MyBatis中TypeHandler的使用教程详解

//此接口作用是用于指定jdbc与java的数据类型间对应关系处理。
public interface TypeHandler<T> {
  // 保存操作，数据入库之前时数据处理
  void setParameter(PreparedStatement ps, int i, T parameter, JdbcType jdbcType) throws SQLException;
  //下面三个则是，从数据库加载数据后，vo对象封装前的数据处理
  T getResult(ResultSet rs, String columnName) throws SQLException;
  T getResult(ResultSet rs, int columnIndex) throws SQLException;
  T getResult(CallableStatement cs, int columnIndex) throws SQLException;
}

public class JsonIntegerTypeHandler extends BaseTypeHandler<Integer> {
    private static final ObjectMapper mapper = new ObjectMapper();

    @Override
    public void setNonNullParameter(PreparedStatement ps, int i, Integer parameter, JdbcType jdbcType) throws SQLException {
        ps.setString(i, toJson(parameter));
    }

    @Override
    public Integer getNullableResult(ResultSet rs, String columnName) throws SQLException {
        return this.toObject(rs.getString(columnName));
    }

    @Override
    public Integer getNullableResult(ResultSet rs, int columnIndex) throws SQLException {
        return this.toObject(rs.getString(columnIndex));
    }

    @Override
    public Integer getNullableResult(CallableStatement cs, int columnIndex) throws SQLException {
        return this.toObject(cs.getString(columnIndex));
    }

    private String toJson(Integer params) {
        try {
            String copyObject = IotDbUtils.copyObject(params);
            return copyObject;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return "";
    }

    private Integer toObject(String content) {
        if (content != null && !content.isEmpty()) {
            try {
                System.out.println("1111111111111"+content);
                return (Integer) mapper.readValue(content, Integer.class);
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        } else {
            return null;
        }
    }
}

    <resultMap id="DmpDeviceReportResult" type="com.chinaunicom.iotdb.domain.DmpDeviceReportInformation" >
        <result column="Time" property="timestamp" />

        <result column="type" jdbcType="INTEGER"
                property="type" typeHandler="com.chinaunicom.iotdb.handler.JsonIntegerTypeHandler"/>
        

    </resultMap>

  <select id="listDeviceReportInformation" resultMap="DmpDeviceReportResult">
        select trace_id, imei, topic, information, interaction_time,type
        from dmp_device_report_information
        where imei = #{serialNumber}
        <if test="beginTime != null and endTime != null">
            and interaction_time between #{beginTime} and #{endTime}
        </if>
        <if test="traceId != null and traceId != ''">
            and trace_id = #{traceId}
        </if>
        limit #{pageSize}  offset #{pageNum}
    </select>

<insert id="add" parameterType="com.chinaunicom.iotdb.domain.DmpDeviceReportInformation">
        INSERT INTO root.device.dmp_device_report_information
        <trim prefix="(" suffix=")" suffixOverrides=",">
            <if test="null != type ">
                type,
            </if>
            <if test="null != traceId and '' != traceId">
                trace_id,
            </if>
            <if test="null != imei and '' != imei">
                imei,
            </if>
            <if test="null != topic and '' != topic">
                topic,
            </if>
            <if test="null != information and '' != information">
                information,
            </if>
            <if test="null != interactionTime  and '' != interactionTime ">
                interaction_time,
            </if>
            <if test="null != organizationId ">
                organization_id
            </if>
        </trim>
        <trim prefix="values (" suffix=")" suffixOverrides=",">
            <if test="null != type ">
                #{type,typeHandler=com.chinaunicom.iotdb.handler.JsonIntegerTypeHandler },
            </if>
            <if test="null != traceId and '' != traceId">
                #{traceId,typeHandler=com.chinaunicom.iotdb.handler.JsonIntegerTypeHandler },
            </if>
            <if test="null != imei and '' != imei">
                #{imei,typeHandler=com.chinaunicom.iotdb.handler.JsonIntegerTypeHandler },
            </if>
            <if test="null != topic and '' != topic">
                #{topic,typeHandler=com.chinaunicom.iotdb.handler.JsonIntegerTypeHandler },
            </if>
            <if test="null != information and '' != information">
                #{information,typeHandler=com.chinaunicom.iotdb.handler.JsonIntegerTypeHandler },
            </if>
            <if test="null != interactionTime and '' != interactionTime ">
                #{interactionTime,typeHandler=com.chinaunicom.iotdb.handler.JsonIntegerTypeHandler },
            </if>
            <if test="null != organizationId ">
                #{organizationId,typeHandler=com.chinaunicom.iotdb.handler.JsonIntegerTypeHandler },
            </if>
        </trim>
    </insert>

@Data
@TableName(autoResultMap = true)
public class DmpDeviceReportInformation implements Serializable
{
    private static final long serialVersionUID = 1L;

    private Long id;

    /**
     * 消息类型1:消息上报 2:消息下发
     */
 @TableField(typeHandler = JsonIntegerTypeHandler.class)
    private Integer type;
    }

mybatis-plus:
   type-handlers-package: com.chinaunicom.iotdb.handler