Hints and Kinks

The first issue was how to build the smallest possible byte array that represents a 1×1 GIF. Using ImageMagick piped to base64 made it easy to embed into java code:

convert -size 1x1 xc:transparent gif:- | base64

At servlet load time, un-base64 the gif back into the byte array:

import org.apache.commons.codec.binary.Base64;
...
private static final String PIXEL_B64 = "R0lGODlhAQABAPAAAAAAAAAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw==";
private static final byte[] PIXEL_BYTES = Base64.decode(PIXEL_B64.getBytes());

in your handle method, then write those bytes to the output stream:

httpServletResponse.setContentType("image/gif");
httpServletResponse.getOutputStream().write(PIXEL_BYTES);

java, web

How to increase maven heapspace in hudson builds

Nov 23rd

Posted by matthew in Technical HOWTOs

If your maven-built project fails in hudson (especially when you’re using the assembly plugin) and it isn’t a compile or test failure, check the console output. If it says “java.lang.OutOfMemoryError: Java heap space”, you need to configure your hudson job to add heap space to the maven process.

Navigate to your hudson job,
click Configure,
scroll down to the Build section, and
click the Advanced button.
Enter this into MAVEN_OPTS: -Xmx512m -XX:MaxPermSize=128m

hudson, java, maven, maven2

OpenDNS updater for linux/ubuntu

Nov 15th

Posted by matthew in Technical HOWTOs

The OpenDNS service is great — it provides anti-phishing and the ability to filter out some of the less desirable detritus from the internets.

OpenDNS needs to be periodically notified about what your IP address is, and I don’t have a windows or macintosh box that’s always on. I do have an ubuntu box, though, but there weren’t any instructions on OpenDNS’ site to do this properly.

cron, linux, opendns, ubuntu

How to Convert Your Book’s Images to Kindle

Nov 7th

Posted by matthew in Technical HOWTOs

Taking your painstakingly typeset book and shoving it through the kindle “conversion” meatgrinder was an exercise in wincing. Most of the images were corrupted, there was whitespace sprinkled randomly throughout the copy, and it was a general mess.

Kindle supports direct upload of an html version of your book, but there’s a lot of finessing you need to do before it all goes smoothly. One of the tasks you’ll need to do is convert your book’s images to greyscale, and reduce their size to something Kindle-friendly. There are free tools to help you do this if you aren’t afraid of the terminal.

imagemagick, kindle, macports, Pages, sh, shell hackery

Simple Image Slideshow with jQuery and PHP

Sep 1st

Posted by matthew in Photography

I really liked Jon Raasch’s jquery-powered slideshow, but integrating it into a page requires a bunch of steps:

Add the jQuery library
Add the slideshow javascript function
Add the CSS with opacity and z-layer set properly
Upload the images for the slideshow someplace
Enumerate the images’ URLs that you want to cycle through

Adding images is tedious (you have to upload AND update the image list), and there’s no clean support for multiple slideshows per page. I wanted a process that made integration into other pages trivial.

I decided that an IFRAME to host the slideshow would keep jQuery and the slideshow CSS partitioned away from the rest of the embedding page, and would let adding slideshows to new pages have an easy-to-follow recipe, no matter what was already going on in the existing page. The IFRAME needed the template HTML, and if I used PHP, I could generate the image list for the slideshow automatically from the images that live in the same directory as the PHP script.

javascript, jquery, php

Automatic disposable email addresses for Google Apps

Aug 29th

Posted by matthew in Technical HOWTOs

Plus Suffixing

There’s a pretty nifty feature with gmail that most people don’t know about. I’ve seen people reference it as the “plus hack” or “plus suffixing”. If you have username@gmail.com, you can add a “+” followed by any letters and numbers, and it will still be delivered to username@gmail.com.

I’ve been using this for corporate email forms — if facebook wants an email, they get matthew+facebook, for example. I can then add a precise filter on that “To:” address and delete all email from that company if it “goes evil.”

There’s a glitch in plus suffixing, though — most web forms don’t realize that the plus sign is a totally valid email character, and will reject your plus-suffixed hack.

So what to do?

Well, if you’re using gmail, you’re out of luck. But if you’re using a google apps account for a custom domain (say, your company or family), and you are an administrator for that domain, you can enable “minus suffixing”!

email, google apps

Installing Trac on Ubuntu

Aug 27th

Posted by matthew in Technical HOWTOs

Here’s the condensed version, using the installation guide for help:

subversion, trac, ubuntu

Apache2, PHP, and MySQL on Mac OS X using MacPorts

Aug 24th

Posted by matthew in Technical HOWTOs

1. Install MacPorts

Follow the instructions here: http://www.macports.org/install.php.

2. Install apache2

sudo port install apache2

Note that the macports instructions suggest installing the launchctl script now, but we’ll do that after mysql and php are installed.

3. Install and configure MySQL

If you want 5.0.x, use mysql5-server. If you need 5.1.x, install mysql5-server-devel (at least as of August 2009).

sudo port install mysql5-server

As the macports instructions state,

In order to setup the database, you might want to run sudo -u mysql mysql_install_db5 if this is a new install.

It’s never a bad idea to set the root password, and as the document suggests, run:

/opt/local/lib/mysql5/bin/mysqladmin -u root password 'new-password'

You also want to install a database configuration file — there are a bunch of templates in /opt/local/share/mysql5/mysql/, but for development, my-small.cnf should suffice:

sudo cp /opt/local/share/mysql5/mysql/my-small.cnf /opt/local/etc/mysql5/my.cnf

Once the config is in place, spin up mysql:

sudo launchctl load -w /Library/LaunchDaemons/org.macports.mysql5.plist

Check that mysql is up and running by connecting with the mysql client:

mysql -h localhost -u root -p

4. Fix your PATH

Note that the mysql binaries in /opt/local/bin all have a “5″ suffix, but /opt/local/lib/mysql5/bin has “normal” named binaries, so you probably want that in your PATH too. The apachectl in /usr/bin will spin up the mac os x version of apache (that we’re avoiding), and that lives in /opt/local/apache2/bin. So in your .bashrc (or .profile or whatever):

export PATH=/opt/local/bin:/opt/local/sbin:/opt/local/lib/mysql5/bin:/opt/local/apache2/bin:$PATH

5. Install PHP5

sudo port install php5 +pear +apache2 +fastcgi +mysql5

Note that php5 has a lot of variants. If you think you want other goodness, run port variants php5 and cook up your own set of options.

Again, as the macports instructions state,

copy /opt/local/etc/php5/php.ini-development (if this is a development server) or /opt/local/etc/php5/php.ini-production (if this is a production server) to /opt/local/etc/php5/php.ini and then make changes.

6. Install the PHP-MySQL driver:

sudo port install php5-mysql +mysql5

7. Configure apache2

The mod_php.conf from the php5 package is put into a directory that the apache2 configuration doesn’t read by default — so you need to add this line to the end of /opt/local/apache2/conf/httpd.conf:

Include conf/extras-conf/*

Hopefully this will be considered a packaging bug, and will be fixed at some point.

8. Run apache2

sudo launchctl load -w /Library/LaunchDaemons/org.macports.apache2.plist

Note that the logs, by default, are in /opt/local/apache2/logs.

If you change the PHP or Apache configuration files, run

sudo /opt/local/apache2/bin/apachectl restart

and watch the logs for errors.

apache2, mac, mac os x, macports, mysql, php

How to pause crashplan on Mac OS X

Aug 17th

Posted by matthew in Technical HOWTOs