Java 正在加载惰性子集合

我有类似的数据模型

class Office
{
   @ManyToOne
   @JoinColumn(name = "cafeteria_id")
   Cafeteria cafeteria;
}

class Cafeteria
{
   @OneToMany(mappedBy="cafeteria")
   @LazyCollection(value=LazyCollectionOption.EXTRA)
   List<Chair> chairs;
}

class Chair
{
    @ManyToOne
    @JoinColumn(name = "cafeteria_id")
    Cafeteria cafeteria;
}

---

上面的查询很好，但有一个例子，我想要一个能够急切地加载所有椅子（o.caffeeta.chairs）的查询。我应该如何修改查询以急切地获取所有椅子？

在

OneToMany

注释中使用

fetch

属性。可以根据需要多次映射同一关系：

class Cafeteria {
   @OneToMany(mappedBy="cafeteria")
   @LazyCollection(value=LazyCollectionOption.EXTRA)
   List<Chair> chairs;

   @OneToMany(fetch = FetchType.EAGER, mappedBy="cafeteria")
   List<Chair> eagerlyLoadedChairs;
}

---

您有两个选项，可以将提取类型从

惰性

更改为

急切

，但每次从自助餐厅加载对象时，这将始终加载您的

椅子列表

像这样：

@OneToMany(mappedBy="cafeteria", fetch=FetchType.EAGER)
@LazyCollection(value=LazyCollectionOption.FALSE)
List<Chair> chairs;

// Lazy loading
select o from Office o inner join o.cafeteria c inner join c.chairs ch where c.someThing = ?

// Eager loading
select o from Office o inner join o.cafeteria c inner join c.eagerlyLoadedChairsch where c.someThing = ?

@OneToMany(mappedBy="cafeteria", fetch=FetchType.EAGER)
@LazyCollection(value=LazyCollectionOption.FALSE)
List<Chair> chairs;

Hibernate.initialize(cafeteria.getChairs());