Jawr is an Open Source library which offers two
complementary uses for java and Facelets web applications in which
_javascript_ is heavily used:
- First, it's a productivity tool, since it allows to develop
_javascript_ components in separate files, each representing a module, as
opposed to having all the code in one or two files for performance
reasons. Working with separate files makes development, maintenance and
version control a lot easier.
- On the other hand, Jawr is a performance tool which will
perceivably improve page loading times. When in production mode, all
the modules which were split in separate files are bundled together
(into one or several files, as per configuration), then minified, then
compressed and sent to the client using aggressive caching headers.
This reduces the number of HTTP requests required to load a full page
and also the size in kilobytes that a user must download. Jawr
implements many of the good practices defined in this very interesting
article which I recommend everyone to read: serving _javascript_ fast.
Jawr is configured by adding a servlet to our application and creating
a simple .properties file to configure the way components are to be
bundled. CSS files can also benefit from bundling and compression. Once
configured, a Facelets tag library is used to reference the bundles
previously defined.
These tags will work differently in development and production modes
(which are set by a flag in the properties file). When in development
mode, links to the separate, uncompressed modules are generated so that
we can debug them using, say, Firebug. Each links gets a random
parameter added to the URL so that upon every refresh of our page the
browser is force to reload the script. On the other hand, in production
mode links to the bundled, minified and compressed version of the
scripts are generated. There is no need to change anything in the pages
for this to happen, only a flag switch in the properties file is needed.
Other interesting features are traditional and Grails web apps support,
the ability to define custom postprocessors to change dynamically the
contents of bundled scripts, the ability to define global bundles that
are always imported into pages automatically, defining bundles which
are included within a defined conditional comment for MSIE, obfuscating
the scripts, etc...
Jawr has an Apache 2.0 license, and can be configured to use JSmin or
the YUI Compressor under the hood, both with a BSD style license.
regards,
Jordi Hernandez Selles
