?>) converter : null); if (genericConverter != null ? genericConverter.canRead(targetType, contextClass, contentType) : (targetClass != null && converter.canRead(targetClass, contentType))) { if (message.hasBody()) { HttpInputMessage msgToUse = getAdvice().beforeBodyRead(message, parameter, targetType, converterType); # 这里去做类型转换 body = (genericConverter != null ? genericConverter.read(targetType, contextClass, msgToUse) : ((HttpMessageConverter<T>) converter).read(targetClass, msgToUse)); body = getAdvice().afterBodyRead(body, msgToUse, parameter, targetType, converterType); } else { body = getAdvice().handleEmptyBody(null, message, parameter, targetType, converterType); } break; } }
MappingJackson2HttpMessageConverter的read解析方法继续往后走,调用的是父类AbstractJackson2HttpMessageConverter的read方法,实际的解析方法就是第18行的ObjectMapper类的readValue方法
AbstractJackson2HttpMessageConverter类源码: @Override public Object read(Type type, @Nullable Class<?> contextClass, HttpInputMessage inputMessage) throws IOException, HttpMessageNotReadableException { JavaType javaType = getJavaType(type, contextClass); return readJavaType(javaType, inputMessage); } private Object readJavaType(JavaType javaType, HttpInputMessage inputMessage) throws IOException { try { if (inputMessage instanceof MappingJacksonInputMessage) { Class<?> deserializationView = ((MappingJacksonInputMessage) inputMessage).getDeserializationView(); if (deserializationView != null) { return this.objectMapper.readerWithView(deserializationView).forType(javaType). readValue(inputMessage.getBody()); } } # jackson实际解析 return this.objectMapper.readValue(inputMessage.getBody(), javaType); } catch (InvalidDefinitionException ex) { throw new HttpMessageConversionException("Type definition error: " + ex.getType(), ex); } catch (JsonProcessingException ex) { throw new HttpMessageNotReadableException("JSON parse error: " + ex.getOriginalMessage(), ex, inputMessage); } }
问题分析
SpringBoot GET请求参数类型转换使用的是GenericConversionService类里注册的一个个GenericConverter;String转LocalDateTime类型默认情况下的StringToLocalDateTimeConverter不能正常解析。
- SpringBoot POST请求参数类型转换使用的是AbstractMessageConverterMethodArgumentResolver类里List<HttpMessageConverter<?>> messageConverters里注册的一个个HttpMessageConverter;
- String转LocalDateTime类型默认情况下的MappingJackson2HttpMessageConverter不能正常解析,也就是默认的ObjectMapper不能正常解析。
四、解决思路
通过上述问题分析,下面有两种解决思路(推荐第二种)
通过配置使得默认的StringToLocalDateTimeConverter支持GET请求String转LocalDateTime类型,默认的MappingJackson2HttpMessageConverter支持POST请求String转LocalDateTime类型
spring注入GenericConverter类型的Bean支持GET请求String转LocalDateTime类型,注入ObjectMapper类型的Bean支持POST请求String转LocalDateTime类型
4.1、GET请求解决思路
GET请求解决思路:通过阅读源码,可以发现以下三种springboot为用户预留的实现方式:
application.yml配置
在2.3.x以上版本,springmvc增加了日期时间格式配置,并且可以将格式注册到对应的日期解析器中
WebMvcAutoConfiguration#EnableWebMvcConfiguration类源码 // springboot自动装配WebConversionService对象 @Bean public FormattingConversionService mvcConversionService() { WebMvcProperties.Format format = this.mvcProperties.getFormat(); WebConversionService conversionService = new WebConversionService((new DateTimeFormatters()).dateFormat(format.getDate()).timeFormat(format.getTime()).dateTimeFormat(format.getDateTime())); // 这里允许用户自定往容器中添加Converter this.addFormatters(conversionService); return conversionService; } WebConversionService类源码: private void addFormatters(DateTimeFormatters dateTimeFormatters) { // 这是默认情况下springboot自动注入的日期格式解析器 this.registerJsr310(dateTimeFormatters); this.registerJavaDate(dateTimeFormatters); }
使用@DateTimeFormat注解
