Raible Designs

Handling Time Consuming Requests

Domininic says, "I am try to find a good way to have an intermediate page load up while my Struts Action performs a large database query and then XSLT transformation." Ask and ye shall receive. I received the following e-mail from Alec Missine a while back. The attachment has a method of implementing a TCR. Let me know how it works as I haven't tried it myself.

----- Original Message -----
From: Alec Missine
To: [email protected]
Sent: Monday, January 07, 2002 3:59 PM
Subject: processing time consuming requests (was: wait page primer)


There's been some interest to the message I posted last month on the subject. The war file was too big though, so I compressed the stuff as much as I could. I also added some javadoc and UML diagrams.

The attached Struts-based application prototypes the wait page support for a time-consuming request (TCR). When a TCR (e.g., a database search) starts, the appropriate wait page is being sent to the browser after the request's ETC (Estimated Time to Complete) expires.

In the meantime, the corresponding action (the database search) is being started in the background thread on the server. If the default ETC is used (ad infinitum) or the action completes before the request's ETC expires, there is no wait page at all - the browser gets the result page right away, while the background thread is still busy closing the resources.

The wait page has javascript that polls the server to update the wait page with the TCR's progress. When the TCR completes, the wait page is being replaced with the appropriate result page.

This implementation has been tested on Apache Tomcat 4.0 with an Oracle 8.1.6 database as a data source. Presently, the application provides read-only access to all database tables for all database schemas through extensive use of the java.sql.DatabaseMetaData object. The next release will support insert/update/delete functionality.

Alec

Attachments: tcr.zip (114 KB)

Hope this helps!

Make your Flash HTML Standards Compliant

I initially found that the latest issue of A List Apart was published via web-graphics.com and then got this tidbit from Zeldman:

In Issue 154 of A List Apart, for people who make websites: “Flash Satay” by Drew McLellan. "This site uses Flash. This site validates as XHTML. They said it couldn’t be done. Now it can be. Have your Flash and standards, too." Please note, the ALA server may be slower than normal due to heavy traffic.

The technique involves using the following code:

<object type="application/x-shockwave-flash" data="c.swf?path=movie.swf" 
	width="400" height="300">
	<param name="movie" value="c.swf?path=movie.swf" />
	<img src="noflash.gif" width="200" height="100" alt="" />
</object>

Where c.swf is a container movie to workaround the fact that IE/Windows doesn’t stream the movie with this code.

Drew McLellan is the author of Dreamweaver MX Web Development and a member of The Web Standards Project’s Dreamweaver Task Force. You can follow the progress of this technique on his site.

WebGraphics also has an interesting post with a list of reasons why ease of use doesn't happen on engineering projects - uiweb.com