java – 带有集合的JPA实体对分离成员上的contains方法返回false

Group.java：

@Entity
@Table(name = "groups")
public class Group {

    @Id
    @GeneratedValue
    private int id;


    @ManyToMany
    @JoinTable(name = "groups_members",joinColumns = {
            @JoinColumn(name = "group_id",referencedColumnName = "id")
    },inverseJoinColumns = {
            @JoinColumn(name = "user_id",referencedColumnName = "id")
    })
    private Collection<User> members;


    //getters/setters here

}

User.java：

@Entity
@Table(name = "users")
public class User {

    private int id;
    private String email;

    private Collection<Group> groups;

    public User() {}

    @Id
    @GeneratedValue
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    @Column(name = "email",unique = true,nullable = false)
    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    @ManyToMany(fetch = FetchType.LAZY)
    @JoinTable(name = "groups_members",joinColumns = {
            @JoinColumn(name = "user_id")
    },inverseJoinColumns = {@JoinColumn(name = "group_id")})
    public Collection<Group> getGroups() {
        return groups;
    }

    public void setGroups(Collection<Group> groups) {
        this.groups = groups;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (!(o instanceof User)) return false;

        User user = (User) o;

        if (id != user.id) return false;
        return email.equals(user.email);
    }

    @Override
    public int hashCode() {
        int result = id;
        result = 31 * result + email.hashCode();
        return result;
    }
}

我尝试为具有一个成员的组运行以下代码段,其中group是刚从JpaRepository检索的实体,user是该组和分离实体的成员.

Collection<User> members = group.getMembers();
            System.out.println(members.contains(user)); //false
            User user1 = members.iterator().next();
            System.out.println(user1.equals(user)); //true

经过一些调试后,我发现在.contains()调用期间调用了User.equals(),但是Hibernate集合中的用户有空字段,因此.equals()被评估为false.

那么为什么它如此奇怪以及在这里调用.contains()的正确方法是什么？