GigaSpaces VB API version 1.0 is now available under OpenSpaces.org.
Up and above some enhancements and stability fixes, the main addition in this release is native notification support for VBA applications.
The distribution includes a comprehensive example of notifications, which includes also (as a side effect) interoperability with Java. It is a simulation of FXSpot Pricing System in which prices are updated by an external system (the Java feeder in our case), and at the other end there is a spreadsheet which is listening to the FXSpot updates.
Here are the basics of the example:
FXSpot POJO:
@SpaceClass(persist = false, fifo = false, replicate = false)
public class FXSpot {
private String fxName;
private double modified;
private float value;
@SpaceId(autoGenerate = false)
public String getFxName() {
return fxName;
}
public void setFxName(String _fxName) {
fxName = _fxName;
}
@SpaceProperty(nullValue = "0")
public double getModified() {
return modified;
}
public void setModified(double _modified) {
modified = _modified;
}
@SpaceProperty(nullValue = "0")
public float getValue() {
return value;
}
public void setValue(float _value) {
value = _value;
}
}
The counterpart PONO (I have omitted the COM methods):
namespace com.mycompany.trading.fx
{
[ClassInterface(ClassInterfaceType.AutoDual), ComVisible(true)]
public class FXSpot
{
private string _fxName;
private double _modified;
private float _value;
public FXSpot()
{
_fxName = null;
_modified = 0;
_value = 0;
}
[SpaceID(AutoGenerate = false)]
[SpaceProperty(AliasName = "fxName", NullValue = "")]
public string FXName
{
get { return _fxName; }
set { _fxName = value; }
}
[SpaceProperty(AliasName = "modified", NullValue = 0)]
public double Modified
{
get { return _modified; }
set { _modified = value; }
}
[SpaceProperty(AliasName = "value", NullValue = 0)]
public float Value
{
get { return _value; }
set { _value = value; }
}
}
}
Java feeder – After looking up the space, and initializing Random helpers and currency names, it looks like:
while(true)
{
FXSpot spot = new FXSpot();
spot.setFxName(fxNames[ccyRand.nextInt(10)]);
double modified = (double)System.currentT imeMillis();
// convert to Excel date
modified = (modified + 7200000) / 86400000 + 25569;
spot.setModified(modified);
spot.setValue(valuesRandom.nextFloat());
System.out.println("Writing spot = " + spot);
spaceProxy.write(spot, null, Lease.FOREVER);
Thread.sleep(sleepTime);
}
Up until now, nothing new really… Now begins the interesting bit!
After omitting the initialization parts of the VBA code, what we have is the following:
Registration function:
Function RegisterNotifications(ByVal sRng As String)
If GigaSpace Is Nothing Then
Call Init
End If
Dim rng As range
rng = range(sRng)
Dim Template As FXObjects.FXSpot
Template = New FXObjects.FXSpot
Template.fxName = rng.Value
Dim modifiers As Integer
modifiers = NotificationModifiers.Update
Call GigaSpace.RegisterNotification(Template, "Notify", modifiers, sRng)
End Function
It is very easy to explain the code. If you have ever read the docs or used GigaSpaces’ notifications API, you should feel pretty comfortable here. Same rules apply… If you haven’t, a quick browse here will help understanding the API and terminology better.
You simply invoke GigaSpace.RegisterNotification method with a template to match, the name of your notify function, notify modifiers (take, write, update, all), and last argument which is not part of GigaSpaces notify API is called vbHint. It can hold any object the user wishes to receive back when the notify function is triggered for this specific registration (i.e. template match and operation match). In this example I have iterated through a list of currencies, and I pass the cell address of the specific currency to the registration so that when my Notify method is invoked, I can lookup the relevant cell easily.
My Notify function:
Function Notify(ByVal eventType As Long, ByVal pono As Object, ByVal vbHint As Object)
Dim sRng As String
sRng = vbHint
Dim rng As range
rng = range(sRng)
Dim spot As FXObjects.FXSpot
spot = pono
rng.Offset(0, 1).Value = spot.Value
rng.Offset(0, 2).Value = spot.Modified
End Function
Note the Notify signature. When registering to notifications, the notify function must have this signature in terms of the types it takes as arguments. The eventType represents the space operation which triggered the notification, and the pono is the object which matched the registration’s template and triggered the notify.
In this example, I take the values from the notification object, and update the relevant Excel cells (I use the vbHint for that).
The example includes a button to UnRegisterNotifications.
Public Sub UnReg()
If Not (GigaSpace Is Nothing) Then
Call GigaSpace.UnRegisterNotifications
End If
End Sub
The UnRegisterNotifications method removes all registrations for the invoking Excel from the space.
One more thing to note is the termination of the Excel process. As notifications require some daemon threads to run at the background, the Excel needs to invoke GigaSpace.Terminate function which cleans up these threads and frees some resources. Failing to invoke the method could result a hanging Excel process. As a best practice, you should catch the Excel workbook close event and call the terminate method.
Example (at the workbook level):
Private Sub Workbook_BeforeClose(ByVal Cancel As Boolean)
Call TerminateGigaSpace
End Sub
Which invokes the Terminate method:
Public Function TerminateGigaSpace()
If Not (GigaSpace Is Nothing) Then
Call GigaSpace.Terminate
End If
End Function
The example with inline comments and documentation is packed in the setup. After downloading and completing the installation process, the example Excel can be run from –> Programs –> VB Space API –> Examples –> FXSpot Notify. The example is located under \Examples\FXPrices. Follow the readMe.txt to run and change the example.
Enjoy!
-Guy
