SpringMVC 直接返回中文字符串时，出现乱码问号(?)的问题

<mvc:annotation-driven>
         <mvc:message-converters>
            <bean class="org.springframework.http.converter.StringHttpMessageConverter">
             <constructor-arg ref="utf8Charset"></constructor-arg>
            </bean>
         </mvc:message-converters>
    </mvc:annotation-driven>  
 <bean id="utf8Charset" class="java.nio.charset.Charset" factory-method="forName">
    <constructor-arg value="UTF-8"/>
 </bean>