Setting the notifyURL for the PayPal IPN

In the previous post we saw how to implement a PayPal IPN listener. This is a quick post to show you how to set this listener using PayPal Website Payments Standard.

First you create your "Buy Now" (or "Add to Cart", "Subscribe"...) button. You can do this at https://www.paypal.com/cgi-bin/webscr?cmd=_wp-standard-overview-outside. This wizard creates a form with a couple of hidden parameters. It doesn't set the notify url however, which is the url PayPal IPN needs to call to notify you the user made a purchase. You can add this url to the form as follows:

<input type="hidden" name="notify_url" value="<h:outputText value="#{paypalBean.notifyURL}"/>" />

This sample uses JSF to create the URL, but you can use any tag here (or use a hardcoded URL).

Here is the code that generates the URL:

public String getNotifyURL() {
HttpServletResponse response = (HttpServletResponse) FacesContext.getCurrentInstance().getExternalContext().getResponse();
String nUrl = getPath("PaypalListenerServlet");
return response.encodeURL(nUrl);
}

public final static String getPath(String path) {
HttpServletRequest request = (HttpServletRequest) FacesContext.getCurrentInstance().getExternalContext().getRequest();
StringBuffer url = new StringBuffer();
String s = request.getProtocol();
url.append(s.substring(0, s.indexOf('/')).toLowerCase());
url.append("://");
url.append(request.getServerName());
url.append(":");
url.append(request.getServerPort());
url.append(request.getContextPath());
if (path.charAt(0) != '/') {
url.append("/");
}
url.append(path);
return url.toString();
}