mybatis返回map类型数据空值字段不显示的解决方案

IFNULL(rate,'') as rate

<?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>

public class EmptyStringIfNull implements TypeHandler<String> {
    @Override
    public String getResult(ResultSet rs, String columnName) throws SQLException {
     return (rs.getString(columnName) == null) ? "" : rs.getString(columnName); 
    }
    @Override
    public String getResult(ResultSet rs, int columnIndex) throws SQLException {
     return (rs.getString(columnIndex) == null) ? "" : rs.getString(columnIndex);
    }
    @Override
    public String getResult(CallableStatement cs, int columnIndex)   throws SQLException {
     return (cs.getString(columnIndex) == null) ? "" : cs.getString(columnIndex);
    }
    @Override
    public void setParameter(PreparedStatement ps, int arg1, String str, JdbcType jdbcType) throws SQLException { }}

<resultMap id="find" type="java.util.LinkedHashMap">
    <result property="name" column="name" />
    <result property="phone" column="phone" />
    <result property="rate" column="rate" typeHandler="com.mybatis.EmptyStringIfNull"/>
</resultMap>

@Bean
public SqlSessionFactory sqlSessionFactoryBean() throws Exception
{
    SqlSessionFactoryBean sqlSessionFactoryBean = new      SqlSessionFactoryBean();
    sqlSessionFactoryBean.setDataSource(dataSource());
    Configuration configuration = new .Configuration();
    configuration.setCallSettersOnNulls(true);//map返回空字段消失问题
    PageInterceptor pagePlugin = new PageInterceptor();
    JalorResultSetInterceptor jalorResultSetPlugin = new JalorResultSetInterceptor();
    ProgramInterceptor programPlugin = new ProgramInterceptor();
    //添加插件
    sqlSessionFactoryBean.setPlugins(new Interceptor[] {pagePlugin, jalorResultSetPlugin, programPlugin});
    sqlSessionFactoryBean.setConfiguration(configuration);
    return sqlSessionFactoryBean.getObject();
}