Alter table dinamico

@Entity(name = "tb_custom_field")
@NamedQueries({ @NamedQuery(name = "CustomField.findAll", query = "SELECT cf FROM tb_custom_field cf"), })
public class CustomField implements Serializable {

	private static final long serialVersionUID = 1L;

	@Id
	@Column(name = "custom_field_id")
	@GeneratedValue(strategy = GenerationType.AUTO, generator = "seq_tb_custom_field_custom_field_id")
	@SequenceGenerator(name = "seq_tb_custom_field_custom_field_id", sequenceName = "seq_tb_custom_field_custom_field_id", allocationSize = 1)
	private long id;

	@Column(name = "custom_field_name", nullable = false)
	private String name;

	@Column(name = "custom_field_description", nullable = false)
	private String description;

	@Column(name = "custom_field_type", nullable = false)
	private String type;

	@Column(name = "custom_field_system", nullable = false)
	private boolean system;
	
	@Column(name="custom_field_required" ,nullable=false, columnDefinition="boolean default false")
	private boolean required;

	public boolean isRequired() {
		return required;
	}

	public void setRequired(boolean required) {
		this.required = required;
	}

	public long getId() {
		return id;
	}

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

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getDescription() {
		return description;
	}

	public void setDescription(String description) {
		this.description = description;
	}

	public String getType() {
		return type;
	}

	public void setType(String type) {
		this.type = type;
	}

	public boolean isSystem() {
		return system;
	}

	public void setSystem(boolean system) {
		this.system = system;
	}
}

session.createSQLQuery("ALTER TABLE tb_customer ADD COLUMN " + customerField.getName() + " varchar(250)").executeUpdate();

public class CustomFieldFacade {

	private CustomField customField;
	private List<CustomField> customFields;

	public CustomField getCustomField() {
		return customField;
	}

	public void setCustomField(CustomField customField) {
		this.customField = customField;
	}

	public List<CustomField> getCustomFields() {
		return customFields;
	}

	public void setCustomFields(List<CustomField> customFields) {
		this.customFields = customFields;
	}
	
	public void save(CustomField customerField) {
		EntityManager em = JPAUtil.getEntityManager();
		setCustomField(em.merge(customerField));
		
		Session session = null;
		try {
			session = (Session) em.getDelegate();
	        session.createSQLQuery("ALTER TABLE tb_customer ADD COLUMN " + customerField.getName() + " varchar(250)").executeUpdate();
		} catch(Exception e) {
			
		}
	}

	public CustomField alter(CustomField customerField) {
		setCustomField(CustomFieldDAO.find(customerField));
		return getCustomField();
	}

	public void delete(CustomField customerField) {
		EntityManager em = JPAUtil.getEntityManager();
		setCustomField(CustomFieldDAO.find(customerField));
		CustomField ref = CustomFieldDAO.find(customerField);
		em.remove(ref);
	}

	public List<CustomField> datagrid() {
		return CustomFieldDAO.getListCustomField();
	}
}