ciao
ho fatto una piccola prova creando una tabella con un campo auto_increment (posto sotto il codice autogenerato dell'entità)... il problema è che se non gli setto io manualmente l'ID e vado a fare la persist dell'oggetto comprensivo di tutti i campi mi genera una ejb.exception....
non riesco a capire proprio quale siaaa... per una stupidata del genereee devo impazziree!
dove stà il problema secondo voi?

codice:
/*
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 * and open the template in the editor.
 */
package entity2;

import java.io.Serializable;
import javax.persistence.Basic;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.Table;
import javax.validation.constraints.NotNull;
import javax.validation.constraints.Size;
import javax.xml.bind.annotation.XmlRootElement;

/**
 *
 * @author Flaka
 */
@Entity
@Table(name = "Login")
@XmlRootElement
@NamedQueries({
    @NamedQuery(name = "Login.findAll", query = "SELECT l FROM Login l"),
    @NamedQuery(name = "Login.findById", query = "SELECT l FROM Login l WHERE l.id = :id"),
    @NamedQuery(name = "Login.findByUsername", query = "SELECT l FROM Login l WHERE l.username = :username"),
    @NamedQuery(name = "Login.findByPassword", query = "SELECT l FROM Login l WHERE l.password = :password"),
    @NamedQuery(name = "Login.findByValidato", query = "SELECT l FROM Login l WHERE l.validato = :validato")})
public class Login implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy= GenerationType.IDENTITY)
    @Basic(optional = false)
    @NotNull
    @Column(name = "Id")
    private Integer id;
    @Basic(optional = false)
    @NotNull
    @Size(min = 1, max = 45)
    @Column(name = "Username")
    private String username;
    @Basic(optional = false)
    @NotNull
    @Size(min = 1, max = 32)
    @Column(name = "Password")
    private String password;
    @Basic(optional = false)
    @Column(name = "Validato")
    private boolean validato=false;

    public Login() {
    }

    public Login(Integer id) {
        this.id = id;
    }

    public Login(Integer id, String username, String password, boolean validato) {
        this.id = id;
        this.username = username;
        this.password = password;
        this.validato = validato;
    }

    public Integer getId() {
        return id;
    }

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

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public boolean getValidato() {
        return validato;
    }

    public void setValidato(boolean validato) {
        this.validato = validato;
    }

    @Override
    public int hashCode() {
        int hash = 0;
        hash += (id != null ? id.hashCode() : 0);
        return hash;
    }

    @Override
    public boolean equals(Object object) {
        // TODO: Warning - this method won't work in the case the id fields are not set
        if (!(object instanceof Login)) {
            return false;
        }
        Login other = (Login) object;
        if ((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id))) {
            return false;
        }
        return true;
    }

    @Override
    public String toString() {
        return "entity2.Login[ id=" + id + " ]";
    }
    
}
grazie a tutti