org.springframework.web.servlet.handler.AbstractHandlerExceptionResolver.logException Resolved

x33g5p2x  于2021-11-27 转载在 Spring  
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场景:

spring项目中无法访问到对应controller,查看日志,没有报错,只有warnring:

org.springframework.web.servlet.handler.AbstractHandlerExceptionResolver.logException Resolved [org.springframework.web.method.annotation.MethodArgumentTypeMismatchException:
 Failed to convert value of type 'java.lang.String' to required type 'java.util.Date'; nested exception is org.springframework.core.convert.ConversionFailedException: Failed to convert from type [java.lang.String] to type 
[@org.springframework.web.bind.annotation.RequestParam java.util.Date] for value '2019-06-21'; nested exception is java.lang.IllegalArgumentException]

直接来说就是字符串无法转为Date类型。

引起原因是大部分人使用Date格式作为controller接口的参数,导致springmvc无法将String转为Date,已知springmvc内置了一系列的转换,不过都是基本类型到包装类以及String到包装类,和List、Set、Map等。但是对类似String转Date还是无能为力的。

2种解决办法:

  1. 参数改为String类型,在后端处理String到Date的转换,而不是交给SpringMVC来处理。
  2. 写转换类实现org.springframework.core.convert.converter.Converter,并在SpringMVC中注册。

该Converter接口较为简单,代码略

<bean id="conversionService" class="org.springframework.context.support.ConversionServiceFactoryBean">
        <property name="converters">
            <set>
                <bean class="com.l.utils.StringToDateConverter"/>
            </set>
        </property>
    </bean>
    <mvc:annotation-driven conversion-service="conversionService"/>

如果是springboot项目:

@Bean
    public ConversionService conversionService() {
        FormattingConversionServiceFactoryBean factory = new FormattingConversionServiceFactoryBean();
        DateTimeFormatterRegistrar registrar = new DateTimeFormatterRegistrar();
        registrar.setDateFormatter(DateTimeFormatter.ofPattern("yyyy-MM-dd"));
        factory.setFormatterRegistrars(Collections.singleton(registrar));
        factory.afterPropertiesSet();
        return factory.getObject();
    }

原理:

springmvc默认已经提供了很多自动转换,查看org.springframework.context.support.ConversionServiceFactoryBean源码:

查看Converter接口:

@FunctionalInterface
public interface Converter<S, T> {
 
	/** * Convert the source object of type {@code S} to target type {@code T}. * @param source the source object to convert, which must be an instance of {@code S} (never {@code null}) * @return the converted object, which must be an instance of {@code T} (potentially {@code null}) * @throws IllegalArgumentException if the source cannot be converted to the desired target type */
	@Nullable
	T convert(S source);
 
}

已经注册的子类:

比如有从StringToBooleanConverter,就说明参数String到Boolean(参数以Boolean类型)是没有问题的!

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