使用JoinTable

Question

我試圖做使用Java2EE類似Twitter的項目，這裏的數據庫的簡單示意圖。
提及，追隨者和以下是三個JoinTable。 （需要注意的是提到，跟隨，跟隨一位用戶領域有User.username爲外鍵。） 我有與第一個問題，導致我的部署失敗與此異常：

異常說明：映射在元素[字段提及]上的引用列名稱[用戶名]不對應映射引用上的有效字段。

下面是兩個實體的映射。

鳴叫：

public class Tweet implements Serializable { 
    private static final long serialVersionUID = 1L; 
    @Id 
    @GeneratedValue(strategy = GenerationType.IDENTITY) 
    @Basic(optional = false) 
    @NotNull 
    @Column(name = "id", nullable = false) 
    private Integer id; 

    ... 

    @JoinColumn(name = "user", referencedColumnName = "username") 
    @ManyToOne 
    User user; 
    @JoinTable(name = "Mention", joinColumns = { 
     @JoinColumn(name = "tweet", referencedColumnName = "id")}, inverseJoinColumns = { 
     @JoinColumn(name = "mentioned", referencedColumnName = "username")}) 
    @OneToMany 
    private Collection<Tweet> mentions; 

用戶：

public class User implements Serializable { 

    private static final long serialVersionUID = 1L; 
    @Id 
    @Basic(optional = false) 
    @NotNull 
    @Size(min = 1, max = 50) 
    @Column(name = "username", nullable = false, length = 50) 

    ... 

    @OneToMany(mappedBy = "user") 
    Collection<Tweet> tweets; 
    @JoinTable(name = "Following", joinColumns = { 
     @JoinColumn(name = "user", referencedColumnName = "username")}, inverseJoinColumns = { 
     @JoinColumn(name = "following", referencedColumnName = "username")}) 
    @OneToMany 
    Collection<User> following; 
    @JoinTable(name = "Followers", joinColumns = { 
     @JoinColumn(name = "user", referencedColumnName = "username")}, inverseJoinColumns = { 
     @JoinColumn(name = "follower", referencedColumnName = "username")}) 
    @OneToMany 
    Collection<User> followers; 
    @OneToMany(mappedBy = "mentions") 
    Collection<Tweet> mentioning; 

這有什麼錯我的映射？ 有人可以指點我的解決方案嗎？

Answer 1

我認爲你必須改變

@JoinColumn(name = "mentioned", referencedColumnName = "username") 

指定用戶表

@JoinColumn(name = "mentioned", referencedColumnName = "user") 

由於基本消息說你tweet表沒有一個外鍵字段username它不像你所說的那樣user

這個 - >private Collection<Tweet> mentions;也應該是一對多的col用戶的經文讓你有

@OneToMany 
@JoinTable(
    name = "Mention", 
    joinColumns = { 
     @JoinColumn(name = "tweet", referencedColumnName = "id") 
    }, 
    inverseJoinColumns = { 
     @JoinColumn(name = "mentioned", referencedColumnName = "user") 
    } 
)  
private Collection<User> mentions;