如何使用Grails社交插件从Facebook获取电子邮件ID

我在我的应用程序中使用spring-security-oauth-facebook:0.1 grails插件.现在我想访问人的电子邮件ID,但我不能每次facebook服务器响应1829812989120 for socialId,Username,profileId并且没有电子邮件选项在返回Map对象时.为什么会发生这种情况.

     oauth {
        debug = true
           providers {
    facebook {
        api = org.scribe.builder.api.FacebookApi
        key = 'my-app-key'
        secret = 'secret-key'
        successUri = '/oauth/facebook/success'
        failureUri = '/oauth/facebook/failure'
        callback = "${baseURL}/oauth/facebook/callback"
        scopes = "['public_profile','email','name','user']"

      } 

    def sessionKey = oauthService.findSessionKeyForAccessToken(provider)

    if (!session[sessionKey]) {
        log.warn "No OAuth token in the session for provider '${provider}'"
        throw new OAuthLoginException("Authentication error for provider '${provider}'")
    }
    // Create the relevant authentication token and attempt to log in.

    OAuthToken oAuthToken = springSecurityOAuthService.createAuthToken(provider, 
                                                                            session[sessionKey])
    println "oAuthToken.principal = "+oAuthToken.principal.toString();
    println "oAuthToken.socialId  = "+oAuthToken.socialId;
    println "oAuthToken.properties= "+oAuthToken.properties
    println "oAuthToken.properties= "+oAuthToken.name
    println "oAuthToken.properties= "+oAuthToken.toString();

1)我ckecked所有println值电子邮件不存在.请帮我如何获取登录用户的电子邮件地址.