Spring中使用LocalDateTime、LocalDate等参数作为入参

时间:2021-05-20

0x0 背景

项目中使用LocalDateTime系列作为dto中时间的类型,但是spring收到参数后总报错,为了全局配置时间类型转换,尝试了如下3中方法。

注:本文基于Springboot2.0测试,如果无法生效可能是spring版本较低导致的。PS:如果你的Controller中的LocalDate类型的参数啥注解(RequestParam、PathVariable等)都没加,也是会出错的,因为默认情况下,解析这种参数使用ModelAttributeMethodProcessor进行处理,而这个处理器要通过反射实例化一个对象出来,然后再对对象中的各个参数进行convert,但是LocalDate类没有构造函数,无法反射实例化因此会报错!!!

0x1 当LocalDateTime作为RequestParam或者PathVariable时

这种情况要和时间作为Json字符串时区别对待,因为前端json转后端pojo底层使用的是Json序列化Jackson工具(HttpMessgeConverter);而时间字符串作为普通请求参数传入时,转换用的是Converter,两者有区别哦。
在这种情况下,有如下几种方案:

1. 使用Converter

import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.core.convert.converter.Converter;import org.springframework.http.converter.HttpMessageConverter;import java.time.LocalDate;import java.time.LocalDateTime;import java.time.format.DateTimeFormatter;@Configurationpublic class DateConfig { @Bean public Converter<String, LocalDate> localDateConverter() { return new Converter<>() { @Override public LocalDate convert(String source) { return LocalDate.parse(source, DateTimeFormatter.ofPattern("yyyy-MM-dd")); } }; } @Bean public Converter<String, LocalDateTime> localDateTimeConverter() { return new Converter<>() { @Override public LocalDateTime convert(String source) { return LocalDateTime.parse(source, DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")); } }; }}

以上两个bean会注入到spring mvc的参数解析器(好像叫做ParameterConversionService),当传入的字符串要转为LocalDateTime类时,spring会调用该Converter对这个入参进行转换。

2. 使用ControllerAdvice配合initBinder

@ControllerAdvicepublic class GlobalExceptionHandler { @InitBinder protected void initBinder(WebDataBinder binder) { binder.registerCustomEditor(LocalDate.class, new PropertyEditorSupport() { @Override public void setAsText(String text) throws IllegalArgumentException { setValue(LocalDate.parse(text, DateTimeFormatter.ofPattern("yyyy-MM-dd"))); } }); binder.registerCustomEditor(LocalDateTime.class, new PropertyEditorSupport() { @Override public void setAsText(String text) throws IllegalArgumentException { setValue(LocalDateTime.parse(text, DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"))); } }); binder.registerCustomEditor(LocalTime.class, new PropertyEditorSupport() { @Override public void setAsText(String text) throws IllegalArgumentException { setValue(LocalTime.parse(text, DateTimeFormatter.ofPattern("HH:mm:ss"))); } }); }}

从名字就可以看出来,这是在controller做环切(这里面还可以全局异常捕获),在参数进入handler之前进行转换;转换为我们相应的对象。

0x2 当LocalDateTime作为Json形式传入

这种情况下,如同上文描述,要利用Jackson的json序列化和反序列化来做:

@Configurationpublic class JacksonConfig { /** 默认日期时间格式 */ public static final String DEFAULT_DATE_TIME_FORMAT = "yyyy-MM-dd HH:mm:ss"; /** 默认日期格式 */ public static final String DEFAULT_DATE_FORMAT = "yyyy-MM-dd"; /** 默认时间格式 */ public static final String DEFAULT_TIME_FORMAT = "HH:mm:ss"; @Bean public ObjectMapper objectMapper(){ ObjectMapper objectMapper = new ObjectMapper();// objectMapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);// objectMapper.disable(DeserializationFeature.ADJUST_DATES_TO_CONTEXT_TIME_ZONE); JavaTimeModule javaTimeModule = new JavaTimeModule(); javaTimeModule.addSerializer(LocalDateTime.class,new LocalDateTimeSerializer(DateTimeFormatter.ofPattern(DEFAULT_DATE_TIME_FORMAT))); javaTimeModule.addSerializer(LocalDate.class,new LocalDateSerializer(DateTimeFormatter.ofPattern(DEFAULT_DATE_FORMAT))); javaTimeModule.addSerializer(LocalTime.class,new LocalTimeSerializer(DateTimeFormatter.ofPattern(DEFAULT_TIME_FORMAT))); javaTimeModule.addDeserializer(LocalDateTime.class,new LocalDateTimeDeserializer(DateTimeFormatter.ofPattern(DEFAULT_DATE_TIME_FORMAT))); javaTimeModule.addDeserializer(LocalDate.class,new LocalDateDeserializer(DateTimeFormatter.ofPattern(DEFAULT_DATE_FORMAT))); javaTimeModule.addDeserializer(LocalTime.class,new LocalTimeDeserializer(DateTimeFormatter.ofPattern(DEFAULT_TIME_FORMAT))); objectMapper.registerModule(javaTimeModule).registerModule(new ParameterNamesModule()); return objectMapper; }}

