JPA多对多关系创建两个联接表
我正在尝试在User
和FileObject
类之间创建多对多关系,并假设用户可以访问许多文件对象,并且文件对象可以被许多用户访问,并且一对多关系如下一个用户可以拥有多个文件,但一个文件只能由一个用户拥有.这是我的代码:
I am trying to create a many-to-many relationship between User
and FileObject
classes with the assumption user can access many file objects and file object can be accessed by many user and one-to-many relationship as one user can own many files but one file can only be owned by one user. Here is my code:
@Entity
public class User {
@Id
@GeneratedValue(strategy = GenerationType.TABLE)
public int id;
public String firstname;
public String lastname;
public String publicAttributes;
public String privateAttributes;
@ManyToOne
private Department department;
@OneToMany(mappedBy = "user")
public List<Device> devices = new ArrayList<Device>();
@OneToMany(mappedBy = "userCreator")
public List <FileObject> fileOwned = new ArrayList <FileObject>();
@ManyToMany
@JoinTable(name="USER_FILE_ACCESS")
public List<FileObject> fileHasAccess = new ArrayList<FileObject>();
}
@Entity
public class FileObject {
@Id
@GeneratedValue(strategy = GenerationType.TABLE)
public int id;
String checksum;
@OneToMany(mappedBy = "fileObject")
public List<Policy> policies = new ArrayList<Policy>();
byte[] encryptedFileKey;
byte[] iv;
@ManyToOne
public User userCreator;
@ManyToMany
public List<User> listUserAccessor = new ArrayList<User>();
}
从理论上讲,它应该只创建一个联接表,即USER_FILE_ACCESS,但是当我运行脚本时,它将创建两个联接表,我不确定为什么.
In theory it should only create one join table namely USER_FILE_ACCESS but when I ran the script then it creates two join tables and I am not sure why.
以下是SQL命令的摘录:
Here are the excerpt of the SQL commands:
show tables;
+------------------+
| Tables_in_cpabe |
+------------------+
| DEPARTMENT |
| DEVICE |
| FILEOBJECT |
| FILEOBJECT_USER |
| POLICY |
| SEQUENCE |
| USER |
| USER_FILE_ACCESS |
+------------------+
show columns from FILEOBJECT_USER;
+---------------------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------------------+---------+------+-----+---------+-------+
| FileObject_ID | int(11) | NO | PRI | NULL | |
| listUserAccessor_ID | int(11) | NO | PRI | NULL | |
+---------------------+---------+------+-----+---------+-------+
show columns from USER_FILE_ACCESS;
+------------------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------------+---------+------+-----+---------+-------+
| User_ID | int(11) | NO | PRI | NULL | |
| fileHasAccess_ID | int(11) | NO | PRI | NULL | |
+------------------+---------+------+-----+---------+-------+
如何使联接表成为一个表?
How do I make join table to be only one table?
如果您想建立双向关系,则:
If you want to have a bi-directional relationship then:
@Entity
public class User {
@ManyToMany
@JoinTable(name="USER_FILE_ACCESS"
joinColumns=@JoinColumn(name="user_id"),
inverseJoinColumns=@JoinColumn(name="fileHasAccess_ID "))
public Set<FileObject> fileHasAccess;
@Entity
public class FileObject {
@ManyToMany
@JoinTable(name="USER_FILE_ACCESS"
joinColumns=@JoinColumn(name="fileHasAccess_ID"),
inverseJoinColumns=@JoinColumn(name="user_id"))
public Set<User> listUserAccessor;
更新
尝试使用SEt而不是列表.
Try to use SEt instead of a List.
您还可以尝试另一个双向选项.因此,在非所有权方面,您应按以下方式进行映射:
And you can also try another bi-directional option. So on the non-owning side, you would map as follows:
@ManyToMany(mappedBy = "fileHasAccess")
public Set<User> listUserAccessor;
还要仔细检查列名..我可能输入的内容与您在数据库中实际输入的内容不同.
Also, double-check the column names .. I may have put something different then what you actually have in the DB.