Question

我有两个类，它们之间有两个关系。

用户类：

@Entity
@Table(name="User")
public class User implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name="Id")
    private long id;

    @OneToMany(cascade = CascadeType.ALL, fetch=FetchType.EAGER, mappedBy="admin")
    private Set<Group> ownedGroup;

    @ManyToMany(cascade = CascadeType.ALL, fetch=FetchType.EAGER, mappedBy="members")
    private Set<Group> memberGroups;

    //.......
}

群组类：

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

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name="Id")
    private long id;

    @NotNull
    @ManyToOne(cascade=CascadeType.ALL, fetch=FetchType.EAGER)
    @JoinColumn(name="Admin", referencedColumnName="Id")
    private User admin;

    @ManyToMany(cascade=CascadeType.ALL, fetch=FetchType.EAGER)
    @JoinTable(name = "Group_User", 
        joinColumns = @JoinColumn(name = "Group"), 
        inverseJoinColumns = @JoinColumn(name = "User"))
    private Set<User> members;
    //....
}

当我想启动应用程序时，我遇到了这个例外：

org.hibernate.AnnotationException: Use of @OneToMany or @ManyToMany targeting an unmapped class: com.myproject.model.User.memberGroups[com.querydsl.core.group.Group]

我看到了其他类似的帖子，但显然他们没有使用javax.persistence.Entity，这是导致此错误的根本原因。知道如何解决这个问题吗？

Answer 1

群组是保留关键字。使用反引号来转义保留的关键字。查看this回答。

@Table(name = "`Group`")

不幸的是，您的@ManyToMany映射不正确。像这样更新您的Group实体：

@Entity
@Table(name="`Group`") // Change your table name
public class Group implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name="Id")
    private long id;

    @NotNull
    @ManyToOne(cascade=CascadeType.ALL, fetch=FetchType.EAGER)
    @JoinColumn(name="Admin", referencedColumnName="Id")
    private User admin;

    @ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    @JoinTable(
        name = "Group_User", 
        joinColumns = @JoinColumn(name = "group_id", referencedColumnName = "id"), //Give a column name 'group_id' and map it to Group primary key id
        inverseJoinColumns = @JoinColumn(name = "user_id", referencedColumnName = "id") //Give a column name 'user_id' and map it to User primary key id.
    )
    private Set<User> members;

    ...

}

在两个实体之间存在多个关系时抛出异常

1 个答案: