The enrolled fingerprint data can be found in Enroller.Template. Then use MemoryStream to to save and serialize the said fingerprint data. then pass the memorystream to your byte[] in order to upload it to your longblob column in your database.
Here's My example code in c# format:
byte[] byted;
private void featureS()
{
this.Invoke(new Function(delegate ()
{
MemoryStream fingerprintData = new MemoryStream();
Enroller.Template.Serialize(fingerprintData);
byted = fingerprintData.ToArray();
}));
}
I hope this gives you an idea. But before you save the fingerprint template, you must first verify if it already exist in the database.