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Problem opening GRIB dataset using netCDF-Java

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  • Subject: Problem opening GRIB dataset using netCDF-Java
  • Date: Tue, 17 Sep 2013 23:56:43 +0000
John,

A Panoply user has been having trouble opening a GRIB dataset due to an
exception thrown from somewhere inside the NJ library. The exception is
caught and re-thrown by NetcdfFile.open(), but further tracing reveals
something going on when Gri1IOSP tries to open the file.

java.io.IOException: java.lang.IllegalArgumentException: Attribute value cannot 
be null
        at ucar.nc2.NetcdfFile.open(NetcdfFile.java:425)
        at 
ucar.nc2.dataset.NetcdfDataset.openOrAcquireFile(NetcdfDataset.java:699)
        at ucar.nc2.dataset.NetcdfDataset.openDataset(NetcdfDataset.java:421)
        at ucar.nc2.dataset.NetcdfDataset.acquireDataset(NetcdfDataset.java:516)
        at ucar.nc2.dataset.NetcdfDataset.acquireDataset(NetcdfDataset.java:493)
        at gov.nasa.giss.netcdf.NcDataset.init(NcDataset.java:118)
        ... more
Caused by: java.lang.IllegalArgumentException: Attribute value cannot be null
        at ucar.nc2.Attribute.setStringValue(Attribute.java:508)
        at ucar.nc2.Attribute.<init>(Attribute.java:370)
        at ucar.nc2.grib.grib1.Grib1Iosp.addGroup(Grib1Iosp.java:338)
        at ucar.nc2.grib.grib1.Grib1Iosp.open(Grib1Iosp.java:160)
        at ucar.nc2.NetcdfFile.<init>(NetcdfFile.java:1521)
        at ucar.nc2.NetcdfFile.open(NetcdfFile.java:813)
        at ucar.nc2.NetcdfFile.open(NetcdfFile.java:422)
        ... 16 more

I'm at a loss as to what to tell the user, as there's no further info
presented about what attribute it is that has a null value. It would
be of some help if the exception would also report the name/key of the
problem attribute.

A copy of the dataset is currently at

http://www.giss.nasa.gov/staff/rschmunk/data/20130917_153410_.grb

BTW: I commented last March that I had been having since the
start of the year with GRIB temporary files popping up in the same
directory as the GRIB file rather than in the cache dir specified by
DiskCache.setRootDirectory(). I thought this was "fixed" in 4.3.18 but
that was mistaken. On further exploration today, I found that a deliberate
change was made in 4.3.15, as described at

http://www.unidata.ucar.edu/software/thredds/current/netcdf-java/reference/Caching.html

However, although that webpage states that as of 4.3.15 one should use
Disk Cache2 class to deal with GRIB files, the section terminates before
providing an example of the DiskCache2 options. I did find an example
in the source code for the TestGribDiskCache class which gave me the
help I needed.


Thanks,
rbs
--
Robert B. Schmunk
Webmaster / Senior Systems Programmer
NASA Goddard Institute for Space Studies
2880 Broadway, New York, NY 10025