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.
A response header is an HTTP header that can be used in an HTTP response and that doesn't relate to the content of the message. Response headers, like Age , Location or Server are used to give a more detailed context of the response.
An HTTP header is a field of an HTTP request or response that passes additional context and metadata about the request or response. For example, a request message can use headers to indicate it's preferred media formats, while a response can use header to indicate the media format of the returned body.
Setting Response Headers from Servlets The most general way to specify headers is to use the setHeader method of HttpServletResponse. This method takes two strings: the header name and the header value. As with setting status codes, you must specify headers before returning the actual document.
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");
}
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");
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