Friday, July 10, 2015

Drag-and-Drop support in Spoon

If you've ever played around with Drag-n-Drop in Spoon, you probably know that you can drag a KTR, KJB, or XML file onto the canvas, and it will open that file (if a legal PDI artifact) in Spoon for editing.  Under the hood, this is accomplished with "FileListeners", there are transformation and job versions of listeners registered automatically at Spoon startup.

However, did you know you can register your own FileListeners?  There is a pretty straightforward interface:

public interface FileListener {

  public boolean open( Node transNode, String fname, boolean importfile ) throws KettleMissingPluginsException;

  public boolean save( EngineMetaInterface meta, String fname, boolean isExport );

  public void syncMetaName( EngineMetaInterface meta, String name );

  public boolean accepts( String fileName );

  public boolean acceptsXml( String nodeName );

  public String[] getSupportedExtensions();

  public String[] getFileTypeDisplayNames( Locale locale );

  public String getRootNodeName();
}

You can implement this interface and it will be called at various points, including when a file is dragged onto the canvas. You can use this to add support to currently unsupported file types.  I will show how I implemented a quick CsvListener to add drag-and-drop support to PDI. With this, if you drag a CSV file onto a transformation on the canvas, a "CSV file input" step will be added to the transformation, with the filename already filled in:



I didn't bother with doing a "Get Fields" automatically because I won't know if there's a header row, etc.  Plus this is just a fun proof-of-concept, hopefully I/we will have a more robust Drag-n-Drop system in the future.

The trick is getting your FileListener registered with Spoon. There is no extension point directly for that purpose, but you can use a LifecycleListener plugin and implement the registration in your onStart() callback.

To get this going quickly, I wrote the CsvListener in Groovy, and put that in a file called onStart.groovy. I did that so I could leverage my PDI Extension Point Scripting plugin (available on the Marketplace), then drop my onStart.groovy file into plugins/pdi-script-extension-points/ and start Spoon.

The Groovy script is as follows, and is also available as a Gist:

import org.w3c.dom.* import org.pentaho.di.core.* import org.pentaho.di.core.exception.* import org.pentaho.di.core.gui.* import org.pentaho.di.core.plugins.* import org.pentaho.di.trans.step.* import org.pentaho.di.ui.spoon.* class CsvListener implements FileListener { public boolean open( Node transNode, String fname, boolean importfile ) throws KettleMissingPluginsException { def csvInputPlugin = PluginRegistry.instance.findPluginWithName(StepPluginType, 'CSV file input') def csvInputMetaClass = PluginRegistry.instance.loadClass(csvInputPlugin) csvInputMetaClass.setDefault() def pid = PluginRegistry.instance.getPluginId(csvInputPlugin.pluginType, csvInputMetaClass) def csv = new StepMeta(pid, csvInputPlugin.name, csvInputMetaClass) csv.stepMetaInterface.setFilename(fname) csv.setName(fname?.substring(fname?.lastIndexOf(File.separator)+1,fname?.indexOf('.')) ?: 'CSV file input') csv?.location= new Point(20,20) csv?.draw = true Spoon.instance.activeTransformation?.addStep(csv) Spoon.instance.activeTransGraph?.redraw() true } public boolean save( EngineMetaInterface meta, String fname, boolean isExport ) { false } public void syncMetaName( EngineMetaInterface meta, String name ) { } public boolean accepts( String fileName ) { def x = Arrays.asList(getSupportedExtensions()).contains(fileName?.substring(fileName?.indexOf('.')+1)) } public boolean acceptsXml( String nodeName ) { false } public String[] getSupportedExtensions() { ['csv'] as String[] } public String[] getFileTypeDisplayNames( Locale locale ) { ['CSV'] as String[] } public String getRootNodeName() { null } } Spoon.instance.addFileListener(new CsvListener())
There's lots of PDI voodoo going on in the open() method; I won't explain it all here, as I intend to write a proper plugin to do this for various file types. I just wanted to (again) show off how powerful and flexible PDI can be, and have some fun hacking the APIs :)

Cheers!