如何验证数据库中用户名的可用性? [英] How to validate availability of username in database?

问题描述

如果根据数据库可用，如何验证输入文本中的用户名?我正在使用JSF2.

How can I validate the entered username in an input text field if it is available according to the database? I am using JSF2.

推荐答案

只需实现

Just implement a Validator yourself.

@ManagedBean
@RequestScoped
public class UserNameAvailableValidator implements Validator {

    @EJB
    private UserService userService;

    @Override
    public void validate(FacesContext context, UIComponent component, Object value) throws ValidatorException {
        String userName = (String) value;

        if (!userService.isUsernameAvailable(userName)) {
            throw new ValidatorException(new FacesMessage("Username not avaliable"));
        }
    }

}

(请注意，它是一个@ManagedBean而不是@FacesValidator，因为需要注入一个@EJB；如果您不使用EJB，则可以将其设置为@FacesValidator)

(please note that it's a @ManagedBean instead of @FacesValidator because of the need to inject an @EJB; if you're not using EJBs, you can make it a @FacesValidator instead)

按以下方式使用它:

<h:inputText id="username" value="#{register.user.name}" required="true">
    <f:validator binding="#{userNameAvailableValidator}" />
    <f:ajax event="blur" render="username_message" />
</h:inputText>
<h:message id="username_message" for="username" />

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