what is access_token ,what is purpose of usage or what is it used for? [duplicate]

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Possible Duplicate:

How's the current state of Facebook's session and access_token?

I am using facebook sdk v3.0 to develop facebook applications. Could you answer following questions for me ;

1) what is access_token 开发者_如何学编程? 2) Is it required to store ID of access_token in database with user id ? 3) Has access_token specified life time ?

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Ahem.

• As for #1 ("What is an access_token?"), a single search has brought forth http://developers.facebook.com/docs/authentication/ (y'know, the official documentation page for the platform you're developing for, hint hint), which says:

App authentication ensures that the user is giving their information to your app and not someone else. Once these steps are complete, your app is issued an user access token that you enables you to access the user's information and take actions on their behalf.

• As for #3 ("Does an access_token have a specified lifetime?") , the very same page says:

In addition to the access token (the access_token parameter), the response contains the number of seconds until the token expires (the expires parameter). Once the token expires, you will need to re-run the steps above to generate a new code and access_token [...]

• As for #2, it follows that an access token is temporary, and thus you don't need to store it permanently.