org.springframework.jdbc.IncorrectResultSetColumnCountException:列数不正确:预期1,实际38

Question

我正在使用JdbcTemplate从数据库中检索Bean.这是我的方法:

public List<trackerv3Livedata>  getTrackerData() {
    return List<trackerv3Livedata> live = (List<trackerv3Livedata>) jdbcTemplate.queryForList("select * from mmitrackerv3_livedata where accountid =?",new Object[]{aid}, trackerv3Livedata.class);
}

和trackerv3Livedata bean结构如下:

public class trackerv3Livedata implements Serializable {

    private static final long serialVersionUID = 2409168269491619888L;

    private int deviceid;
    private Long timestamp;
    private Mmitrackerv3Device mmitrackerv3Device;
    private Mmitrackerv3Account mmitrackerv3Account;
    private double latitude;
    private double longitude;
    private Double altitude;
    private Double speedkph;
    private Double heading;
    private Double gpssignal;
    private Integer geozoneid;
    private Double distancekm;
    private Double gsmsignal;
    private Double mainpower;
    private Integer laststatustime;
    private Double internalbattry;
    private Double temperature;
    private Short dinput1;
    private Short dinput2;
    private Short dinput3;
    private Short dinput4;
    private Short dinput5;
    private Short dinput6;
    private Short dinput7;
    private Short dinput8;
    private Short ainput1;
    private Short ainput2;
    private Short ainput3;
    private Short ainput4;
    private Short doutput1;
    private Short doutput2;
    private Short doutput3;
    private Short doutput4;

    /* There are Some Getter And Setter Method With Constructor */
}

在我的方案中,完全可能不会得到我的查询,所以我的问题是如何解决以下错误消息.

org.springframework.jdbc.IncorrectResultSetColumnCountException: Incorrect column count: expected 1, actual 38

在我看来,我应该回到null而不是抛出异常.我怎样才能解决这个问题？提前致谢.

Answer 1

发生这种情况是因为您使用的queryForList方法不支持多列.从JdbcTemplate查看queryForList的实现

public <T> List<T> More ...queryForList(String sql, Object[] args, Class<T> elementType) throws DataAccessException 
{
    return query(sql, args, getSingleColumnRowMapper(elementType));
}

getsingleColumnRowMapper()方法创建一个新的RowMapper,用于从单个列读取结果对象.您可以使用下面给出的方法.

public <T> List<T> query(String sql, Object[] args, RowMapper<T> rowMapper) throws DataAccessException        
 {
    return query(sql, args, new RowMapperResultSetExtractor<T>(rowMapper));
}

Answer 2

JdbcTemplate方法

queryForList(String sql, Class<T> elementType)

对于单列查询很有用，您只能指定列类型。如果您在ResultSet中需要多个列，则使用起来更准确

query(String sql, RowMapper<T> rowMapper)

作为RowMapper的实现，您可以使用自己的实现，或

jdbcTemplate.query(sql, new BeanPropertyRowMapper<T>(clazz));

因此，在您的情况下，可能是：

public List<Trackerv3Livedata> getTrackerData() {
    String sql = "SELECT * FROM mmitrackerv3_livedata mlive " +
                 "JOIN mmitrackerv3_device mdevice ON mlive.accountid = " +
                 "mdevice.accountid WHERE mlive.accountid = " + aid;

    return jdbcTemplate.query(sql,
            new BeanPropertyRowMapper<Trackerv3Livedata>(Trackerv3Livedata.class));
}

Answer 3

应该尝试使用Rowmapper，就像在查询API 时使用它一样。

希望能解决您的问题。