java – play framework Exception – field .. No default value

Running my play framework applet, I get the following exception:

Error play spit out in browser

I have 2 physical mail and users

1)Mail. java

@Entity
public class Mail extends Model {


   public String title;

   public Date sentAt;
   @OneToMany
   public List<User> sentTO;
   @OneToMany
   public List<User> sentBCC;


    public String content;

    @ManyToOne
    public User author;

//more code ...
}

2)User. java

@Entity
public class User extends Model {

    public String email;
    public String password;
    public String fullname;
    public boolean isAdmin;

    @OneToMany(mappedBy="author",cascade= CascadeType.ALL)
    public List<Mail> mails ;

    public User(String email,String password,String fullname) {
        this.email = email;
        this.password = password;
        this.fullname = fullname;
    }

}

Full stack

I have been groping for this mistake for some time, but I can't solve it Can someone help me understand why I received this error?

Solution

First, SendTo and sendbcc should be mapped to @ manytomany

Secondly, by default, join tables are used to implement non directed @ onetomany mappings and all @ manytomany mappings, and the default generation policy of join table names does not allow you to have multiple such relationships between the same classes

You need to specify the connection table name explicitly:

@ManyToMany
@JoinTable(name = "User_Mail_To")
public List<User> sentTO;

@ManyToMany
@JoinTable(name = "User_Mail_Bcc")
public List<User> sentBCC;