Mybatis无法获取带有下划线前缀的字段的值问题

<configuration>
    <!-- 全局配置 -->
    <settings>
        <!--允许 JDBC 支持自动生成主键-->
        <setting name="useGeneratedKeys" value="false"/>
       <!--是否开启自动驼峰命名规则（camel case）映射，即从经典数据库列名 A_COLUMN 到经典
Java 属性名 aColumn 的类似映射。 -->
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>
</configuration>

<!-- 是否开启自动驼峰命名规则（camel case）映射， -->
<setting name="mapUnderscoreToCamelCase" value="true"/>

//开启驼峰映射
        bean.getObject().getConfiguration().setMapUnderscoreToCamelCase(true);

    public class demo {  
      private String user_name;  
      private Striing pass_word;             
      public String getPass_word(){  
           return pass_word;  
      }  
      public void setPass_word(String pass_word){  
           this.pass_word=pass_word;  
      }       
    } 

select user_name,pass_word from demo;

select user_name as username,pass_word as password from demo;

    public void setUsernaem(String user_name){  
          this.user_name=user_name;  
     }  
     public void setPassword(String pass_word){  
          this.pass_word=pass_word;  
     }