// Set an appropriate CORS header if requested and if allowed
private void setCorsHeader(HttpServletRequest pReq, HttpServletResponse pResp) {
String origin = requestHandler.extractCorsOrigin(pReq.getHeader("Origin"));
if (origin != null) {
pResp.setHeader("Access-Control-Allow-Origin", origin);
pResp.setHeader("Access-Control-Allow-Credentials", "true");
}
}
private void sendResponse(HttpServletResponse pResp, String pContentType, String pJsonTxt)
throws IOException {
setContentType(pResp, pContentType);
pResp.setStatus(200);
setNoCacheHeaders(pResp);
PrintWriter writer = pResp.getWriter();
writer.write(pJsonTxt);
}
private void setContentType(HttpServletResponse pResp, String pContentType) {
boolean encodingDone = false;
try {
pResp.setCharacterEncoding("utf-8");
pResp.setContentType(pContentType);
encodingDone = true;
} catch (NoSuchMethodError error) {
/* Servlet 2.3 */
} catch (UnsupportedOperationException error) {
/* Equinox HTTP Service */
}
if (!encodingDone) {
// For a Servlet 2.3 container or an Equinox HTTP Service, set the charset by hand
pResp.setContentType(pContentType + "; charset=utf-8");
}
}
/**
* OPTION requests are treated as CORS preflight requests
*
* @param req the original request
* @param resp the response the answer are written to
*/
@Override
protected void doOptions(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
Map<String, String> responseHeaders =
requestHandler.handleCorsPreflightRequest(
req.getHeader("Origin"), req.getHeader("Access-Control-Request-Headers"));
for (Map.Entry<String, String> entry : responseHeaders.entrySet()) {
resp.setHeader(entry.getKey(), entry.getValue());
}
}
private void setNoCacheHeaders(HttpServletResponse pResp) {
pResp.setHeader("Cache-Control", "no-cache");
pResp.setHeader("Pragma", "no-cache");
// Check for a date header and set it accordingly to the recommendations of
// RFC-2616 (http://tools.ietf.org/html/rfc2616#section-14.21)
//
// "To mark a response as "already expired," an origin server sends an
// Expires date that is equal to the Date header value. (See the rules
// for expiration calculations in section 13.2.4.)"
//
// See also #71
long now = System.currentTimeMillis();
pResp.setDateHeader("Date", now);
// 1h in the past since it seems, that some servlet set the date header on their
// own so that it cannot be guaranteed that these headers are really equals.
// It happened on Tomcat that Date: was finally set *before* Expires: in the final
// answers some times which seems to be an implementation peculiarity from Tomcat
pResp.setDateHeader("Expires", now - 3600000);
}