0x3 来个完整的配置吧

package com.fly.hi.common.config;import com.fasterxml.jackson.core.JsonGenerator;import com.fasterxml.jackson.core.JsonParser;import com.fasterxml.jackson.core.JsonProcessingException;import com.fasterxml.jackson.databind.*;import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;import com.fasterxml.jackson.datatype.jsr310.deser.LocalDateDeserializer;import com.fasterxml.jackson.datatype.jsr310.deser.LocalDateTimeDeserializer;import com.fasterxml.jackson.datatype.jsr310.deser.LocalTimeDeserializer;import com.fasterxml.jackson.datatype.jsr310.ser.LocalDateSerializer;import com.fasterxml.jackson.datatype.jsr310.ser.LocalDateTimeSerializer;import com.fasterxml.jackson.datatype.jsr310.ser.LocalTimeSerializer;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.core.convert.converter.Converter;import java.io.IOException;import java.text.ParseException;import java.text.SimpleDateFormat;import java.time.LocalDate;import java.time.LocalDateTime;import java.time.LocalTime;import java.time.format.DateTimeFormatter;import java.util.Date;@Configurationpublic class DateConfig { /** 默认日期时间格式 */ public static final String DEFAULT_DATE_TIME_FORMAT = "yyyy-MM-dd HH:mm:ss"; /** 默认日期格式 */ public static final String DEFAULT_DATE_FORMAT = "yyyy-MM-dd"; /** 默认时间格式 */ public static final String DEFAULT_TIME_FORMAT = "HH:mm:ss"; /** * LocalDate转换器,用于转换RequestParam和PathVariable参数 */ @Bean public Converter<String, LocalDate> localDateConverter() { return new Converter<>() { @Override public LocalDate convert(String source) { return LocalDate.parse(source, DateTimeFormatter.ofPattern(DEFAULT_DATE_FORMAT)); } }; } /** * LocalDateTime转换器,用于转换RequestParam和PathVariable参数 */ @Bean public Converter<String, LocalDateTime> localDateTimeConverter() { return new Converter<>() { @Override public LocalDateTime convert(String source) { return LocalDateTime.parse(source, DateTimeFormatter.ofPattern(DEFAULT_DATE_TIME_FORMAT)); } }; } /** * LocalTime转换器,用于转换RequestParam和PathVariable参数 */ @Bean public Converter<String, LocalTime> localTimeConverter() { return new Converter<>() { @Override public LocalTime convert(String source) { return LocalTime.parse(source, DateTimeFormatter.ofPattern(DEFAULT_TIME_FORMAT)); } }; } /** * Date转换器,用于转换RequestParam和PathVariable参数 */ @Bean public Converter<String, Date> dateConverter() { return new Converter<>() { @Override public Date convert(String source) { SimpleDateFormat format = new SimpleDateFormat(DEFAULT_DATE_TIME_FORMAT); try { return format.parse(source); } catch (ParseException e) { throw new RuntimeException(e); } } }; } /** * Json序列化和反序列化转换器,用于转换Post请求体中的json以及将我们的对象序列化为返回响应的json */ @Bean public ObjectMapper objectMapper(){ ObjectMapper objectMapper = new ObjectMapper(); objectMapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS); objectMapper.disable(DeserializationFeature.ADJUST_DATES_TO_CONTEXT_TIME_ZONE); //LocalDateTime系列序列化和反序列化模块,继承自jsr310,我们在这里修改了日期格式 JavaTimeModule javaTimeModule = new JavaTimeModule(); javaTimeModule.addSerializer(LocalDateTime.class,new LocalDateTimeSerializer(DateTimeFormatter.ofPattern(DEFAULT_DATE_TIME_FORMAT))); javaTimeModule.addSerializer(LocalDate.class,new LocalDateSerializer(DateTimeFormatter.ofPattern(DEFAULT_DATE_FORMAT))); javaTimeModule.addSerializer(LocalTime.class,new LocalTimeSerializer(DateTimeFormatter.ofPattern(DEFAULT_TIME_FORMAT))); javaTimeModule.addDeserializer(LocalDateTime.class,new LocalDateTimeDeserializer(DateTimeFormatter.ofPattern(DEFAULT_DATE_TIME_FORMAT))); javaTimeModule.addDeserializer(LocalDate.class,new LocalDateDeserializer(DateTimeFormatter.ofPattern(DEFAULT_DATE_FORMAT))); javaTimeModule.addDeserializer(LocalTime.class,new LocalTimeDeserializer(DateTimeFormatter.ofPattern(DEFAULT_TIME_FORMAT))); //Date序列化和反序列化 javaTimeModule.addSerializer(Date.class, new JsonSerializer<>() { @Override public void serialize(Date date, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException { SimpleDateFormat formatter = new SimpleDateFormat(DEFAULT_DATE_TIME_FORMAT); String formattedDate = formatter.format(date); jsonGenerator.writeString(formattedDate); } }); javaTimeModule.addDeserializer(Date.class, new JsonDeserializer<>() { @Override public Date deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException, JsonProcessingException { SimpleDateFormat format = new SimpleDateFormat(DEFAULT_DATE_TIME_FORMAT); String date = jsonParser.getText(); try { return format.parse(date); } catch (ParseException e) { throw new RuntimeException(e); } } }); objectMapper.registerModule(javaTimeModule); return objectMapper; }}

