“非法尝试将非集合映射为@ OneToMany，@ ManyToMany或@CollectionOfElements” [英] “Illegal attempt to map a non collection as a @OneToMany, @ManyToMany or @CollectionOfElements”

问题描述

早上好Stackoverflow，

Good morning Stackoverflow,

我遇到的问题是它给了我错误：

I have the problem that it gives me the error:

无法创建sessionFactory
object.org.hibernate.AnnotationException：非法尝试将非
集合映射为@ OneToMany，@ ManyToMany或@CollectionOfElements：
nl.scalda .pasimo.model.employeemanagement.EducationTeam.coachGroups

Failed to create sessionFactory object.org.hibernate.AnnotationException: Illegal attempt to map a non collection as a @OneToMany, @ManyToMany or @CollectionOfElements: nl.scalda.pasimo.model.employeemanagement.EducationTeam.coachGroups

您知道为什么吗？

@OneToMany(cascade=CascadeType.ALL, targetEntity=CoachGroup.class)
@JoinColumn(name="id")
private TreeSet<CoachGroup> coachGroups = new TreeSet<>();
private SessionFactory factory;

private void initialiseFactory() {
    try {
        factory = new Configuration().configure().buildSessionFactory();
    } catch (Throwable ex) {
        System.err.println("Failed to create sessionFactory object." + ex);
        throw new ExceptionInInitializerError(ex);
    }
}

推荐答案

异常很简单，它说：试图将非集合映射为@ OneToMany，@ ManyToMany或@CollectionOfElements ，因此原因很明显，如果我们看一下 Hibernate 集合映射文档明确指出：

The Exception is straightforward and says : Illegal attempt to map a non collection as a @OneToMany, @ManyToMany or @CollectionOfElements, so the cause is obvious here and if we take a look at the Hibernate Collection mapping documentation it clearly states that:

根据要求，必须将持久性集合值字段声明为接口类型（请参见示例7.2， 使用@OneToMany和@JoinColumn进行集合映射）。实际的接口可能是 java.util.Set ， java.util.Collection ， java .util.List ， java.util.Map ， java.util.SortedSet ， java.util.SortedMap ...

As a requirement persistent collection-valued fields must be declared as an interface type (see Example 7.2, "Collection mapping using @OneToMany and @JoinColumn"). The actual interface might be java.util.Set, java.util.Collection, java.util.List, java.util.Map, java.util.SortedSet, java.util.SortedMap...

您使用了 TreeSet 这是一个实现 Set< E> 和 SortedSet< E> 接口的 class 。因此，您的实际映射不适用于 TreeSet ，您应该使用 Set< CoachGroup> 而不是 TreeSet< CoachGroup> ：

And you used TreeSet which is an implementation class for both Set<E> and SortedSet<E> interfaces. So your actual mapping won't work with TreeSet, you should use a Set<CoachGroup> instead of a TreeSet<CoachGroup>:

private Set<CoachGroup> coachGroups = new HashSet<CoachGroup>();

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