spring mvc 删除返回字符串中值为null的字段

<bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">
        <property name="messageConverters">
            <list>
                <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
                    <property name="objectMapper">
                        <bean id="jacksonObjectMapper" class="com.fasterxml.jackson.databind.ObjectMapper">
                            <property name="dateFormat">
                                <bean class="java.text.SimpleDateFormat">
                                    <constructor-arg type="java.lang.String" value="yyyy-MM-dd HH:mm:ss" />
                                </bean>
                            </property>
                            <property name="serializationInclusion">
                                <util:constant static-field="com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL" />
                            </property>
                        </bean>
                    </property>
                    <property name="supportedMediaTypes">
                        <list>
                            <value>application/json;charset=UTF-8</value>
                        </list>
                    </property>
                </bean>
            </list>
        </property>
    </bean>