@Entity
@Table(name ="client")
@NamedQuery(name="Client.getAll", query = "SELECT c FROM Client c")
public class Client {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
public  Long id;

@Column(name="first_name", length = 25)
private String firstName;

@Column(name="surname", length = 25)
private String surName;

@Column(name="password", length = 30)
private String password;
@Column(name="email")
private String email;

public void add(Client client){
    em.getTransaction().begin();
    em.persist(client);
    em.getTransaction().commit();

}
    public List<Client> findClientByEmail(String email){
    return em.createQuery(
            "SELECT  c FROM Client  c WHERE c.email LIKE :custEmail")
            .setParameter("custEmail", email)
            .setMaxResults(1)
            .getResultList();
}

public Client login(ClientDTO clientDTO){
    List<Client> clientList;
    clientList = clientDAO.findClientByEmail(clientDTO.getEmail());
    validLogin(clientList);
    Client client = clientList.get(0);
    validLogin(clientDTO, client);
    return client;
}

<persistence-unit name="Vlad" transaction-type="RESOURCE_LOCAL">
    <provider>org.hibernate.ejb.HibernatePersistence</provider>

    <properties>
        <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>
        <property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/clients"/>
        <property name="hibernate.connection.username" value="root"/>
        <property name="hibernate.connection.password" value="root"/>
        <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/>
        <property name="hibernate.hbm2ddl.auto" value="update"/>
    </properties>
</persistence-unit>