HttpSession session=request.getSession(false); ruturning null

问题

my code is

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub

    HttpSession session=request.getSession(false);

    if(session==null){

        response.sendRedirect(request.getContextPath());
    }else{

        doPost(request,response);
    }

}

the url pattern for this servlet is /loginServlet. i wrote this code so that if user is logged in and makes a get request by hitting enter on the url then the request must be forwarded to doPost() or else if the user is not logged in then he get to the login page

but the problem is that its always returning to the login page that means request.getSession(false) always returning null

how can i solve this problem

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    String name=request.getParameter("name");
    String commun=request.getParameter("commun");
    String password=request.getParameter("password");
      Connection conn = null;
      Statement  statement = null;


    try{
    Context initContext = new InitialContext();
    Context envContext = (Context) initContext.lookup("java:comp/env");
    DataSource ds = (DataSource) envContext.lookup("jdbc/community");
     conn = ds.getConnection();

      statement = conn.createStatement();
      String sql = "select memberragas from windowragas where memberragas='"+name+"' and liquid_key='"+commun+"' and chabhiragas='"+password+"'";
      ResultSet rs =statement.executeQuery(sql);
     if(rs.next()){
         System.out.println("welcome "+name+"");
         HttpSession session=request.getSession();
         session.setAttribute("name", name);
         session.setAttribute("commun", commun);
         RequestDispatcher rd = request.getRequestDispatcher("/homey");
         rd.forward(request, response);


     }else{
         System.out.println("either ur username or password or community was wrong");
         response.sendRedirect(request.getContextPath());
     }
    }
 catch (NamingException ex) {
    System.err.println(ex);
} catch (SQLException ex) {
    System.err.println(ex);
}finally {

    try {
       if (statement != null) statement.close();
       if (conn != null) conn.close();  // return to pool
    } catch (SQLException ex) {
        ex.printStackTrace();
    }
 }
}

in the doPost() i m creating the session for the first time

回答1:

I believe the issue is that when you call doPost() directly from your doGet() method, the request parameters name, commun and password are not available. Hence, the authenticating SQL query fails and your else block executes.

 } else {
     System.out.println("either ur username or password or community was wrong");
     response.sendRedirect(request.getContextPath());
 }

This is effectively the same as your doGet()'s if block and hence gives an impression that your session is null.

if (session == null) {
    response.sendRedirect(request.getContextPath());
}

So to fix the issue, if the session exists, redirect the user immediately instead of trying to execute doPost() to authenticate them again. The presence of name attribute can further assure that the user has been authenticated before.

if (session != null && session.getAttribute("name") != null) {
    RequestDispatcher rd = request.getRequestDispatcher("/homey");
    rd.forward(request, response);
} else {
    response.sendRedirect(request.getContextPath());
}

来源：https://stackoverflow.com/questions/32046303/httpsession-session-request-getsessionfalse-ruturning-null

标签

session

servlets