Play Framework 1.x中的模型ID的8位随机值

Question

I would like to use random 8 digit number id for model in play! 1.2.5 play! 1.2.5 instead of auto_increment value and also without creating a random value , assigning it to id by myself. I do not know it is possible or not. I really googled about it but I could not find anything.

for the answer below. Here is what i need in my project. Suppose that i have a user object which has 2 attr. name and surname. With the defult creation of this object, JPA assing a auto_inc value for the id of this object.

@Entity
public class User extends Model{
    public String name;
    public String surname;
}

And here i have createUser method in my controller.

public static void createUser(String name, String surname){
     User user = new User();
     user.name = name;
     user.surname = surname;
     /* it seems to me that the answer below can be a solution for what i want like that
      * user.id = javaGenereted8digitNumId();
      * But I dont want this. I want it is handled in model class
      * and I guess it can be with JPA GenericModel. am I right?
      */

     user.save();

}

Answer 1

use:

int ID = (int) (Math.Random()*(99999999-a)+a); //a being the smallest value for the ID

and if you want to include the 0's on the left, use:

import java.text.DecimalFormat;

and in your code:

DecimalFormat fmt = new DecimalFormat("00000000");
int ID = Integer.parseInt(fmt.format((int) (Math.Random()*(99999999-a)+a)));

EDIT: This is an update to your update of the question.

If you want the model class of User to create its own unique 8digit ID everytime, i suggest you make a static variable that saves the last currently used ID for all User objects created. This way on creation of a new user, it will simply create a new user with the next available ID, this will of course be limited to 99999999 ID's. If you want to go further then this, you will need to create a very large static String containing all the used ID's seperated by spaces, and everytime you want to add a user, it will check for the ID availability by using .contains("ID") method

Here's an example of what your User class should look like i believe:

public class User extends Model
{
    public String name, surname;
    public int ID;
    public static int lastID;
    public static String usedIDs;

    public User(String name, String surname) //regular User objects
    {
        this.name = name;
        this.surname = surname;
        ID = ++lastID;
        usedID's += ID + " ";
    }

    public User(String name, String surname, int n) //first User object created
    {
        this.name = name;
        this.surname = surname;
        ID = 1;
        lastID = 1;
        usedID's = ID + " ";
    }

//rest of your methods