IRequestCycle obCycle = (IRequestCycle)event.getRequestCycle();
obCycle.getAbsoluteURL("/app?page=Login&service=page");
In Tapestry5 we can use the below code to get the absolute url.
@Inject
PageRenderLinkSource linkSource;
Link link = linkSource.createPageRenderLinkWithContext(
"DepartmentMasterPG",
5);
String s = link.toAbsoluteURI();