java writeMetadata

James_Bullard · October 28, 2010, 5:25pm

Hi All,

The documentation for writeMetadata (java hdf5 API) states that if the
object exists it overwrites its value, however I am observing that if
the object exists it throws an exception and the same code works fine if
the object doesn't exist.

Am I in err?

thanks, jim

Peter_Cao · October 28, 2010, 6:41pm

Hi Jim,

hdf-java unit tests show fine for overwriting attribute values.
Could you send us some example code?

Thanks
--pc

···

On 10/28/2010 12:25 PM, James Bullard wrote:

Hi All,

The documentation for writeMetadata (java hdf5 API) states that if the
object exists it overwrites its value, however I am observing that if
the object exists it throws an exception and the same code works fine if
the object doesn't exist.

Am I in err?

thanks, jim

_______________________________________________
Hdf-forum is for HDF software users discussion.
Hdf-forum@hdfgroup.org
http://mail.hdfgroup.org/mailman/listinfo/hdf-forum_hdfgroup.org

Peter_Cao · October 28, 2010, 10:21pm

Hi Jim,

The reason for the failure was that you were trying to write a new attribute
to a dataset where an attribute with the name already exists.

If your want to update the values of an attribute, the correct way is to get
the attribute from the object, change the values, and write the attribute
back to the object.

The following example code creates a new dataset and adds an attribute to
the dataset. Then close the file and update the attribute that is attached to the
dataset.

Hope it helps.

Thanks
--pc

···

=====================
     private static void testUpdateAttr(String fname) throws Exception
     {
         int data[] = {1,2,3,4,5,6};
         long[] dims = {data.length};
         String dname = "/dset";

         // create a new file and a new dataset
         H5File file = new H5File(fname, FileFormat.CREATE);
         Datatype dtype = file.createDatatype(Datatype.CLASS_INTEGER, 4, Datatype.NATIVE, Datatype.NATIVE);
         Dataset dataset = file.createScalarDS (dname, null, dtype, dims, null, null, 0, data);

         // create and write an attribute to the dataset
         long[] attrDims = {2};
         int[] attrValue = {0, 10000};
         Attribute attr = new Attribute("range", dtype, attrDims);
         attr.setValue(attrValue); // set the attribute value
         dataset.writeMetadata(attr);

// close the file
file.close();

// open the file with read and write access
file = new H5File(fname, FileFormat.WRITE);

         // retrieve the dataset and attribute
         dataset = (Dataset)file.get(dname);
         attr = (Attribute)dataset.getMetadata().get(0);

         // change the attribute value
         if (attr!=null) {
             attrValue[0] = 100;
             attr.setValue(attrValue);

dataset.writeMetadata(attr);
}

         // close file resource
         file.close();
     }

On 10/28/2010 12:25 PM, James Bullard wrote:

Hi All,

The documentation for writeMetadata (java hdf5 API) states that if the
object exists it overwrites its value, however I am observing that if
the object exists it throws an exception and the same code works fine if
the object doesn't exist.

Am I in err?

thanks, jim

_______________________________________________
Hdf-forum is for HDF software users discussion.
Hdf-forum@hdfgroup.org
http://mail.hdfgroup.org/mailman/listinfo/hdf-forum_hdfgroup.org

java writeMetadata

// close file resource file.close(); }

// close file resource
file.close();
}