我有一个名为 LoginPage 的 java servlet，它是用户将登录信息输入表单的可视化界面，还有另一个名为 Login 的 servlet，它是一个临时页面，仅在重定向到另一个 servlet 之前进行检查、查询数据库以确认它确实是有效的登录。
//LoginPage
try (PrintWriter out = response.getWriter()) {
out.println("<!DOCTYPE html>");
out.println("<html>");
out.println("<head>");
out.println("<title>Login</title>");
out.println("</head>");
out.println("<body>");
out.println("<h1>Activities Week Login</h1></br>");
out.println("<form action=\"login\" method=\"post\">"
+ "Email:</br>"
+ "<input type='text' name='Email'></br>"
+"Password:</br>"
+ "<input type='password' name='Password'></br></br>"
+ "<input type='submit' value='Submit'></form>");
out.println("</br></br></br>");
out.println("Dont have an account yet? <a href=\'createaccountpage\'>Create one.</a></br></br>");
out.println("Forgotten your password? <a href=\'forgottenpasswordpage\'>Reset it.</a>");
out.println("</body>");
out.println("</html>");
}
//Login
SQLConnection sqlconnection = new SQLConnection();
String Email = (String)request.getParameter("Email");
String Password = (String)request.getParameter("Password");
if(sqlconnection.checkValidLogin(Email, Password) == false)//If the login details are incorrect:
{
PrintWriter out = response.getWriter();
out.println("<meta http-equiv='refresh' content='3;URL='>");//redirects after 3 seconds
out.println("<p style='color:red;'>Login unsuccessful! Please check your details and try again.</p>");
response.sendRedirect("");
}
else//If the login details are correct:
{
User currentUser = sqlconnection.getCurrentUser(Email);
HttpSession session = request.getSession();
session.setAttribute("Email", Email);
if(sqlconnection.isUserTeacher(Email)==true)//If the user is a teacher
{
Teacher currentTeacher = new Teacher();
currentTeacher.setUser(currentUser);
session.setAttribute("currentTeacher", currentTeacher);
PrintWriter out = response.getWriter();
out.println("<meta http-equiv='refresh' content='3;URL=studenthomepage'>");//redirects after 3 seconds
out.println("<p style='color:green;'>Login successful!</p>");
response.sendRedirect("studenthome");
}
else{
Student currentStudent;
currentStudent = sqlconnection.getCurrentStudent(Email, currentUser);
session.setAttribute("currentStudent", currentStudent);
PrintWriter out = response.getWriter();
out.println("<meta http-equiv='refresh' content='3;URL=studenthomepage'>");//redirects after 3 seconds
out.println("<p style='color:green;'>Login successful!</p>");
response.sendRedirect("studenthome");
}
}
如果提供的登录信息不正确，如何显示重定向回登录页面时保留的错误消息？
我已经看到并尝试了一些其他方法(没有帮助)，例如登录 servlet 中已有的方法:
out.println("<meta http-equiv='refresh' content='3;URL=studenthomepage'>");//redirects after 3 seconds
out.println("<p style='color:green;'>Login successful!</p>");
这个方法不是一个好的解决方案吗(或者我只是做错了)，如果是的话我应该使用什么？
最佳答案
您可以使用一些消息来设置属性，如下所示:
String msg= "Sorry !! You have an error";
request.getSession().setAttribute("msg", msg);//setting attribute
// forwards message to your page
request.getRequestDispatcher("yourloginpage").forward(request,response);
现在，在您的登录页面上在表单顶部写下如下内容:
HttpSession session = request.getSession();//getting session
String msg;
//checking if msg is not null
if(session.getAttribute("msg")!=null){
msg= (String)session.getAttribute("msg");
out.println("<p style='color:green;'> "+msg+"</p>"); //printing message
}
希望这对您有帮助!
关于java - 如何显示重定向回不同 servlet 时保留的错误消息？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/55747696/