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Devon Hillard Tech Blog

Java, ATG, Seam, and related Technologies

Eclipse, Subversion, and SSH_OPEN_ADMINISTRATIVELY_PROHIBITEDYesterday

If you use the Subclipse plugin to access subversion repositories from Eclipse using the ssh+svn protocol, you may see errors like this:

SSH_OPEN_ADMINISTRATIVELY_PROHIBITED

when you try to do too many things at once.

When I tried switching to JavaHL instead of SVNKit, I got different errors, so that was out.

Adding this line to my eclipse.ini file fixed it though:

-Dsvnkit.ssh2.persistent=false

It prevents the SVNKit adapter from issuing multiple sessions through a persistent SSH connection, which seems to trigger the error on some SSH servers at least.

Apache mod_deflate and mod_cache issuesNovember 18

The Problem: Using Apache mod_deflate and mod_disk_cache (or other mod_cache) together can create far too many cached files.

The Background: Apache is a web server with many different modules you can load in to enhance it. Two common ones are mod_deflate and mod_cache (or mod_disk_cache).

Mod_deflate compresses content that is sent to the webserver using gzip. It can take 100k of html, css, or javascript, and compress it down to ~10k, before transmitting it to the user's browser. The browser then uncompresses it, and displays the page. Most web servers (depending on how your site/application is structured anyway) are not CPU limited. Therefore, you can spend some extra CPU doing the compression, and get much faster content delivery times to your users, who are often bandwidth limited. Not only does this make pages load faster for your users, but it also allows request handling threads to complete sooner, letting your web server handle more requests.

Some web browsers are not able to handle gzipped content correctly, therefore it's important to add in some logic to only send gzipped content to browsers who can handle it. Also, there are different types of files which are already compressed and hence trying to gzip them is a waste of time and resources, such as images, video, etc...

A common configuration may look like this:

# Insert filter SetOutputFilter DEFLATE # Netscape 4.x has some problems... BrowserMatch ^Mozilla/4 gzip-only

Why I Won’t Deal With Trans-AmericanOctober 30

Generally I'd never post about a negative business interaction. We've all worked with bad recruiters, bad employers, bad contractors, and so on. I like to give people the benefit of the doubt, and I don't want to bad-mouth anyone.

That said, Trans-American has pushed my limits too far. These guys are some sort of ATG recruiting firm or something, I really don't know. They started calling me perhaps 6 weeks ago, asking if I was interested in a position. I told them very clearly, that I was on a contract which I was very happy with. That I would be at least through the end of the year. And they could call again in January. The same guy called again the next week. And twice every week since. I could not have been more clear, every single time. I was polite, but clear that I was not interested. And it was the same guy calling every time. I don't know how many ATG architects named Devon at my phone number he's dealing with, but the complete inability to respect my clear wishes, is amazing.

I will never do business with Trans-American, and I would recommend that everyone else avoid them as well.

10MinuteMail Performance ImprovementOctober 21

After having a clearly better approach to mail delivery pointed out to me by a friend yesterday, I pushed a new version of 10MinuteMail out last night. End users shouldn't notice anything different, but behind the scenes the mail acceptance and delivery is MUCH higher performing. There should be less incoming mail delays, slow pages, and less domain changing. Inactive e-mail addresses will return a bounce notice now, as they probably should have done from the start.

I apologize for the delivery issues yesterday, before I made the change, the amount of incoming junk was really slamming on the server. Hopefully that's a thing of the past now.

Preventing Multiple Submits On An ATG FormOctober 10

Often, you'll want to prevent impatient users from clicking a submit button multiple times, as you can end up with multiple actions taking place, or object state can get in a bad way leading to errors. For this example we'll assume you have a final Submit Order form that actually places the order, auth's the credit card, etc...

You can't simply disable the submit button onclick with ATG as typically the submit button is the input field that actually activates the handle method. I tried a bunch of things, before I was able to get something working, so I wanted to share that here.

First thing is to write some javascript that will handle all of the magic (this example uses jQuery):

  <SCRIPT language="JavaScript"> function submitform() { $('#commitOrderButton').attr("href","#"); document.myFormsName.submit(); } </SCRIPT>  

Second, you need to move the input that calls the correct handle method out of the submit button and into a hidden form field:

  <dsp:input bean="CommitOrderFormHandler.commitOrder" value="submit" type="hidden" />  

Thirdly you'll want to replace the submit input with a submit <a> which will call your javascript:

<a href="javascript:submitform()" id="commitOrde