System Template

sendHTTPheaders()

Force all HTTP headers to be sent to the browser now.

Syntax

void = rb.page.sendHTTPheaders()

Parameters

The 'sendHTTPheaders' method takes no parameters

Results

The 'sendHTTPheaders' method returns no useful information.

Remarks

The normal behaviour of the Presentation Engine is to process a page request completely and the send the generated output to the browser. This means the browser will not send any output to the client until the entire page has completed. In general this behaviour is fine. However most browsers will eventually timeout a request if they do not receive at least the headers within a certain, browser specific, time. As long as the headers are sent the browser will wait patiently for the rest of the content.

For virtually all pages the behaviour of the presentation engine is fine - the browser timeouts are sufficiently long that they will not occur for the generation of any reasonable web page request.

There are a few situations however where a page can legitimately take longer that the browser timout. Most of these pages concern site administration - a good example being a page that uploads a catalogue file to populate the web-site with product information. In this case the processing of the data file can consume significant periods of time. In this situation the Pattern Page must force the Presentation Engine to send headers early to prevent the browser timeout occurring.

This method forces the Presentation Engine to immediately send all headers to the browser.

Note - this method only works once - the first time it is called the system sends all the accumulated header information to that point. Subsequent calls are ignored. Causing operations that affect the headers after calling this method are effectively ignored - the headers have already been dispatched!

In practice this means than any operations on the rb.page.cookie object or calls to rb.page.writeheader() must take place before calling this method.

Example

The following example formats an cookie to be sent to the browser and then forces the data to be sent to the browser before starting a lengthy operation.

<rb:script>
   var data = new Object;
   data.name = "Redbourne";
   data.phone = "0870 166440";

   rb.page.cookie.write("AppData", data);
   rb.page.sendHTTPheaders();

   // Now do some processing that takes a long time.
   ....
</rb:script>