[netcdf-java] Possibility for per-dataset http client?

• To: netcdf-java <netcdf-java@xxxxxxxxxxxxxxxx>
• Subject: [netcdf-java] Possibility for per-dataset http client?
• From: "Jon Blower" <j.d.blower@xxxxxxxxxxxxx>
• Date: Mon, 19 Jan 2009 16:03:25 +0000

Hi,

Accessing OPeNDAP or remote NetCDF files in nj4.0 uses the Apache
Commons HttpClient library.  If my understanding is correct then nj4.0
uses the same HttpClient instance for all connections, and this
instance is set with static methods:

        opendap.dap.DConnect2.setHttpClient(client);
        ucar.unidata.io.http.HTTPRandomAccessFile.setHttpClient(client);

In my case, I have a Java web application (running in a single VM)
accessing lots of remote servers via HTTP.  The entire application
uses the same HttpClient instance, and therefore there is no way to
distinguish between the users of my application.  Say I have two users
going via my application to the same secure OPeNDAP server.  My
application can only associate a *single* username/password
combination with the host:port of the OPeNDAP server, following the
Credentials framework in HttpClient.  There is no way to register two
different username/password combinations for the same remote server.

One possible way to fix this would be to allow each NetcdfDataset to
be associated with its own HttpClient instance.  This could be
provided as an optional parameter to openDataset(), defaulting back to
the VM-wide one if omitted.  Then I could store an HttpClient (with
associated credentials) in the user's session object in my
application.  (I am not sure if this is good practice for HttpClient
though.)

Is this easily remedied or a tough job?

Cheers, Jon

-- 
Dr Jon Blower
Technical Director, Reading e-Science Centre
Environmental Systems Science Centre
University of Reading
Harry Pitt Building, 3 Earley Gate
Reading RG6 6AL. UK
Tel: +44 (0)118 378 5213
Fax: +44 (0)118 378 6413
j.d.blower@xxxxxxxxxxxxx
http://www.nerc-essc.ac.uk/People/Staff/Blower_J.htm

• Follow-Ups:
  • Re: [netcdf-java] Possibility for per-dataset http client?
    • From: John Caron