Question

我需要将2个表连接到一个具有某些条件的对象中。我有以下内容：

@Entity
@Table(name = "polling")
public class Polling extends DomainIdObject {

    @ManyToOne
    @JoinColumn(name = "owner_id")
    private Person owner;

    @Column(name = "poll_name")
    private String name;

    @Column(name = "description")
    private String description;

    @ManyToMany(targetEntity = PollingSchedule.class, mappedBy = "polling", fetch = FetchType.EAGER)
    private List<PollingSchedule> variants;

    @Column(name = "start_time")
    private LocalDateTime startTime;

    @Column(name = "end_time")
    private LocalDateTime endTime;

    //getters and setters

@Entity
@Table(name = "polling_schedule")
public class PollingSchedule extends DomainIdObject {

    @JoinColumn(name = "polling_id")
    private Polling polling;

    @Column(name = "poll_var")
    private String pollingVariant;

    //gettters and setters

但是当我执行以下代码时：

Query query = getEntityManager().createNativeQuery("SELECT * FROM polling p WHERE p.id=1", Polling.class);
List list = query.getResultList();
List<PollingSchedule> variants = ((Polling) list.get(0)).getVariants();

变种列表为空。 DB中的表格如下：

polling
|id|owner_id|poll_name|description|start_time|end_time|

polling_schedule
|id|polling_id|poll_var|

因此，在结果中我希望Polling对象只包含那些PollingVariants，它们在polling_schedule表中有相应的polling_id。

我尝试使用Filter，SecondaryTable注释，但它对我不起作用（或者我使用它不正确）。

我使用hibernate4和spring boot 1.5.1

有人可以帮助我吗？

Answer 1

我认为Polling和PollingSchedule之间的关系是一对多（不是多对多）。由于您需要在这些对象之间建立双向关系，因此您应该像这样更改它们：

Pooling.java

@Entity
@Table(name = "polling")
public class Polling extends DomainIdObject {
    ...
    @OneToMany(mappedBy="polling")
    private List<PollingSchedule> variants;
    ...
}

PoolingSchedule.java

@Entity
@Table(name = "polling_schedule")
public class PollingSchedule extends DomainIdObject {

    @ManyToOne
    @JoinColumn(name = "polling_id")
    private Polling polling;
    ...
}

通过jpa在一个java对象中连接两个表

1 个答案: