Spring 引导 JPA OneToMany 和 ManyToOne 为我带来 JoinTable 中的所有寄存器

Question

Hi im using JPA and i need to use OneToMany and ManyToOne, it works well with one register but when i insert more than one register the result contains all data registered in jointable.

Example:

I have the following tables, User and Company , and Join table USER_COMPANY_REL

Table User

USER_ID
NAME
ADDRESS
...

Table Company

COMPANY_ID
NAME
WEB_SITE
...

USER_COMPANY_REL

REL_ID
USER_ID
COMPANY_ID

I have Data of 3 Users and 2 Companies, if i have in my USER_COMPANY_REL table one user with one company, it works, if i put the same user with another comany it works, but when i put another user with another company, when i get Data from some user (with one or more companies registered) the result is: User info plus as many companies as are registered in Join table.

I have this in my Spring Boot code

Class COMPANY

...
 @ManyToOne
      @JoinTable(name = "USER_COMPANY_REL",
              joinColumns = {@JoinColumn(name = "COMPANY_ID", insertable = false,
                      updatable = false, referencedColumnName = "COMPANY_ID")},
              inverseJoinColumns = {@JoinColumn(name = "USER_ID", insertable = false,
                      updatable = false, referencedColumnName = "USER_ID")}
      )
    private User user;
...

Class USER

...
@OneToMany
      @JoinTable(name = "USER_COMPANY_REL",
              joinColumns = {@JoinColumn(name = "USER_ID", referencedColumnName = "USER_ID")},
              inverseJoinColumns = {@JoinColumn(name = "COMPANY_ID", referencedColumnName = "COMPANY_ID")}
      )
...

And this is postman result

Why is this happening? can you help me?

Regards

Answer 1

First of all use auto increment column (ID for example, or use any other auto generated id strategy) in both tables and column COMPANY_ID and USER_ID put as unique columns to avoid duplicates. You should use only @JoinColumns in Company class. Here is an example:

@ManyToOne
@JoinColumns(@JoinColumn(name = "COMPANY_ID", insertable = false,
                  updatable = false, referencedColumnName = "COMPANY_ID"),
             @JoinColumn(name = "USER_ID", insertable = false,
                  updatable = false, referencedColumnName = "USER_ID"))
private User user;

On the other side (in User class) you should have only this:

@OneToMany(fetch = FetchType.LAZY, mappedBy = "user")
List<Company> companies=new LinkedList<Company>();

It can be List or Set of companies.