3. Connecting to Hydra Platform

To start the Plugin, we create an ExportJSON class which will do our work for us.

The constructor of this class, __init__ takes two arguments: a URL and a session_id. The url tells the plugin where Hydra Platform is. If this is left as None, a default is found in config.

The second parameter is session_id. If a user is already connected to Hydra, (through Hydra Modeller) they already have a session ID. By passing their existing session ID into the plugin, there is no need for the user to log in again.

The connection is created by creating a new JsonConnection object, passing in the url and then calling login if necessary. This can take a username and password, but if not provided, these details are fetched from config.

Finally self.num_steps is defined. This simply allows us to keep track of how many steps there are in the plugin, so that we can use it as a way to display to the user at what point in the process the plugin is currently operating.

class ExportJSON(object):
    """
       Exporter of Hydra networks to JSON or XML files.
    """
    def __init__(self, url=None, session_id=None):

        #Record the names of the files created by the plugin so we can
        #display them to the user.
        self.files    = []

        self.connection = JsonConnection(url)
        write_output("Connecting...")
        if session_id is not None:
            log.info("Using existing session %s", session_id)
            self.connection.session_id=session_id
        else:
            self.connection.login()

        self.num_steps = 3