Grails Facebook插件 - 如何处理无效的用户 [英] Grails Facebook Plugin - How to Handle Invalid User

问题描述

我正在使用美妙的 Grails Facebook插件，事情正常。问题来自于我提供了另一种认证方式：表单认证。如果系统中已经有一个Facebook用户的电子邮件地址的用户，我想优雅的提醒用户这个事实。我不知道如何做，因为我被埋在一个从过滤器调用的服务。理想情况下，我想在登录页面上显示一条错误消息。这是可能的吗？

I am using the wonderful Grails Facebook Plugin and things are working alright. The problem comes from the fact that I provide another way to authenticate: forms authentication. If there is already a user in the system with the email address of the Facebook user, I would like to gracefully alert the user of this fact. I don't know how to do that since I am buried inside of a service which gets called from a Filter. Ideally I would like to show an error message on the login page. Is this possible?

我的 FacebookAuthService ：

    FacebookUser create(FacebookAuthToken token) {
    log.info("Create domain for facebook user $token.uid")

    Facebook facebook = new FacebookTemplate(token.accessToken.accessToken)
    FacebookProfile fbProfile = facebook.userOperations().userProfile
    String email = fbProfile.getEmail() 

    String emailMatch = User.findByEmailAddress(email)

    if(emailMatch != null)
        throw new RuntimeException("username is bad!!")

我想向用户显示此错误消息，而不是一直通过的异常。我该怎么做？谢谢！

I want to display this error message to the user instead of the exception trickling all the way through. How can I do this? Thanks!

推荐答案

您可以将此消息放入Flash对象中：

You can put this message into a flash object:

def grailsWebRequest = WebUtils.retrieveGrailsWebRequest()
def flash = grailsWebRequest.attributes.getFlashScope(request)
flash.error = "username is bad!!!"
return null // Facebook filter will skip authorization at this case

此外， code> RuntimeException 最好使用 AuthenticationException 的实例。在这种情况下，您可以将Spring Security配置为异常后重定向到特殊URL。只需放入 Config.groovy ：

Also, instead of RuntimeException it's better to use instance of AuthenticationException. At this case you can configure Spring Security to redirect to special url after exception. Just put into Config.groovy:

grails.plugins.springsecurity.failureHandler.exceptionMappings = [
   'MyException': '/usernameIsBad'
]

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