<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        " http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>

        <property name="hibernate.connection.driver_class">com.mysql.cj.jdbc.Driver</property>
        <!--<property name="jdbc:mysql://localhost:3306/mydbtest"/>-->
        <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/mydbtest?autoReconnect=true&useSSL=false</property>
        <property name="hibernate.connection.username">root</property>
        <property name="hibernate.connection.password">root</property>
        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
        <property name="show_sql">true</property>
        <property name="hibernate.hbm2ddl.auto">create</property>

        <mapping resource="user.cfg.xml"/>
    </session-factory>
</hibernate-configuration>

public class User {

    private int id;
    private String firstname;
    private String lastname;
    private int age;

    public User() {
    }

    public User(int id) {
        this.id = id;
    }


    public void setId(int id) {
        this.id = id;
    }

    public int getId() {
        return id;
    }

    public String getFirstname() {
        return firstname;
    }

    public void setFirstname(String firstname) {
        this.firstname = firstname;
    }

    public String getLastname() {
        return lastname;
    }

    public void setLastname(String lastname) {
        this.lastname = lastname;
    }

    public int getAge() {
        return age;`введите сюда код`
    }

    public void setAge(int age) {
        this.age = age;
    }
}