@Entity
@NamedQueries({ @NamedQuery(name = "Product.findAll", query = "select o from Product o") })
@Table(name = ""product"")
public class Product implements Serializable {
    private static final long serialVersionUID = 692860634577894848L;
    @Id
    @Column(name = "idProduct", nullable = false)
    private int idProduct;
    @Column(name = "p_name", nullable = false)
    private String p_name;
    @ManyToOne(fetch=FetchType.LAZY)
    @JoinColumn(name = "idType")
    private Type type;
    @ManyToOne(fetch=FetchType.LAZY)
    @JoinColumn(name = "idManufacturer")
    private Manufacturer manufacturer;
    @ManyToOne(fetch=FetchType.LAZY)
    private Users users;
 
    public Product() {
    }
 
    public Product(Manufacturer manufacturer, int idProduct, Type type, String p_name,Users users) {
        this.manufacturer = manufacturer;
        this.idProduct = idProduct;
        this.type = type;
        this.p_name = p_name;
        this.users = users;
    }
 
 
    public int getIdProduct() {
        return idProduct;
    }
 
    public void setIdProduct(int idProduct) {
        this.idProduct = idProduct;
    }
 
 
    public String getP_name() {
        return p_name;
    }
 
    public void setP_name(String p_name) {
        this.p_name = p_name;
    }
 
    public Type getType() {
        return type;
    }
 
    public void setType(Type type) {
        this.type = type;
    }
 
    public Manufacturer getManufacturer() {
        return manufacturer;
    }
 
    public void setManufacturer(Manufacturer manufacturer) {
        this.manufacturer = manufacturer;
    }
 
    public Users getUsers() {
        return users;
    }
 
    public void setUsers(Users users) {
        this.users = users;
    }
}

....
List<Product> product = sel.getProductFindAll();
for (int i = 0; i < product.size(); i++) {
    out.println(product.get(i).getP_name());
}
....

javax.ejb.EJBException: EJB Exception: : javax.persistence.PersistenceException: Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown column 'USERS_idUsers' in 'field list'
Error Code: 1054
Call: SELECT idProduct, p_name, idManufacturer, idType, USERS_idUsers FROM `product`
Query: ReadAllQuery(name="Product.findAll" referenceClass=Product sql="SELECT idProduct, p_name, idManufacturer, idType, USERS_idUsers FROM `product`")