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Re: NullPointerException during aggregation

Hello-
I was about to ask the same question.
To expand on your problem, when aggregating 8 files, I encounter the error only when accessing the last file. That is, an ncdump in time of 0:6:1 has no error, but 0:7:1 causes the error. Thinking the eighth file was the problem, I removed it and got the error when accessing the last file again. It appears that there is some problem when trying to access the last file in the aggregation? Funny thing is the last file is being read properly (at least in part) because the time variable is properly assigned by grabbing it from all 8 files, but any of the other variables from the 8th file causes problems. 
-Ken Knapp

NCML file:

<netcdf xmlns="http://www.unidata.ucar.edu/namespaces/netcdf/ncml-2.2";>
 <aggregation dimName="time" type="joinExisting">
   <scan location="/home/kknapp/java/data/" suffix=".GPC"/>
 </aggregation>
</netcdf>



Jon Blower wrote:

Hi all,

I'm having problems working with NcML aggregations and the 2.2.16
version of the Java NetCDF libraries.  I would like to aggregate
files:

NATL_1_28082006.nc
NATL_1_29082006.nc
NATL_1_30082006.nc
...

along the time dimension.  I tried an NcML file like this:

<netcdf xmlns="http://www.unidata.ucar.edu/namespaces/netcdf/ncml-2.2";>
  <aggregation dimName="time" type="joinNew">
    <variableAgg name="temperature"/>
    <variableAgg name="salinity"/>
    <scan location="/path/to/files/" suffix=".nc"
dateFormatMark="NATL_1_#ddMMyyyy" />
  </aggregation>
</netcdf>

This gave me a NullPointerException:

java.lang.NullPointerException
    java.util.Calendar.setTime(Calendar.java:1032)
    java.text.SimpleDateFormat.format(SimpleDateFormat.java:785)
    java.text.SimpleDateFormat.format(SimpleDateFormat.java:778)
    java.text.DateFormat.format(DateFormat.java:314)
ucar.nc2.units.DateFormatter.toDateTimeStringISO(DateFormatter.java:184) 
    ucar.nc2.ncml.Aggregation.crawlDirectory(Aggregation.java:817)

I think I know why this is.  There are other files in the same
directory of the form "NATL_120_28082006.nc" and I think the
aggregator is trying to match these.  Can I arrange it so that only
files that match the pattern "NATL_1_#ddMMyyyy.nc" are aggregated, and
all others are simply ignored?

I am reluctant to change the directory structure of my data because
other applications may depend on it.

Thanks in advance,
Jon



--
Ken Knapp, Ph.D.      address@hidden
Remote Sensing and Applications Division
National Climatic Data Center
151 Patton Ave
Asheville, NC 28801-5001
828-271-4339 (voice) 828-271-4328 (fax)

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