java - 如何验证 JSF 中的唯一性并向用户发送消息？

Question

我需要检查应用程序中字段的唯一性。

我尝试使用 Hibernate @Unique 约束，但它显示了堆栈跟踪，但用户表单中没有错误消息。

我的下一个解决方案是编写一个自定义 validator ，但我认为有更好的解决方案。

在 JSF 中是否有更简单的方法来做到这一点？

(JSF 2.1 + RichFaces)

Answer 1

我为我的基本实体的 JSF 2.1 唯一 key 验证破解了一个快速但肮脏的工作解决方案:

用法:

<p:inputText id="name" value="#{employeesController.currentEmployee.name}">
    <f:validator validatorId="uniqueColumnValidator" />
    <f:attribute name="currentEntity" value="#{employeesController.currentEmployee}" />
    <f:attribute name="uniqueColumn" value="name" />
</p:inputText>

validator :

@RequestScoped
@FacesValidator("uniqueColumnValidator")
public class UniqueColumnValidator implements Validator, Serializable {

    @PersistenceContext
    protected EntityManager em;

    /**
     * generic unique constraint validator for AbstractBaseEntity entities<br />
     * requires the following additional attributes on the form element ("<f:attribute>"):<br />
     * - "currentEntity" the entity instance (used for getting the class and guid)<br />
     * - "uniqueColumn" the column where the new value will be checked for uniqueness
     */
    @Override
    public void validate(final FacesContext context, final UIComponent comp, final Object newValue) throws ValidatorException {

    AbstractBaseEntity currentEntity = (AbstractBaseEntity) comp.getAttributes().get("currentEntity");
    String uniqueColumn = (String) comp.getAttributes().get("uniqueColumn");

    boolean isValid = false;
    try {
        em.createQuery(
                "FROM " + currentEntity.getClass().getSimpleName()
                + " WHERE " + uniqueColumn + " = :value"
                + " AND guid <> :guid", currentEntity.getClass())
                .setParameter("value", value)
                .setParameter("guid", currentEntity.getGuid())
                .getSingleResult();
    } catch (NoResultException ex) {
        isValid = true; // good! no result means unique validation was OK!
    }

    if (!isValid) {
        FacesMessage msg = Messages.createError("must be unique", uniqueColumn);
        context.addMessage(comp.getClientId(context), msg);
        throw new ValidatorException(msg);
    }
    }
}