hibernate - 你如何检索嵌套的集合？

Question

是否有我遗漏的注释或者这是对 hibernate 检索的限制？

实体:

class A {
   Long id;
   Set<B> b;

   @ManyToMany(fetch = FetchType.EAGER)
   @JoinTable(name = "A_B", joinColumns = @JoinColumn(name = "A_ID"), inverseJoinColumns = @JoinColumn(name = "B_ID")
   public Set<B> getBs() {
      return b;
   }

}

class B {
   Long id;
   Set<C> c;

   @ManyToMany(fetch = FetchType.EAGER)
   @JoinTable(name = "B_C", joinColumns = @JoinColumn(name = "B_ID"), inverseJoinColumns = @JoinColumn(name = "C_ID")
   public Set<C> getCs() {
      return C;
   }

}

DAO:

class ADaoImpl {    
   public A load(Long id) {
      return new A((A) session.load(A.class, id);
   }
}

当我尝试加载 A 时，我得到一个

Caused by: java.lang.NullPointerException
at org.hibernate.engine.internal.StatefulPersistenceContext.getLoadedCollectionOwnerOrNull(StatefulPersistenceContext.java:853)

Answer 1

我有一个与此非常相似的问题是我有嵌套集，并且每个的 hashCode 方法都显示在堆栈跟踪中。在hashCode方法中，它们相互引用，所以我在hashcode方法中删除了对每个对象的引用，我不再得到这个异常