Paypal-IPN Simulator ends up in HTTP 404 error after successfully completion of the function - paypal-ipn

Question

have spent lot of hours trying to figure this out with Paypal Simulator, Sandbox but the result is same. My handler function(handleIpn) gets called and processed, with "Verified" "Complete" status but the IPN history as well as the simulator ends up in the HTTP 404 error. On IPN Simulator page the error is - "We're sorry, but there's an HTTP error. Please try again." My set up is Java-Spring MVC.
#RequestMapping(value = "/ipnHandler.html")
public void handleIpn (HttpServletRequest request) throws IpnException {
logger.info("inside ipn");
IpnInfo ipnInfo = new IpnInfo();
Enumeration reqParamNames = request.getParameterNames();
StringBuilder cmd1 = new StringBuilder();
String pName;
String pValue;
cmd1.append("cmd=_notify-validate");
while (reqParamNames.hasMoreElements()) {
pName = (String) reqParamNames.nextElement();
pValue = request.getParameter(pName);
try{
cmd1.append("&").append(pName).append("=").append(pValue);
}
catch(Exception e){
e.printStackTrace();
}
}
try
{
URL u = new URL("https://www.sandbox.paypal.com/cgi-bin/webscr");
HttpsURLConnection con = (HttpsURLConnection) u.openConnection();
con.setRequestMethod("POST");
con.setRequestProperty("Host", "www.sandbox.paypal.com/cgi-bin/webscr");
con.setRequestProperty("Content-length", String.valueOf(cmd1.length()));
con.setRequestProperty("Content-Type","application/x-www-form-urlencoded");
con.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0;Windows98;DigExt)");
con.setDoOutput(true);
con.setDoInput(true);
DataOutputStream output = new DataOutputStream(con.getOutputStream());
output.writeBytes(cmd1.toString());
output.flush();
output.close();
//4. Read response from Paypal
BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
String res = in.readLine();
in.close();
//5. Capture Paypal IPN information
ipnInfo.setLogTime(System.currentTimeMillis());
ipnInfo.setItemName(request.getParameter("item_name"));
ipnInfo.setItemNumber(request.getParameter("item_number"));
ipnInfo.setPaymentStatus(request.getParameter("payment_status"));
ipnInfo.setPaymentAmount(request.getParameter("mc_gross"));
ipnInfo.setPaymentCurrency(request.getParameter("mc_currency"));
ipnInfo.setTxnId(request.getParameter("txn_id"));
ipnInfo.setReceiverEmail(request.getParameter("receiver_email"));
ipnInfo.setPayerEmail(request.getParameter("payer_email"));
ipnInfo.setResponse(res);
// ipnInfo.setRequestParams(reqParamNames);
//6. Validate captured Paypal IPN Information
if (res.equals("VERIFIED")) {
//6.1. Check that paymentStatus=Completed
if(ipnInfo.getPaymentStatus() == null || !ipnInfo.getPaymentStatus().equalsIgnoreCase("COMPLETED"))
ipnInfo.setError("payment_status IS NOT COMPLETED {" + ipnInfo.getPaymentStatus() + "}");
//6.2. Check that txnId has not been previously processed
IpnInfo oldIpnInfo = this.getIpnInfoService().getIpnInfo(ipnInfo.getTxnId());
if(oldIpnInfo != null)
ipnInfo.setError("txn_id is already processed {old ipn_info " + oldIpnInfo);
//6.3. Check that receiverEmail matches with configured {#link IpnConfig#receiverEmail}
if(!ipnInfo.getReceiverEmail().equalsIgnoreCase(this.getIpnConfig().getReceiverEmail()))
ipnInfo.setError("receiver_email " + ipnInfo.getReceiverEmail()
+ " does not match with configured ipn email " + this.getIpnConfig().getReceiverEmail());
//6.4. Check that paymentAmount matches with configured {#link IpnConfig#paymentAmount}
if(Double.parseDouble(ipnInfo.getPaymentAmount()) != Double.parseDouble(this.getIpnConfig().getPaymentAmount()))
ipnInfo.setError("payment amount mc_gross " + ipnInfo.getPaymentAmount()
+ " does not match with configured ipn amount " + this.getIpnConfig().getPaymentAmount());
//6.5. Check that paymentCurrency matches with configured {#link IpnConfig#paymentCurrency}
if(!ipnInfo.getPaymentCurrency().equalsIgnoreCase(this.getIpnConfig().getPaymentCurrency()))
ipnInfo.setError("payment currency mc_currency " + ipnInfo.getPaymentCurrency()
+ " does not match with configured ipn currency " + this.getIpnConfig().getPaymentCurrency());
}
else
ipnInfo.setError("Inavlid response {" + res + "} expecting {VERIFIED}");
logger.info("ipnInfo = " + ipnInfo);
this.getIpnInfoService().log(ipnInfo);
//7. In case of any failed validation checks, throw {#link IpnException}
if(ipnInfo.getError() != null)
throw new IpnException(ipnInfo.getError());
}
catch(Exception e)
{
if(e instanceof IpnException)
throw (IpnException) e;
logger.log(Level.FATAL, e.toString(), e);
throw new IpnException(e.toString());
}
//8. If all is well, return {#link IpnInfo} to the caller for further business logic execution
paymentController.processSuccessfulPayment(ipnInfo);
}
Any help /pointers would greatly appreciate.
thanks.

Answer 1

Finally, got it working! Didn't realize that my issue of redirection in Spring MVC could have impact on Paypal - IPN status. May be my lack of good understanding of HTTP redirections! In above method instead of void return am now returning a jsp page, so "void" is changed to "String" with returning value the jsp file name.
Hope it does help someone!