Project, project_id

@OneToMany(mappedBy = "project")

    private Set<Ap> apSet =new HashSet<Ap>();

Ap, ap_id

@ManyToOne(fetch = FetchType.EAGER)

    @JoinColumn( name = "project_id",nullable = false)

    private Project project;

注意不要有cascade之类的，会冲突

ManyToOne里的name要跟OneToMany的对象的id对应

OneToMany里的mappedBy要跟ManyToOne的变量对应