mybatis返回map类型数据空值字段不显示

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD SQL MAP Config 3.1//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<settings>
<setting name="callSettersOnNulls" value="true"/>
</settings>
</configuration>

<!-- spring和MyBatis完美整合，添加mybatis的配置映射文件 -->
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="dataSource" ref="dataSource"/>
<property name="configLocation" value="classpath:mybatis-configuration.xml"/>
<!-- 自动扫描mapping.xml文件 -->
<property name="mapperLocations" value="classpath:mapping/*.xml"></property>
</bean>

IFNULL(age,'') as age