How to set a header in an HTTP response

Question

I ve a servlet A where I m setting a header in the HTTP response   public void doPost HttpServletRequest request  HttpServletResponse response          throws ServletException  IOException        String userName request getParameter  userName        String newUrl    http   somehost port ServletB        response addHeader  REMOTE USER   userName        response sendRedirect newUrl       Now in a servlet B  I m trying to get the header value that was set in the servlet A   public void doPost HttpServletRequest request  HttpServletResponse response          throws ServletException  IOException        String userid   request getHeader  REMOTE USER         But here the value of userid is coming as null  Please let me know what I m missing here

User · Answer

Header fields are not copied to subsequent requests  You should use either cookie for this  addCookie method  or store  REMOTE USER  in session  which you can obtain with getSession method

User · Answer

In my Controller  I merely added an HttpServletResponse parameter and manually added the headers  no filter or intercept required and it works fine   httpServletResponse setHeader  Access-Control-Allow-Origin         httpServletResponse setHeader  Access-Control-Allow-Methods    GET  OPTIONS    httpServletResponse setHeader  Access-Control-Allow-Headers   Origin  X-Requested-With  Content-Type  Accept  X-Auth-Token  X-Csrf-Token  WWW-Authenticate  Authorization    httpServletResponse setHeader  Access-Control-Allow-Credentials    false    httpServletResponse setHeader  Access-Control-Max-Age    3600

User · Answer

First of all you have to understand the nature of   response sendRedirect newUrl     It is giving the client  browser  302 http code response with an URL  The browser then makes a separate GET request on that URL  And that request has no knowledge of headers in the first one    So sendRedirect won t work if you need to pass a header from Servlet A to Servlet B   If you want this code to work - use RequestDispatcher in Servlet A  instead of sendRedirect   Also  it is always better to use relative path   public void doPost HttpServletRequest request  HttpServletResponse response  throws ServletException  IOException       String userName request getParameter  userName        String newUrl    ServletB       response addHeader  REMOTE USER   userName       RequestDispatcher view   request getRequestDispatcher newUrl       view forward request  response                                 public void doPost HttpServletRequest request  HttpServletResponse response        String sss   response getHeader  REMOTE USER

[java] How to set a header in an HTTP response?

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