DateTimeFormatterRegistrar类源码: public void registerFormatters(FormatterRegistry registry) { // 这里可以拿到application.yml配置文件指定的格式 DateTimeFormatter df = this.getFormatter(DateTimeFormatterRegistrar.Type.DATE); DateTimeFormatter tf = this.getFormatter(DateTimeFormatterRegistrar.Type.TIME); DateTimeFormatter dtf = this.getFormatter(DateTimeFormatterRegistrar.Type.DATE_TIME); 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 TephpmporalAccessorPrinter(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)); // 使用@DateTimeFormat注解来帮忙完成LocalDateTime类型的解析 registry.addFormatterForFieldAnnotation(new Jsr310DateTimeFormatAnnotationFormatterFactory()); }
向容器中添加自定义Converter
我们在WebConversionService对象自动装配方法中看到了这行代码:this.addFormatters(conversionService);
这其实就是springboot为用户预留的拓展方法,它支持用户向容器中添加自定义Converter
// WebMvcAutoConfiguration.WebMvcAutoConfigurationAdapter#addFormatters()方法 public void addFormatters(FormatterRegistry registry) { ApplicationConversionService.addBeans(registry, this.beanFactory); } // ApplicationConversionService#addBeans()方法 public static void addBeans(FormatterRegistry registry, ListableBeanFactory beanFactory) { Set<Object> beans = new LinkedHashSet(); beans.addAll(beanFactory.getBeansOfType(GenericConverter.class).values()); beans.addAll(beanFactory.getBeansOfType(Converter.class).values()); beans.addAll(beanFactory.getBeansOfType(Printer.class).values()); beans.addAll(beanFactory.getBeansOfType(Parser.class).values()); Iterator var3 = beans.iterator(); // spirngboot会扫描ioc容器中以下所有类型的bean,并添加到WebConversionService中 while(var3.hasNext()) { Object bean = var3.next(); if (bean instanceof GenericConverter) { registry.addConverter((GenericConverter)bean); } else if (bean instanceof Converter) { registry.addConverter((Converter)bean); } else if (bean instanceof Formatter) { registry.addFormatter((Formatter)bean); } else if (bean instanceof Printer) { registry.addPrinter((Printer)bean); } else if (bean instanceof Parser) { registry.addParser((Parser)bean); } } }
4.2、POST请求解决思路
通过异常源码分析我们可以得知,由于jackson也就是ObjectMapper对象在默认情况下并不能完成LocalDateTime类型的解析,所有需要对jackson进行配置;通过阅读源码,以下有两种解决方式:
配置类注入Jackson2ObjectMapperBuilderCustomizer类型的Bean对jackson进行配置(推荐)
JacksonAutoConfiguration#JacksonObjectMapperBuilderConfiguration类源码: @Configuration(proxyBeanMethods = false) @ConditionalOnClass(Jackson2ObjectMapperBuilder.class) static class JacksonObjectMapperBuilderConfiguration { @Bean @Scope("prototype") @ConditionalOnMissingBean Jackson2ObjectMapperBuilder jacksonObjectMapperBuilder(ApplicationContejavascriptxt applicationContext, List<Jackson2ObjectMapperBuilderCustomizer> customizers) { Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder(); builder.applicationContext(applicationContext); // ioc容器中获取所有Jackson2ObjectMapperBuilderCustomizer类型的bean, 调用customize方法配置Jackson2ObjectMapperBuilder customize(builder, customizers); return builder; } private void customize(Jackson2ObjectMapperBuilder builder, List<Jackson2ObjectMapperBuilderCustomizer> customizers) { for (Jackson2ObjectMapperBuilderCustomizer customizer : customizers) { customizer.customize(builder); } } }
直接注入ObjectMapper类型的Bean进行覆盖
JacksonAutoConfiguration#JacksonObjectMapperConfiguration类源码 @Configuration(proxyBeanMethods = false) @ConditionalOnClass(Jackson2ObjectMapperBuilder.class) static class JacksonObjectMapperConfiguration { @Bean @Primary @ConditionalOnMissingBean ObjectMapper jacksonObjectMapper(Jackson2ObjectMapperBuilder builder) { // 通过Jackson2ObjectMapperBuilder构建出ObjectMapper return builder.createXmlMapper(false).build(); } }
五、解决方案落地
5.1、GET请求解决方案
application.yml配置 SpringBoot2.3.x以及更高的版本,springmvc增加了日期时间格式配置,既可以解决LocalDateTime类型参数解析,也可以解决Date类型参数解析
spring: mvc: date: yyyy-MM-dd time: HH:mm:ss date-time: yyyy-MM-dd HH:mm:ss
