springMVC3.2 多视图解析器 java.lang.String cannot be cast to org.springframework.http.MediaType

SpringMVC 3.2 org.springframework.web.servlet.view.ContentNegotiatingViewResolver 配置如下mediaType报错
<property name="mediaTypes">
<map>
<entry key="pdf" value="application/pdf"/>
<entry key="html" value="text/html"/>
<entry key="json" value="application/json"/>
</map>
</property>
换成

<bean class="org.springframework.web.servlet.view.ContentNegotiatingViewResolver">
<property name="contentNegotiationManager">
<bean class="org.springframework.web.accept.ContentNegotiationManager">
<constructor-arg>
<list>
<!-- These are evaluated in order -->
<!-- Is there a media type based on suffix? -->
<bean                  class="org.springframework.web.accept.PathExtensionContentNegotiationStrategy">
<constructor-arg>
<map>
<entry key="html" value="text/html" />
<entry key="json" value="application/json" />
<entry key="pdf" value="application/pdf" />
</map>
</constructor-arg>
</bean>
<!-- Else use request header -->
<bean
class="org.springframework.web.accept.HeaderContentNegotiationStrategy">

</bean>
</list>
</constructor-arg>
</bean>
</property>
</bean>