Spring Boot使用LocalDateTime、LocalDate作为入参

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;@Configuration
public class DateConfig {@Beanpublic Converter<String, LocalDate> localDateConverter() {return new Converter<>() {@Overridepublic LocalDate convert(String source) {return LocalDate.parse(source, DateTimeFormatter.ofPattern("yyyy-MM-dd"));}};}@Beanpublic Converter<String, LocalDateTime> localDateTimeConverter() {return new Converter<>() {@Overridepublic 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。

注意：关于自定义的参数转换器 Converter，这里遇到了一个坑，再这里详细记录下，本来想法是为了代码精简，将上面匿名内部类的写法精简成lambda表达式的方式：

    @Bean@ConditionalOnBean(name = "requestMappingHandlerAdapter")public Converter<String, LocalDate> localDateConverter() {return source -> LocalDate.parse(source, DateTimeFormatter.ofPattern(DEFAULT_DATE_FORMAT));}

当我再次启动项目时却出现了异常：

Caused by: java.lang.IllegalArgumentException: Unable to determine source type <S> and target type <T> for your Converter [com.example.demo126.config.MappingConverterAdapter$$Lambda$522/817994751]; does the class parameterize those types?

 百思不得其解，在查阅了资料才得知一二。

web项目启动注册requestMappingHandlerAdapter的时候会初始化WebBindingInitializer

adapter.setWebBindingInitializer(getConfigurableWebBindingInitializer());

而ConfigurableWebBindingInitializer需要FormattingConversionService, 而FormattingConversionService会将所有的Converter添加进来，添加的时候需要获取泛型信息：

@Override
public void addFormatters(FormatterRegistry registry) {for (Converter<?, ?> converter : getBeansOfType(Converter.class)) {registry.addConverter(converter);}for (GenericConverter converter : getBeansOfType(GenericConverter.class)) {registry.addConverter(converter);}for (Formatter<?> formatter : getBeansOfType(Formatter.class)) {registry.addFormatter(formatter);}
}

添加Converter.class 一般是通过接口获取两个泛型的具体类型

public ResolvableType as(Class<?> type) {if (this == NONE) {return NONE;}Class<?> resolved = resolve();if (resolved == null || resolved == type) {return this;}for (ResolvableType interfaceType : getInterfaces()) {ResolvableType interfaceAsType = interfaceType.as(type);if (interfaceAsType != NONE) {return interfaceAsType;}}return getSuperType().as(type);
}

Lambda表达式的接口是Converter，并不能得到具体的类型，在窥探了SpringMVC源码后才得知原来如此，既然指导了原因，那解决办法：

• 最简单的方法就是不适用Lambda表达式，还是老老实实的使用匿名内部类，这样就不会存在上述问题

• 或者就是等requestMappingHandlerAdapterbean注册完成之后再添加自己的converter就不会注册到FormattingConversionService中

@Bean
@ConditionalOnBean(name = "requestMappingHandlerAdapter")
public Converter<String, LocalDateTime> localDateTimeConverter() {return source -> LocalDateTime.parse(source, DateTimeUtils.DEFAULT_FORMATTER);
}

还可以对前端传递的string进行正则匹配，如yyyy-MM-dd HH:mm:ss、yyyy-MM-dd、 HH:mm:ss等，进行匹配。以适应多种场景。

@Component
public class DateConverter implements Converter<String, Date> {@Overridepublic Date convert(String value) {/*** 可对value进行正则匹配，支持日期、时间等多种类型转换* 这里我偷个懒，在匹配Date日期格式时直接使用了 hutool 为我们已经写好的解析工具类，这里就不重复造轮子了* cn.hutool.core.date.DateUtil* @param value* @return*/return DateUtil.parse(value.trim());}
}

 注：这里偷个懒，在匹配Date日期格式时直接使用了 hutool 已经写好的解析工具类，这里就不重复造轮子了，下面的方法同样使用了该工具类，想要在自己的项目中使用该工具类也很简单，在项目pom文件中引入hutool的依赖就可以了。

2. 使用ControllerAdvice配合initBinder

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

@Configuration
public 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";@Beanpublic 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 当LocalDateTime作为Json形式传入 

import cn.hutool.core.date.DatePattern;
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.boot.autoconfigure.jackson.Jackson2ObjectMapperBuilderCustomizer;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.time.format.DateTimeFormatter;
import java.util.Locale;
import java.util.TimeZone;@Configuration
public class DateConfig {@Beanpublic Jackson2ObjectMapperBuilderCustomizer customizer() {return builder -> {builder.locale(Locale.CHINA);builder.timeZone(TimeZone.getTimeZone("GMT+8:00"));builder.simpleDateFormat(DatePattern.NORM_DATETIME_PATTERN);JavaTimeModule javaTimeModule = new JavaTimeModule();javaTimeModule.addSerializer(LocalDateTime.class, new LocalDateTimeSerializer(DateTimeFormatter.ofPattern(DatePattern.NORM_DATETIME_PATTERN)));javaTimeModule.addSerializer(LocalDate.class, new LocalDateSerializer(DateTimeFormatter.ofPattern(DatePattern.NORM_DATE_PATTERN)));javaTimeModule.addSerializer(LocalTime.class, new LocalTimeSerializer(DateTimeFormatter.ofPattern(DatePattern.NORM_TIME_PATTERN)));javaTimeModule.addDeserializer(LocalDateTime.class, new LocalDateTimeDeserializer(DateTimeFormatter.ofPattern(DatePattern.NORM_DATETIME_PATTERN)));javaTimeModule.addDeserializer(LocalDate.class, new LocalDateDeserializer(DateTimeFormatter.ofPattern(DatePattern.NORM_DATE_PATTERN)));javaTimeModule.addDeserializer(LocalTime.class, new LocalTimeDeserializer(DateTimeFormatter.ofPattern(DatePattern.NORM_TIME_PATTERN)));builder.modules(javaTimeModule);};}}

 0x4 来个完整的配置

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;@Configuration
public 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*/@Beanpublic Converter<String, LocalDate> localDateConverter() {return new Converter<>() {@Overridepublic 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*/@Beanpublic Converter<String, LocalDateTime> localDateTimeConverter() {return new Converter<>() {@Overridepublic 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*/@Beanpublic Converter<String, LocalTime> localTimeConverter() {return new Converter<>() {@Overridepublic 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*/@Beanpublic Converter<String, Date> dateConverter() {return new Converter<>() {@Overridepublic 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*/@Beanpublic 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<>() {@Overridepublic 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<>() {@Overridepublic 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;}
}

 0x5 深入研究SpringMVC数据绑定过程

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，看下方法调用栈中一些关键方法：

//进入DispatcherServlet
doService: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, RequestMappingHandlerAdapter
invokeAndHandle:102, ServletInvocableHandlerMethod
//这里是关键，参数从这里开始获取到
invokeForRequest:142, InvocableHandlerMethod
doInvoke: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} 

进入最常用的一个解析器看看它的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会使用不同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？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 belowconversionAttemptEx = 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传来的参数到指定的类型，根据入参注解要进行区分：

1. 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；

2. 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）。