New session after download - angular js - internal rest call - angularjs

Question

I have an ng-click implementation that does a $http.post() call to the server which returns a file content. so, a file download happens on the browser. below is the code snippet:
$scope.downloadFile = function(mediaObj) {
var downloadReq = {
"cid": $cId,
"pid":$pId,
"mid":$mId
};
$http.post(<server url>, downloadReq)
.then(function(response) {
var downloadUrl = URL.createObjectURL(new Blob([response.data]));
var a = document.createElement('a');
a.href = downloadUrl;
a.target = '_blank';
a.download = response.headers('Content-Disposition').split(';')[1].trim().split('=')[1];
document.body.appendChild(a);
a.click();
a.remove();
}, function(response) {
//unable to download
$scope.downloadErr = true;
});
}
server side code snippet is like this:
public void handleDownloadRequest(String json, HttpServletRequest request, HttpServletResponse httpServletResponse) {
....
// make rest call to another microservice to get file content
IOUtils.copyLarge(new ByteArrayInputStream((byte[])response.getBody()), httpServletResponse.getOutputStream());
// copy all headers from rest call response to httpServletResponse
httpServletResponse.flushBuffer();
}
after this, the next call to server (it need not be download itself, any other server call) is getting a brand new session. the old session has been destroyed.
because of this, server side client session state is lost and working on the client is messed up.
can anyone please help me with understanding why a new session is getting created after the download operation? how i can avoid this? why is the old session getting destroyed?
Thanks in advance.

Answer 1

I am answering my own question. Maybe it will save someone's time. As part of the handleDownloadRequest() method, i was making a rest call to another microservice to get the file data. the httpresponse of that rest call had a new session id that was also getting copied into the httpServletResponse of the handleDownloadRequest() method.
this was getting propagated to the client and in turn the client session state was lost.
SOLUTION: i removed the session cookie header from the response while copying over the headers.
Take care of the http response while making internal rest calls...