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INexusDevice (h5jan API)
org.eclipse.dawnsci.nexus
Interface INexusDevice<N extends NXobject>
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- Type Parameters:
N - the type of nexus object to be created, a sub-interface of NXobject,
e.g. NXdetector
public interface INexusDevice<N extends NXobject>
Any device which can write NeXus should implement this interface.
This can be done easily by extending AbstractNexusObjectProvider
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Method Summary
All Methods Instance Methods Abstract Methods Default Methods
Modifier and Type
Method and Description
default CustomNexusEntryModificationgetCustomNexusModification()
Returns an object that performs a custom modification to
an NXentry.
NexusObjectProvider<N>getNexusProvider(NexusScanInfo info)
Returns the object provider required for writing correct NeXus files.
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Method Detail
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getNexusProvider
NexusObjectProvider<N> getNexusProvider(NexusScanInfo info)
throws NexusException
Returns the object provider required for writing correct NeXus files.
In this method you should prepare the LazyDatasets the device
will fill during the scan. You can also write out static device metadata,
which will not change during the scan.
Use the methods on NexusNodeFactory to create a NeXus object which
matches the device e.g. a NXdetector.
final NXdetector detector = NexusNodeFactory.createNXdetector();
On the detector object you can create LazyDatasets and keep
references which you can later use during the scan to write data. e.g.
imageData = detector.initializeLazyDataset(NXdetector.NX_DATA, info.getRank() + 2, Dataset.FLOAT64);
You should also set chunking on the LazyDatasets you create e.g. imageData.setChunking(info.createChunk(detectorXSize, detectorYSize));.
In this method you can also write static metadata such as the detector
exposure e.g.
detector.setField("exposure_time", model.getExposure());. Or
static datasets such as the image axis data
detector.setDataset("image_x_axis", DatasetFactory.createLinearSpace(minX, maxX, xPoints, Dataset.FLOAT64));
For fields that are defined in the NXDL base class definition for the
returned nexus object, a setXXX or setXXXScalar method may be used as
appropriate, e.g. detector.setLocalName(DatasetFactory.createFromObject("my detector"));
or detector.setLocalNameScalar("my detector");
If this device is a 'metadata scannable', then the device should write
its data at this point directly into the returned nexus object. This can be
done with the NXobject.setField(String, Object) method, or the
setXXXScalar methods for fields defined in the appropriate
NXDL base class definition.
- Parameters:
info - Information about the scan which can be useful when creating
dataset e.g. info.getRank()- Returns:
- The
NXobject created using the nodeFactory
to represent this device
- Throws:
NexusException - if the nexus object could not be created for any reason
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getCustomNexusModification
default CustomNexusEntryModification getCustomNexusModification()
Returns an object that performs a custom modification to
an NXentry.
NOTE: Use this method with caution as it can be used to break the central
design concept of the new Nexus writing framework, namely that the nexus framework itself
knows where to put the nexus groups for devices and build any required NXdata groups.
It is currently used by the new Nexus framework to partially support legacy GDA8 spring
configurations, in particular the 'locationmap'.
The nexus framework will call this method after #createNexusObject(NexusNodeFactory, NexusScanInfo),
so this method create links to nodes created in that method if appropriate.
The easiest way to implement this method is to make this object itself also implement
CustomNexusEntryModification. This method can then be overridden to simply
return this.
- Returns:
- a
CustomNexusEntryModification that makes a custom modification,
or null if this device should not make custom modifications