{"id":13220,"date":"2014-04-28T17:02:17","date_gmt":"2014-04-28T11:32:17","guid":{"rendered":"http:\/\/www.tothenew.com\/blog\/?p=13220"},"modified":"2014-04-28T20:40:24","modified_gmt":"2014-04-28T15:10:24","slug":"facebook-oauth-for-fetching-page-token","status":"publish","type":"post","link":"https:\/\/www.tothenew.com\/blog\/facebook-oauth-for-fetching-page-token\/","title":{"rendered":"Facebook Oauth for fetching page token"},"content":{"rendered":"

OAuth<\/a> is a secure mechanism to access facebook.<\/p>\n

To access facebook in your grails application you need to create a facebook app, go to https:\/\/developers.facebook.com<\/a>, click on Apps dropdown, further click on ‘Create a new App’.<\/p>\n

Ensure that you register the URL of you application with the Facebook app you have setup.<\/p>\n

Save your apiKey and secretKey provided by Facebook.<\/p>\n

We are going to use Scribe<\/a> java library for Oauth authentication.<\/p>\n

Add this to your BuildConfig.groovy for integrating Scribe.<\/p>\n

[java]<\/p>\n

compile ‘org.scribe:scribe:1.3.5’<\/p>\n

[\/java]<\/p>\n

Create a controller, lets call it Demo Controller and define some variables in it.<\/p>\n

[java]<\/p>\n

class DemoController {
\n String apiKey = \u201cxxxxxxxxxxxxxxx\u201d
\n String secretKey = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
\n String baseUrl = "https:\/\/graph.facebook.com\/";
\n String callbackUrl = \u201c\/demo\/action2\u201d \/\/ link to the callback url of your application
\n String fbUserToken \/\/ we will get value for this later
\n String pageToken \/\/ we will get value for this later
\n}<\/p>\n

[\/java]<\/p>\n

Now create an action using which we will initiate the Oauth flow<\/p>\n

[java]<\/p>\n

def index() {
\n OAuthService service = new ServiceBuilder()
\n .provider(FacebookApi.class)
\n .apiKey(apiKey)
\n .apiSecret(secretKey)
\n .scope("manage_pages,read_insights")
\n .callback(grailsApplication.config.grails.serverURL + callbackUrl)
\n .build();
\n String authUrl = service.getAuthorizationUrl(null);
\n redirect(url: authUrl.toURL())
\n}
\n[\/java]<\/p>\n

This action will initiate a call to Facebook Oauth and user will be redirected to a facebook login page. Upon successful authentication, the user will be redirected to the callback url of your application as specified by you. (\/demo\/action2 in this case).<\/p>\n

Here you will receieve authorization code in params. Which you can use to generate a short term token.<\/p>\n

[java]
\ndef action2() {
\n OAuthService service = new ServiceBuilder()
\n .provider(FacebookApi.class)
\n .apiKey(apiKey
\n .apiSecret(secretKey)
\n .scope("manage_pages,read_insights")
\n .callback(grailsApplication.config.grails.serverURL + callbackUrl)
\n .build();
\n Verifier v = new Verifier(params.code);
\n Token accessToken = service.getAccessToken(null, v); \/\/ returns short term token for FB User
\n fbUserToken = getLongTermUserToken(accessToken.token) \/\/ returns long term token for FB User which is valid for 2 months.
\n pageToken = getPageToken(longTermToken) \/\/ returns the long term token for the facebook page which has no expiry.
\n}
\n[\/java]<\/p>\n

Now we have a access token, using which we can make calls to facebook on behalf of user, however, this is only a short term token valid for period of about 10 mins. We can get a long term token using :<\/p>\n

[java]<\/p>\n

fbUserToken = getLongTermUserToken(accessToken.token) \/\/ returns long term token for FB User which is valid for 2 months.<\/p>\n

String getLongTermUserToken(String accessToken) {
\n String url = baseUrl + "oauth\/access_token?grant_type=fb_exchange_token&client_id=${apiKey}&client_secret=${apiSecret}&fb_exchange_token=${accessToken}"
\n URL longTermUrl=new URL(url)
\n String response = longTermUrl.text
\n String longTermToken = extractLongTermToken(response)
\n if (!longTermToken) {
\n throw new Exception("Some good exception while fetching Long term Token")
\n }
\n return longTermToken
\n}<\/p>\n

String extractLongTermToken(String response) {
\n List list = response.tokenize("&")
\n String result = ""
\n list.each { String s ->
\n if (s.startsWith("access_token")) {
\n result = s.tokenize("=").last()
\n }
\n }
\n return result
\n}
\n[\/java]<\/p>\n

Now we have a long term token, which is valid for about 2 months. However to retrieve page information of a page managed by user, we need another token known as page token. To get page token :<\/p>\n

[java]<\/p>\n

String getPageToken(String longTermToken) {
\n String url = baseUrl + "me\/accounts?access_token=${longTermToken}"
\n URL pageTokenUrl=new URL(url)
\n String dataString = pageTokenUrl.text
\n JSONObject data = JSON.parse(dataString)
\n Map response = data as Map
\n String pageToken = extractPageToken(response)
\n if (!pageToken) {
\n throw new Exception("Some good exception while fetching Page Token")
\n }
\n return pageToken
\n}<\/p>\n

String extractPageToken(Map response) {
\n String pageToken = ”
\n response.data.each {
\n if (it.id == pageId) {
\n pageToken = it.access_token
\n }
\n }
\n return pageToken
\n}<\/p>\n

[\/java]<\/p>\n

Notice that we are using long term access token to get the page token. A page token fetched using long term access token has no expiry date. Now we can use this page token to fetch information for the page like page insights etc.<\/p>\n

Hope it helps.<\/p>\n

Mansi Arora<\/p>\n

mansi[at]ntelligrape[dot]com<\/p>\n","protected":false},"excerpt":{"rendered":"

OAuth is a secure mechanism to access facebook. To access facebook in your grails application you need to create a facebook app, go to https:\/\/developers.facebook.com, click on Apps dropdown, further click on ‘Create a new App’. Ensure that you register the URL of you application with the Facebook app you have setup. Save your apiKey […]<\/p>\n","protected":false},"author":79,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"iawp_total_views":24,"footnotes":""},"categories":[7],"tags":[703,4840,770,1413,1414],"class_list":["post-13220","post","type-post","status-publish","format-standard","hentry","category-grails","tag-facebook","tag-grails","tag-oauth","tag-page-token","tag-scribe"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t