我有一个 Java Servlet 后端,其数据存储区连接到我的应用程序;我正在尝试使用 Android Studio LoginActivity 模板实现登录系统,使用用户的电子邮件和密码(不是处理 Google 帐户登录的 PlusBaseActivity),但我不知道如何从这里开始:
你怎么能说用户已登录?以及如何才能如此持久地使用我的数据存储?我在这里读过:如何在 AppEngine Java 上使用 UserService 登录用户,我只需要调用方法resp.sendRedirect(userService.createLoginURL(req.getRequestURI()))
,我已经这样做了:
@Override
public void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException {
int size = checkDatastore(); // 0 if empty, > 0 if not empty
if(size==0){
populateDatastore();
}
String asyncMessage = req.getParameter("order");
if(asyncMessage.equals("login")){
mail = req.getParameter("email");
psw = req.getParameter("password");
UserService userService = UserServiceFactory.getUserService();
User user = userService.getCurrentUser();
String message="";
resp.setContentType("text/plain");
PrintWriter out = resp.getWriter();
if(user == null) {
//Sends a temporary redirect response to the client using the
// specified redirect location URL and clears the buffer.
String uri = userService.createLoginURL(req.getRequestURI());
resp.sendRedirect(uri);
User user1 = userService.getCurrentUser();
message="No one is logged in!\n" + "Sent from App Engine at " + new Date();
out.println(message);
out.flush();
}if(user !=null) {
// login(user);
message = "Hello, " + user.getEmail() +
", "+user.getNickname()+"!" + "\nSent from App Engine at "+ new Date();
out.println(message);
out.flush();
}
}
}
但该sendRedirect()
方法只给了我一个 URI。做什么的?
此外,User user = userService.getCurrentUser()
总是返回null
。怎么来的?