0x4 深入研究SpringMVC数据绑定过程

接下来进入debug模式,看看mvc是如何将我们request中的参数绑定到我们controller层方法入参的:

写一个简单controller,下个断点看看方法调用栈:

@GetMapping("/getDate") public LocalDateTime getDate(@RequestParam LocalDate date, @RequestParam LocalDateTime dateTime, @RequestParam Date originalDate) { System.out.println(date); System.out.println(dateTime); System.out.println(originalDate); return LocalDateTime.now(); }

断住以后,我们看下方法调用栈中一些关键方法:

//进入DispatcherServletdoService:942, DispatcherServlet//处理请求doDispatch:1038, DispatcherServlet//生成调用链(前处理、实际调用方法、后处理)handle:87, AbstractHandlerMethodAdapter//反射获取到实际调用方法,准备开始调用invokeHandlerMethod:895, RequestMappingHandlerAdapterinvokeAndHandle:102, ServletInvocableHandlerMethod//这里是关键,参数从这里开始获取到invokeForRequest:142, InvocableHandlerMethoddoInvoke:215, InvocableHandlerMethod//这个是Java reflect调用,因此一定是在这之前获取到的参数invoke:566, Method

根据上述分析,发现invokeForRequest:142, InvocableHandlerMethod这里的代码是用来拿到实际参数的:

@Nullable public Object invokeForRequest(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer, Object... providedArgs) throws Exception { //这个方法是获取参数的,在这里下个断 Object[] args = getMethodArgumentValues(request, mavContainer, providedArgs); if (logger.isTraceEnabled()) { logger.trace("Arguments: " + Arrays.toString(args)); } //这里开始调用方法 return doInvoke(args); }

进入这个方法看看是什么操作:

protected Object[] getMethodArgumentValues(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer, Object... providedArgs) throws Exception { //获取方法参数数组,包含了入参信息,比如类型、泛型等等 MethodParameter[] parameters = getMethodParameters(); //这个用来存放一会从request parameter转换的参数 Object[] args = new Object[parameters.length]; for (int i = 0; i < parameters.length; i++) { MethodParameter parameter = parameters[i]; parameter.initParameterNameDiscovery(this.parameterNameDiscoverer); //这里看起来没啥卵用(providedArgs为空) args[i] = resolveProvidedArgument(parameter, providedArgs); //这里开始获取到方法实际调用的参数,步进 if (this.argumentResolvers.supportsParameter(parameter)) { //从名字就看出来:参数解析器解析参数 args[i] = this.argumentResolvers.resolveArgument(parameter, mavContainer, request, this.dataBinderFactory); continue; } } return args; }