注解配置 SpringBoot针对LocalDateTime类型解析增加了@DateTimeFormatter注解,可以在请求参数中加上这个注解完成解析
@RestController public class LocalDateTimeController { @GetMapping("/resolveRequestParamDateTime") public void resolveRequestParamDateTime(@RequestParam @DateTimeFormat(pattern = "yyyy-MM-dd HH:mm:ss") LocalDateTime dateTime) { System.out.println("ok"); } @GetMapping("/resolvePathVariableDateTime/{dateTime}") public void resolvePathVariableDateTime(@PathVariable @DateTimeFormat(pattern = "yyyy-MM-dd HH:mm:ss") LocalDateTime dateTime) { System.out.println("ok"); } }
Java Config注入Bean
在Spring IOC容器中注入Converter,SpringBoot会自动将IOC容器中的Converter放到GenericConversionService中
@Configuration public class LocalDateTimeConfig { @Bean public Converter<String, LocalDateTime> stringToLocalDateTimeConverter() { return new Converter<String, LocalDateTime>() { @Override public LocalDateTime convert(String source) { return LocalDateTime.parse(source, DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")); } }; } @Bean public Converter<String, LocalDate> stringToLocalDateConverter() { return new Converter<String, LocalDate>() { @Override public LocalDate convert(String source) { return LocalDate.parse(source, DateTimeFormatter.ofPattern("yyyy-MM-dd")); } }; } @Bean public Converter<String, LocalTime> stringToLocalTimeConverter() { return new Converter<String, LocalTime>() { @Override public LocalTime convert(String source) { return LocalTime.parse(source, DateTimeFormatter.ofPattern("HH:mm:ss")); } }; } }
5.2、POST请求解决方案
注解配置 在实体类的字段上使用@JsonFormat注解配置格式,使用 @JsonSerialize注解配置序列化器,使用 @JsonDeserialize注解配置反序列化器
@RestController public class LocalDateTimeController { @PostMapping("/resolveBodyDateTime") public void resolveBodyDateTime(@RequestBody ResolveBody body) { System.out.println("ok"); } @Data private static class ResolveBody { @JsonSerialize(using = LocalDateTimeSerializer.class) @JsonDeserialize(using = LocalDateTimeDeserializer.class) @JsonFjsormat(pattern = "yyyy-MM-dd HH:mm:ss") private LocalDateTime dateTime; } }
Java Config注入Bean
在Spring IOC容器中注入Jackson2ObjectMapperBuilderCustomizer类型的Bean可以对Jackson进行自定义配置;也可以直接注入一个ObjectMapper进行替换
@Configuration public class LocalDateTimeConfig { @Bean public Jackson2ObjectMapperBuilderCustomizer jackson2ObjectMapperBuilderCustomizer() { return new Jackson2ObjectMapperBuilderCustomizer() { @Override public void customize(Jackson2ObjectMapperBuilder jacksonObjectMapperBuilder) { final JavaTimeModule javaTimeModule = new JavaTimeModule(); javaTimeModule.addSerializer(LocalDateTime.class, new LocalDateTimeSerializer(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"))); javaTimeModule.addSerializer(LocalDate.class, new LocalDateSerializer(DateTimeFormatter.ofPattern("yyyy-MM-dd"))); javaTimeModule.addSerializer(LocalTime.class, new LocalTimeSerializer(DateTimeFormatter.ofPattern("HH:mm:ss"))); javaTimeModule.addDeserializer(LocalDateTime.class, new LocalDateTimeDeserializer(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"))); javaTimeModule.addDeserializer(LocalDate.class, new LocalDateDeserializer(DateTimeFormatter.ofPattern("yyyy-MM-dd"))); javaTimeModule.addDeserializer(LocalTime.class, new LocalTimeDeserializer(DateTimeFormatter.ofPattern("HH:mm:ss"))); jacksonObjectMapperBuilder .modules(javaTimeModule) .featuresToDisable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES) .featuresToDisable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS) .simpleDateFormat("yyyy-MM-dd HH:mm:ss") .timeZone(TimeZone.getTimeZone("GMT+8")) .locale(Locale.CHINA); } }; } }
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