This document defines the schema for three database tables - T_Users to store user accounts, T_Roles to define roles, and T_Users_Roles_Associations to establish a many-to-many relationship between users and roles. It also defines Java entity classes for User and Role with fields and annotations to map to the database tables and manage the many-to-many relationship.

1. CREATE TABLE T_Users (
idUser int PRIMARY KEY AUTO_INCREMENT,
login varchar(20) NOT NULL,
password varchar(20) NOT NULL,
connectionNumber int NOT NULL DEFAULT 0
);
CREATE TABLE T_Roles (
idRole int PRIMARY KEY AUTO_INCREMENT,
roleName varchar(20) NOT NULL
);
CREATE TABLE T_Users_Roles_Associations (
idUser int NOT NULL REFERENCES T_Users(idUser),
idRole int NOT NULL REFERENCES T_Roles(idRole)
);

2. @Entity @Table(name="T_Users")
public class User {
@Id @GeneratedValue(strategy=GenerationType.IDENTITY)
private int idUser;
private String login;
private String password;
private int connectionNumber;
@ManyToMany @JoinTable( name = "T_Users_Roles_Associations", joinColumns =
@JoinColumn( name = "idUser" ), inverseJoinColumns = @JoinColumn( name = "idRole"
) )
private List<Role> roles = new ArrayList<>();
//constructeur
//getters et setters
}

3. @Entity @Table(name="T_Roles")
public class Role {
@Id @GeneratedValue(strategy=GenerationType.IDENTITY)
private int idRole;
private String roleName;
@ManyToMany @JoinTable( name = "T_Users_Roles_Associations", joinColumns =
@JoinColumn( name = "idRole" ), inverseJoinColumns = @JoinColumn( name =
"idUser" ) )
private List<User> users = new ArrayList<>();
//constructeur
//getters et setters
}