java - hibernate 多对多加入条件

Question

+-------+    +--------------|     +-------+
| BOY   |    | BOY_GIRL     |     | GIRL  | 
+-------+    +--------------|     +-------+
| id    |    | id           |     | id    |
| name  |    | boy_id       |     | name  |
| birth |    | girl_id      |     | birth |
+-------+    | start_dating |     +-------+
             +--------------|

START_DATING 是 TIMESTAMP 或 DATE 的类型>

我有两个具有多对多关系的 bean Boy 和 Girl

@ManyToMany(fetch = FetchType.LAZY)
@JoinTable(name = "BOY_GIRL", joinColumns = {@JoinColumn(name = "BOY_ID")}, inverseJoinColumns = {@JoinColumn(name = "GIRL_ID")})
public Set<Girl> getGirls() {
    return girls;
}

现在，如果我想获得符合以下条件的女孩列表，我该如何使用 HQL 进行选择查询:

where boy_id = (some_boy_id) and START_DATING > (some_timestamp)

Answer 1

我认为你必须创建一个 BoyGirl 类，因为表 BOY_GIRL 不是一个简单的多对多表(如果是，那么列必须仅为 boy_id 和 girl_id)。所以你应该做的是创建 BoyGirl 类，然后将 BOY 一对多映射到 BOY_GIRL 并映射 GIRL 到 BOY_GIRL 一对多

表关系

+-------+               +--------------+               +-------+
| BOY   |               | BOY_GIRL     |               | GIRL  | 
+-------+               +--------------|               +-------+
| id    | 0..* --- 1..1 | id           | 1..1 --- 0..* | id    |
| name  |               | boy_id       |               | name  |
| birth |               | girl_id      |               | birth |
+-------+               | start_dating |               +-------+
                        +--------------+

Java 类

public class BoyGirl {
  private long id;
  private Boy boy;
  private Girl girl;
  private Date startDating;
}

public class Boy {
  //other attributes omitted
  private Set<BoyGirl> boyGirls;
}

public class Girl {
  //other attributes omitted
  private Set<BoyGirl> boyGirls;
}

您需要的选择查询

// I'm using criteria here, but it will have the same result as your HQL

public List getGirls(Boy boy, Date startDating) {
  Criteria c = sessionFactory.getCurrentSession().createCriteria(BoyGirl.class);
  c.add(Restrictions.eq("boy.id", boy.getId());
  c.add(Restrictions.lt("startDating", startDating);

  List<BoyGirl> boyGirls = (List<BoyGirl>) c.list();
  // at this point you have lazily fetch girl attributes
  // if you need the girl  attributes to be initialized uncomment line below
  // for (BoyGirl boyGirl : boyGirls) Hibernate.initialize(boyGirl.getGirl());

  return boyGirls;
}