Facebook4j - get access and post to different groups

Question

I have a question regarding facebook4j API for Java. I would like to have the following: - I have a webapp with different user - Each user can post with his Facebook Account to different groups - This means I have to store from every user the different API Keys - The Key should not expire, is this possible?

Here a sample code for get access:

public class LoginFacebook {

public static String appId = "myAppId";   // Sample values
public static String appSecret = "myAppSecret";
public static String access_token = "myToken";

public static Facebook facebook;

public RecuperationFacebook() {
    facebook = new FacebookFactory().getInstance();
    facebook.setOAuthAppId(appId, appSecret);
    facebook.setOAuthAccessToken(new AccessToken(access_token));
}

public static Comment Commentaire(String id_comment) throws FacebookException {
    Comment commentaire =facebook.getComment(id_comment, null);
    return(commentaire);
}

}

Question: - How get every user his API Key? - What are the different API Keys? (appId, appSecret, access_token) ?

Many thanks for help