/**
* Create a new CTWorkbook with all values set to default
*/
private void onWorkbookCreate() {
workbook = CTWorkbook.Factory.newInstance();
CTBookViews bvs = workbook.addNewBookViews();
CTBookView bv = bvs.addNewWorkbookView();
bv.setActiveTab(0);
workbook.addNewSheets();
sharedStringSource = (SharedStringsTable)createRelationship(XSSFRelation.SHARED_STRINGS, XSSFFactory.getInstance());
stylesSource = (StylesTable)createRelationship(XSSFRelation.STYLES, XSSFFactory.getInstance());