Question

我有三张桌子一个是busStation 另一个是busLine busLine包含许多破坏，我想用hibernate来映射连接，但我的老板让我使用 busStation_to_busLine表与两个表关联。他说这种方式很方便转换为hbase（目前我们使用的是mysql）。所以我必须选择busStation，然后选择busStation_to_busLine，并选择busLine，以获得我想要的东西。怎么可以让我的代码更简单，不选择三个表，而不是受到hibernate连接问题的困扰。那么我应该使用什么dao框架，或者如何让我的代码更容易编写？或者设计更好的表结构？

更新它报告例外

引起：org.hibernate.MappingException：无法确定类型 for：java.util.List，at table：bus_station，for columns： [org.hibernate.mapping.Column（巴士线路）]

我的实体和表格是

@Entity
@Table(name="bus_line")
@NamedQuery(name="BusLine.findAll", query="SELECT b FROM BusLine b")
public class BusLine implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    @Column(unique=true, nullable=false)
    private Long id;

    @Column(nullable=false)
    private Long firstExpressTime;

    @Column(nullable=false)
    private Long lastExpressTime;

    private Integer lineDirection;

    @Column(nullable=false, length=10)
    private String lineName;

    @Column(nullable=false)
    private Long originatingStationID;

    @Column(nullable=false, length=10)
    private String originatingStationName;

    @Column(nullable=false)
    private Long terminusID;

    @Column(nullable=false, length=10)
    private String terminusName;

    @ManyToMany(mappedBy="busLines")
    private List<BusStation> busStations = new ArrayList<BusStation>();
    omit getter and setter method
}

@Entity
@Table(name="bus_station")
@NamedQuery(name="BusStation.findAll", query="SELECT b FROM BusStation b")
public class BusStation implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    @Column(unique=true, nullable=false)
    private Long id;

    @Column(nullable=false)
    private Double stationLat;

    @Column(nullable=false)
    private Double stationLng;

    @Column(nullable=false, length=20)
    private String stationName;

    @JoinTable(name="bus_line_to_station",joinColumns = @JoinColumn(name="stationID"),
            inverseJoinColumns=@JoinColumn(name="lineID"))
    private List<BusLine> busLines = new ArrayList<BusLine>();

    omit setter and getter method
}

   CREATE TABLE `bus_line` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT ,
  `lineName` varchar(10) NOT NULL ,
  `originatingStationName` varchar(10) NOT NULL ,
  `originatingStationID` bigint(20) NOT NULL ,
  `terminusID` bigint(20) NOT NULL ,
  `terminusName` varchar(10) NOT NULL ,
  `firstExpressTime` datetime NOT NULL ,
  `lastExpressTime` datetime NOT NULL ,
  `lineDirection` int(3) DEFAULT '1' ,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `bus_line_to_station` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT ,
  `lineID` bigint(20) NOT NULL ,
  `stationID` bigint(20) NOT NULL ,
  `stationOrder` int(3) NOT NULL ,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `bus_station` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT ,
  `stationName` varchar(20) NOT NULL ,
  `stationLng` double NOT NULL ,
  `stationLat` double NOT NULL ,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Answer 1

您可以使用@ManyToMany来映射BusStation和BusLine之间的关系

@Entity
public class BusStation {
    ...
    @ManyToMany
    @JoinTable(name = "busStation_to_busLine", joinColumns = @JoinColumn(name = "busStation_id"),
      inverseJoinColumns = @JoinColumn(name = "busLine_id")
    private List<BusLine> busLines = new ArrayList<BusLine>();
    ...
}

@Entity
public class BusLine {
    ...
    @ManyToMany(mappedBy = "busLines")
    private List<BusStation> busStations = new ArrayList<BusStation>();
    ...
}

如何避免加入和方便扩展

1 个答案: