Question

用户有以下内容：

@ManyToMany(mappedBy = "votedDownBy")
private Set<Foo> votedDown =new HashSet<Foo>();

@ManyToMany(mappedBy = "favouritedBy")
private Set<Foo> favourites = new HashSet<Foo>();

相应的Foo有这些：

@ManyToMany
private Set<User> votedDownBy = new HashSet<User>();

@ManyToMany
private Set<User> favouritedBy = new HashSet<User>();

部署时我没有为votedDownBy_id提供默认值...而且我不知道为什么？

Answer 1

@ManyToMany映射使用连接表完成。在您的情况下，必须有一个Foo_User表具有这些映射。即Foo_id和User_id列。（将Foo_id和User_id替换为相应的主键。同时将Foo_User替换为Table1_Table2，其中Table1是Foo和{{ 1}} Table2）

您可以使用User注释覆盖这些默认值：

@JoinTable

和

@ManyToMany(mappedBy = "votedDownBy")
@JoinTable(name="User_Foo_Votedown", 
            joinColumns={@JoinColumn(name="User_ID")}, 
            inverseJoinColumns={@JoinColumn(name="Foo_id")})
private Set<Foo> votedDown =new HashSet<Foo>();

@ManyToMany(mappedBy = "favouritedBy")
@JoinTable(name="User_Foo_Fav", 
            joinColumns={@JoinColumn(name="User_ID")}, 
            inverseJoinColumns={@JoinColumn(name="Foo_id")})
private Set<Foo> favourites = new HashSet<Foo>();

您还可以将@ManyToMany(mappedBy = "votedDown") private Set<User> votedDownBy = new HashSet<User>(); @ManyToMany(mappedBy = "favorites") private Set<User> favouritedBy = new HashSet<User>();注释放在mappedBy中，将User放在JoinTable中，因为这是一种对称的双向关系。

Answer 2

只需将连接表添加到每个映射修复它，foo类现在看起来像这样：

@ManyToMany
@JoinTable(name="user_foo_vote_down")
private Set<User> votedDownBy = new HashSet<User>();

@ManyToMany
@JoinTable(name="user_foo_favourite")
private Set<User> favouritedBy = new HashSet<User>();

Hibernate没有发现默认值具有多个到同一实体的多个映射

2 个答案: