Juicer is a nice tool to merge and minify several CSS files into just one file. Kudos to the guy that created it!
That said, I’ve been bitten several times by it. Here are some of the troubles I experienced and what I did to get things to work for me.
Juicer: embedding images in CSS
Juicer wants to know the –-document-root when embedding images with --force-image-embed or --embed-images data_uri.
Note that I’m talking about image inclusion in a css using relative URLs, I have not checked this for absolute urls because I don’t care: I never use then.
For things to work, the --document-root must be the directory of the css file you are processing.
Again, a clarification is in order: I always process just one css file each time with Juicer, because I make a point of creating a single css file that @imports all css files I want to consolidate. The net effect is that I’m processing several files, but specifying just one in the command line.
I’m making this clear so that you know I just haven’t tested Juicer behavior with --document-root and multiple css files in the command line. Better safe than sorry!
If you notice I’m being defensive, it is because I am. Juicer is great, but I’ve found its ways are not obvious to me and made many assumptions that did not hold.
Fixing relative CSS urls with ant
I run juicer from my project ant tasks, and that can be problematic because there are ant ways and there are Juicer ways, and they collide from time to time.
As point in case, I have to perform text substitution on the generated css file so that relative urls are right: this is due to the fact that Juicer seems to be intended to be run from the webapp root directory if you want correct relative urls in your css.
*But* I have not managed to run the ant task in the webapp root directory. I tried the dir attribute in the exec task, that seemed to be the cure, but that didn’t do what I needed.
Yes, I can bypass ant and run things from the command line. But then I will have ant’s way, the command line way, and will need to duplicate configuration information for ant and batch files (quick, where is the YUI compressor jar in your system/project?). And I hate breaking the DRY (Don’t Repeat Yourself) rule.
Workaround: replace ../WebContent/ with ../, WebContent being the subdirectory relative to my ant build.xml file. This is way simple in ant:
<replace
file="${juicer-friendly-output-dir}/${ant.project.name}-all.css"
token="url(../../WebContent/" value="url(../"/>
Juicer is written in Ruby, and Ruby has its ways
Ruby seems not to like ‘:’ or ‘\’ in file names -or Juicer uses that in a bizarre way.
Ok, I know almost nil about Ruby, but I had some bizarre problems with file names. In some cases, the error message I’ve got helped me clearly diagnose the problem.
In other cases, I had no error message, and it took a *lot* of time to identify the problem.
The workaround is avoiding ‘:’ or ‘\’ in file names passed directly or indirectly to Juicer.
Note that this can happen inadvertently. For example, if you execute an ant task in Windows, ant’s ${basedir} can end up being c:\x\y\z.
Workaround: convert all directory and file names to Unix style, which Windows handles correctly, like this:
<pathconvert property="juicer-friendly-input-dir" targetos="unix">
<path location="${basedir}/WebContent/css"/>
</pathconvert>
Juicer does not generate a non-minified css: but you can trick it into it
Juicer provides two nices features for CSS: consolidates several css files into one, and minifies the resulting file.
I would love to have a single production time css that is minified, and another one that is not, to help users of my js libraries with customizing the css. But Juicer does not provide a way to generate a non-minified version.
Workaround: specify a fake inexistent .jar file with the --path INEXISTENT_MINIFIER_JAR_TO_GET_NON_MINIFIED_CSS argument. Juicer will generate the consolidated css and will fail with a Unable to access jarfile error…but the consolidated css file with be there.
Yes, ugly, but very useful. I hope they had added a none option to the --minifyer argument that would have the same effect without the rror message, but they did not
Software Development "Built to Last" 
Best try a solution a little more “javera”, like wro4j (https://code.google.com/p/wro4j/) or Khawr (http://jawr.java.net/). I like especially wro4j and can also be used from the command line (https://code.google.com/p/wro4j/wiki/wro4jRunner). Also has standard support for relative paths, minify css, js minify and is also capable of flattening the @import that apparently are not very well seen lately (https://developers.google.com/speed/docs/best -practices/rtt # AvoidCssImport).
Yours trully,
Colomain.
Hi! How are you doing?
I’m using other means to do some of those things:
BTW, juicer can load the images in the CSS itself, and that was another killer feature I wanted. Do you know if wro4j supports this? Would like to try wro4j if it does, as it is likely more polished, better maintained and more familiar to me.
Do you know of some good sprite generator that will spit the result back into the CSS? That last feature is key, I don’t want to go around touching css files by hand, want everything to be automatically generated.
Do you have any suggestion about this?
Will take a look at wro4j to see whether is can turn into the only tool to use!
Hi, I’m doing well, thank you 🙂
For all your needs about css and js I think wro4j will do the trick… just look at all preprocessors and postprocessors they have implemented (http://code.google.com/p/wro4j/wiki/AvailableProcessors)
For images I don’t know what can else you cantry, but keep us informed, ok?
I’m currently figuring out howto make wro4j work well with some LESS css files I want to include… manly because I want to try Twitter Bootstrap framework for look&feel which make intensive use of LESS…
C.
Will take a look at wro4j at some time. Want to solve the sprite generation thing first, to have the whole optimization stack up and running, it is the last piece missing :).