James Gallagher wrote:
On Apr 14, 2005, at 9:12 PM, John Caron wrote:
Tennessee Leeuwenburg wrote:
Hi guys,
We're looking at phase two of the project I'm working on at the
moment. Phase one involved hooking up our weirdo database to
OpenDAP, and it looks that that will be a success. There's one thing
that's not as wonderful as we might hope, and a couple of cool extra
things we'd like to do.
In order to cope with observational data stored in BUFR format,
we've had to write scripts for conversion to NetCDF prior to serving
it with thredds. I don't really like messing about in thredds code
if I can help it, on account of it makes code maintainance that much
harder. So we convert to NetCDF on a product-by-product basis. But
it would be way cool if we could serve BUFR data more generally and
without the conversion step. So my question is : does anyone on this
list care much about BUFR data, and is anyone thinking much about
how it might fit into an OpenDAP context?
What kind of data is stored in BUFR?
We have an "I/O service provider" framework in netcdf-java version
2.2, where you can read non-native files as if they are netcdf files.
This sounds really cool! Does this work by subclassing some generic
access methods? This would make all sorts of one-off servers easy for
us to write.
James
Hi James:
It uses delegation rather than inheritence, but its the same result. The
"Service Provider" pattern is used extensively throughout the Java
libraries, to allow you to "plug in" services like security, storage
etc. In our case, a netcdf "I/O service provider" implements a small set
of methods, which the NetcdfFile object uses whenever it does any I/O.
The interface looks like:
public interface IOServiceProvider {
boolean isValidFile( RandomAccessFile raf);
void open( RandomAccessFile raf, NetcdfFile ncfile);
Array readData( Variable v2, List section);
// only if you use Structures
Array readNestedData( Variable v2, List section);
}
gory details as usual in the javadoc (see ucar.nc2.IOServiceProvider,
implementations live under ucar.nc2.iosp) :
http://www.unidata.ucar.edu/packages/netcdf-java/v2.2/javadoc/index.html
I am excited about the possibility of "one-off servers that are easy to
write". This will allow both local access and remote access via opendap.
I will write documentation (Real Soon Now) for anyone who wants to to
write one of these, in the meanwhile, any "early adopters" can get
special attention.
