mvc:resources与conversionService报错问题

最近在代码中加了mvc资源的注册

    <mvc:resources mapping="/assets/**" location="assets/"/>

而后因为时间问题，又加了spring转换器的bean

 <bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">
        <property name="messageConverters">
            <list>
                <ref bean="mappingFastJsonHttpMessageConverter"/> <!-- JSON转换器 -->
            </list>
        </property>
        <property name="webBindingInitializer">
            <bean class="org.springframework.web.bind.support.ConfigurableWebBindingInitializer">
                <property name="conversionService" ref="conversionService" />
            </bean>
        </property>
    </bean>

    <!--格式转换-->
    <bean id="conversionService" class="org.springframework.format.support.DefaultFormattingConversionService"/>

当日志格式为DEBUG的时候，看到了有报错

org.springframework.core.convert.ConversionFailedException: Failed to convert from type [java.util.ArrayList<?>] to type [java.util.List<org.springframework.core.io.Resource>] for value '[assets/]'; nested exception is org.springframework.core.convert.ConverterNotFoundException: No converter found capable of converting from type [java.util.ArrayList<?>] to type [org.springframework.core.io.Resource]
    at org.springframework.core.convert.support.ConversionUtils.invokeConverter(ConversionUtils.java:41)
    at org.springframework.core.convert.support.GenericConversionService.convert(GenericConversionService.java:192)
    at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:173)
    at org.springframework.beans.AbstractNestablePropertyAccessor.convertIfNecessary(AbstractNestablePropertyAccessor.java:576)
    at org.springframework.beans.AbstractNestablePropertyAccessor.convertForProperty(AbstractNestablePropertyAccessor.java:603)
    at org.springframework.beans.BeanWrapperImpl.convertForProperty(BeanWrapperImpl.java:204)

多次dubug后发现，如果有注册mvc:resources，同时配置文件中又有id为"conversionService"的bean，就会报错。

解决方法就是将conversionService的bean id修改了。很奇怪的问题。