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

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 {

    @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

@ControllerAdvice
public 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:

@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";


    @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;

@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
     */
    @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} 

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@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:

  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)。

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