进入resolveArgument看看:

public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer, NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception { //根据方法入参,获取对应的解析器 HandlerMethodArgumentResolver resolver = getArgumentResolver(parameter); //开始解析参数(把请求中的parameter转为方法的入参) return resolver.resolveArgument(parameter, mavContainer, webRequest, binderFactory); }

这里根据参数获取相应的参数解析器,看看内部如何获取的:

//遍历,调用supportParameter方法,跟进看看 for (HandlerMethodArgumentResolver methodArgumentResolver : this.argumentResolvers) { if (methodArgumentResolver.supportsParameter(parameter)) { result = methodArgumentResolver; this.argumentResolverCache.put(parameter, result); break; } }

这里,遍历参数解析器,查找有没有适合的解析器!那么,有哪些参数解析器呢(我测试的时候有26个)???我列出几个重要的看看,是不是很眼熟!!!

{RequestParamMethodArgumentResolver@7686} {PathVariableMethodArgumentResolver@8359} {RequestResponseBodyMethodProcessor@8366} {RequestPartMethodArgumentResolver@8367}

我们进入最常用的一个解析器看看他的supportsParameter方法,发现就是通过参数注解来获取相应的解析器的。

public boolean supportsParameter(MethodParameter parameter) { //如果参数拥有注解@RequestParam,则走这个分支(知道为什么上文要对RequestParam和Json两种数据区别对待了把) if (parameter.hasParameterAnnotation(RequestParam.class)) { //这个似乎是对Optional类型的参数进行处理的 if (Map.class.isAssignableFrom(parameter.nestedIfOptional().getNestedParameterType())) { RequestParam requestParam = parameter.getParameterAnnotation(RequestParam.class); return (requestParam != null && StringUtils.hasText(requestParam.name())); } else { return true; } } //...... }

也就是说,对于@RequestParam和@RequestBody以及@PathVariable注解的参数,SpringMVC会使用不通的参数解析器进行数据绑定!

那么,这三种解析器分别使用什么Converter解析参数呢?我们分别进入三种解析器看一看:

首先看下RequestParamMethodArgumentResolver发现内部使用WebDataBinder进行数据绑定,底层使用的是ConversionService (也就是我们的Converter注入的地方)

WebDataBinder binder = binderFactory.createBinder(webRequest, null, namedValueInfo.name);//通过DataBinder进行数据绑定的arg = binder.convertIfNecessary(arg, parameter.getParameterType(), parameter); //跟进convertIfNecessary() public <T> T convertIfNecessary(@Nullable Object value, @Nullable Class<T> requiredType, @Nullable MethodParameter methodParam) throws TypeMismatchException { return getTypeConverter().convertIfNecessary(value, requiredType, methodParam); } //继续跟进,看到了把 ConversionService conversionService = this.propertyEditorRegistry.getConversionService(); if (editor == null && conversionService != null && newValue != null && typeDescriptor != null) { TypeDescriptor sourceTypeDesc = TypeDescriptor.forObject(newValue); if (conversionService.canConvert(sourceTypeDesc, typeDescriptor)) { try { return (T) conversionService.convert(newValue, sourceTypeDesc, typeDescriptor); } catch (ConversionFailedException ex) { // fallback to default conversion logic below conversionAttemptEx = ex; } } }

然后看下RequestResponseBodyMethodProcessor发现使用的转换器是HttpMessageConverter类型的:

//resolveArgument方法内部调用下面进行参数解析Object arg = readWithMessageConverters(webRequest, parameter, parameter.getNestedGenericParameterType());//step into readWithMessageConverters(),我们看到这里的Converter是HttpMessageConverter 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); 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; } }

最后看下PathVariableMethodArgumentResolver发现 和RequestParam走的执行路径一致(二者都是继承自AbstractNamedValueMethodArgumentResolver解析器),因此代码就不贴了。

0xFF总结

如果要转换request传来的参数到我们指定的类型,根据入参注解要进行区分:

如果是RequestBody,那么通过配置ObjectMapper(这个玩意儿会注入到Jackson的HttpMessagConverter里面,即MappingJackson2HttpMessageConverter中)来实现Json格式数据的序列化和反序列化;
如果是RequestParam或者PathVariable类型的参数,通过配置Converter实现参数转换(这些Converter会注入到ConversionService中)。

以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持。

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