XMLRepo repo = XMLRepo.instance(pageContext); String uid = request.getParameter("uid"); String pid = request.getParameter("pid"); boolean ismgr = !"false".equals(request.getParameter("ismgr")); if ((uid != null) && (pid != null)) { Project project = (Project)repo.get(new Project(pid), false); User user = (User)repo.get(new User(uid), false); if (project != null && user != null) { if (ismgr && !project.isManager(user)) { project.addManager(user); repo.save(project); out.print("success"); return; } else if (!ismgr && project.isManager(user)) { project.removeManager(user); repo.save(project); out.print("success"); return; } } } failed