How to pass data in HTTP Header while redirecting

问题:

is it possible to pass some data in HTTP Header, while redirecting a request from one server to another.

Here is my scenario, I have one generic filter, via which every request is passing. Now, based on some condition, I'm redirecting the request to some different server using the API objHttpServletResponse.sendRedirect(strURL).

But, the issue is, when I'm setting some data in response header like objHttpServletResponse.setHeader("Key", "Value"); That's not available in the redirected server.

So, my questions are,

1. Is there any way to pass some data in header while redirecting a request?

2. If not, what are the other possible ways to send some data while redirecting a request?

Please Note: few other ways, like

using URL parameters: objHttpServletResponse.sendRedirect(strURL+"?param="+ strParamValue);

or

using session: HttpSession session = httpRequest.getSession(); session.setAttribute("Key", "Value");

is not what I'm expecting.

回答1:

The headers you set are written to the response that gets sent to the client, along with a Location header and a status code. See Redirecting a request using servlets and the "setHeader" method not working

The client is then supposed to send an identical request to the URL you specified in the Location header. Identical to the request it sent to you.

You want the browser to send a header you specify along with the redirected request. Have you considered adding a (domain) Cookie header? Some googling leads me to believe that cookies set in a redirect response will get picked up by most browsers. See http://blog.dubbelboer.com/2012/11/25/302-cookie.html

回答2:

Please have a look at Apache HttpClient.

This example adds several parameters to the post request :

    String url = "https://selfsolve.apple.com/wcResults.do";

    HttpClient client = HttpClientBuilder.create().build();
    HttpPost post = new HttpPost(url);

    // add header
    post.setHeader("User-Agent", USER_AGENT);

    List<NameValuePair> urlParameters = new ArrayList<NameValuePair>();
    urlParameters.add(new BasicNameValuePair("sn", "C02G8416DRJM"));
    urlParameters.add(new BasicNameValuePair("cn", ""));
    urlParameters.add(new BasicNameValuePair("locale", ""));
    urlParameters.add(new BasicNameValuePair("caller", ""));
    urlParameters.add(new BasicNameValuePair("num", "12345"));

    post.setEntity(new UrlEncodedFormEntity(urlParameters));

    HttpResponse response = client.execute(post);
    System.out.println("Response Code : " 
                + response.getStatusLine().getStatusCode());

回答3:

The problem is that the redirect() method of the response initiates a new request altogether, thereby loosing the attributes that were set before redirecting. Luckily there is a fluent way of solving the problem still.

response.setHeader("Key", "Value");
request.getRequestDispatcher("redirecturl").forward(request, response);

Then in your destination you can do

response.getHeaders("key")

回答4:

You can use JS redirect, i.e. instead of calling sendRedirect return HTML page with embedded javascript that will do redirect setting headers you need.

However, using GET parameters is really the best solution. If you have concerns about users altering parameters manually - use MAC code to protect parameters.See Message authentication code

In simplest form, ?p1=1&p2=2&mac={mac value}, where {mac value} = md5('MY_SECRET_KEY' + 'p1=1&p2=2'). Receiving side can recalculate MAC and compare it with provided one. Since external users can not know 'MY_SECRET_KEY', they will not be able to make valid MAC.

回答5:

Have you checked the HTTP request/response from/to server? You can use a number of plugins on chrome or firefox to check that. You would be able to see if value is being passed from your server to another server or not
Also retrieve the header using httpResponse.getHeader("Key"); not using request.getHeader("key"). One of my colleague was facing same issue some days back, he was using request to fetch header values