mybatis的多表查询映射问题

mybatis的多表映射：

　　表字段映射实体的几种情况：

　　 单表查询

　　　　第一种。起别名：  起的别名一定是对应的实体字段名。

　　　　　　

SELECT
    t_p.param_id paramId, 
    t_p.station_id stationId,
    t_p.station_name stationName,
    t_p.pump_id pumpId,
    t_p.vibrate vibrate,
    t_p.temperature temperature,
    t_p.report_time reportTimeP   
FROM
    dbo.tb_param AS t_p
    

　　　　第二种：mybatis的驼峰命名对应

　　　　

<configuration>
    <settings>  
        <setting name="mapUnderscoreToCamelCase" value="true" />  
    </settings>
</configuration>

这种适合param_id   对应  实体中的  paramId

　　 多表查询  

　　

<!--泵机基本参数-->
    <resultMap type="PLCParam" id="commentResult">
        <id property="paramId" column="param_id"/>
        <result property="stationId" column="station_id"/>
        <result property="stationName" column="station_name"/>
        <result property="pumpId" column="pump_id"/>
        <result property="vibrate" column="vibrate"/>
        <result property="temperature" column="temperature"/>
        <result property="reportTime" column="report_time" jdbcType="TIMESTAMP"/>
        <association property="electricity"  resultMap="plcelectricityResult"/>
        <association property="voltage"  resultMap="plcvoltageResult"/>
        <association property="flow"  resultMap="plcflowResult"/>
        <association property="status"  resultMap="plcstatusResult"/>
    </resultMap>
    <!--电流表-->
    <resultMap type="PLCElectricity" id="plcelectricityResult">
        <id property="electriId" column="electri_id"/>
        <result property="stationId" column="station_id"/>
        <result property="stationName" column="station_name"/>
        <result property="pumpId" column="pump_id"/>
        <result property="electriOne" column="electri_one"/>
        <result property="electriTwo" column="electri_two"/>
        <result property="electriThree" column="electri_three"/>
        <result property="reportTimeE" column="report_time" jdbcType="TIMESTAMP"/>
    </resultMap>
    <!--电压表-->
    <resultMap type="PLCVoltage" id="plcvoltageResult">
        <id property="voltageId" column="voltage_id"/>
        <result property="stationId" column="station_id"/>
        <result property="stationName" column="station_name"/>
        <result property="pumpId" column="pump_id"/>
        <result property="voltageOne" column="voltage_one"/>
        <result property="voltageTwo" column="voltage_two"/>
        <result property="voltageThree" column="voltage_three"/>
        <result property="reportTimeV" column="report_time"/>
    </resultMap>
    <!--flow流量表-->
    <resultMap type="PLCFlow" id="plcflowResult">
        <id property="flowId" column="flow_id"/>
        <result property="stationId" column="station_id"/>
        <result property="stationName" column="station_name"/>
        <result property="pumpId" column="pump_id"/>
        <result property="inputFlow" column="input_flow"/>
        <result property="outputFlow" column="output_flow"/>
        <result property="reportTimeF" column="report_time" jdbcType="TIMESTAMP"/>
    </resultMap>
    <!--状态表-->
    <resultMap type="PLCStatus" id="plcstatusResult">
        <id property="paramId" column="param_id"/>
        <result property="stationId" column="station_id"/>
        <result property="stationName" column="station_name"/>
        <result property="pumpId" column="pump_id"/>
        <result property="status" column="status"/>
        <result property="lastUpdateTime" column="last_update_time" jdbcType="TIMESTAMP"/>
    </resultMap>

    <!--泵机的基本参数-->
    <select id="queryPlcParam" resultMap="commentResult">
      SELECT
            t_p.param_id,/*参数表id*/
            t_p.station_id,/*泵站id*/
            t_p.station_name,/*泵站名称*/
            t_p.pump_id ,/*泵机id*/
            t_p.vibrate,/*泵机振动*/
            t_p.temperature,/*泵机温度*/
            t_p.report_time,/*参数表上报时间*/
            t_f.input_flow,/*进口流量*/
            t_f.output_flow,/*出口流量*/
            t_f.report_time,/*流量表上报时间*/
            t_s.status,/*泵机状态 0:启动，1：停止，2：故障*/
            t_s.last_update_time,/*最后更新时间*/
            t_v.voltage_one,/*电压数据1*/
            t_v.voltage_two,/*电压数据2*/
            t_v.voltage_three,/*电压数据3*/
            t_v.report_time,/*电压上报时间*/
            t_e.electri_one,/*电流数据1*/
            t_e.electri_two,/*电流数据2*/
            t_e.electri_three,/*电流数据3*/
            t_e.report_time/*电流上报时间*/
      FROM
        dbo.tb_param AS t_p
            LEFT JOIN dbo.tb_flow AS t_f ON t_f.station_id = t_p.station_id
            AND t_f.pump_id = t_p.pump_id
            LEFT JOIN dbo.tb_status AS t_s ON t_s.station_id = t_p.station_id
            AND t_s.pump_id = t_p.pump_id
            LEFT JOIN dbo.tb_voltage AS t_v ON t_v.station_id = t_p.station_id
            AND t_v.pump_id = t_p.pump_id
            LEFT JOIN dbo.tb_electricity AS t_e ON t_e.pump_id = t_p.pump_id
            AND t_e.station_id = t_p.station_id

    </select>

　　使用resultMap接收不用指定列别名。如果指定列别名，属于驼峰命名格式的字段映射为空

　　实体如下：

　　

 /**自动增长ID，数据表主键*/
    private int paramId;
    /**泵站编号*/
    private int stationId;
    /**泵站name*/
    private String stationName;
    /**泵机id*/
    private int pumpId;
    /**泵机振动 */
    private String vibrate;
    /**泵机温度 */
    private String temperature;
    /**上报时间*/
    private Date reportTime;

    private PLCElectricity electricity;

    private PLCFlow flow;

    private PLCStatus status;

    private PLCVoltage voltage;