Find user by authentication token in Rails?

So for a certain project I'm thinking it may possibly be useful for me to be able to take an authentication token and figure out which user it is for. I'm not sure if it's ev开发者_JAVA百科en possible or not. Anyone happen to know?

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Authlogic (example app linked) uses 'persistence tokens'.

    t.string    :login,               :null => false                # optional, you can use email instead, or both
    t.string    :email,               :null => false                # optional, you can use login instead, or both
    t.string    :crypted_password,    :null => false                # optional, see below
    t.string    :password_salt,       :null => false                # optional, but highly recommended
    t.string    :persistence_token,   :null => false                # required
    t.string    :single_access_token, :null => false                # optional, see Authlogic::Session::Params
    t.string    :perishable_token,    :null => false                # optional, see Authlogic::Session::Perishability

    # Magic columns, just like ActiveRecord's created_at and updated_at. These are automatically maintained by Authlogic if they are present.
    t.integer   :login_count,         :null => false, :default => 0 # optional, see Authlogic::Session::MagicColumns
    t.integer   :failed_login_count,  :null => false, :default => 0 # optional, see Authlogic::Session::MagicColumns
    t.datetime  :last_request_at                                    # optional, see Authlogic::Session::MagicColumns
    t.datetime  :current_login_at                                   # optional, see Authlogic::Session::MagicColumns
    t.datetime  :last_login_at                                      # optional, see Authlogic::Session::MagicColumns
    t.string    :current_login_ip                                   # optional, see Authlogic::Session::MagicColumns
    t.string    :last_login_ip                                      # optional, see Authlogic::Session::MagicColumns

It may not be exactly what you want, but I think you can make it work. The real question is, why do you want to do this?