YUI Compressor Filter

YUI Compressor Filter for Java web applications.

This filter applies the YUI Compressor over any URLs ending with .less, .css, or .js, creating minified versions of those resources for serving to users. Once the file is processed, the result is cached to save on having to process it again. Any changes to these files will be picked up and cause the file to be processed the next time it is requested.

• Current version: 1.1.1
• Release date: 3 August 2013

Requirements

• Java 7
• A Servlet 3.0 compliant servlet container

Installation

Standalone distribution

Copy the JAR from the latest release bundle, placing it in the WEB-INF/lib directory of your web application, or build the project from the source code here on GitHub.

For Maven and Maven-compatible dependency managers

Add a dependency to your project with the following co-ordinates:

• GroupId: nz.net.ultraq.yuicompressor
• ArtifactId: yuicompressor-filter
• Version: 1.1.1

Usage

Annoyingly, the YUI Compressor uses a heavily-modified version of Rhino so you can't easily put the official distributions of Rhino into the classpath and expect things to work. To get around this, the filter launches the YUI Compressor in a separate classloader. This filter also needs to be told of the location of the YUI Compressor JAR though since you might want to have this JAR outside of the normal classpath so it doesn't interfere with existing installations of Rhino. If not specified, the filter will look in /WEB-INF/lib-sandbox/yuicompressor-2.4.7.jar, but this can be overridden by providing the necessary init parameter in your web.xml file:

<filter>
	<filter-name>YUICompressorFilter</filter-name>
	<filter-class>nz.net.ultraq.yuicompressor.YUICompressorFilter</filter-class>
	<init-param>
		<param-name>YUI_COMPRESSOR_JAR</param-name>
		<param-value>location-of/yuicompressor.jar</param-value>
	</init-param>
</filter>

If you're not taking advantage of servlet 3.0 annotations, then you'll also need to specify the filter mappings in your web.xml file:

<filter>
	<filter-name>YUICompressorFilter</filter-name>
	<filter-class>nz.net.ultraq.yuicompressor.YUICompressorFilter</filter-class>
	<init-param>
		<param-name>YUI_COMPRESSOR_JAR</param-name>
		<param-value>location-of/yuicompressor.jar</param-value>
	</init-param>
</filter>
<filter-mapping>
	<filter-name>YUICompressorFilter</filter-name>
	<url-pattern>*.less</url-pattern>
	<url-pattern>*.css</url-pattern>
	<url-pattern>*.js</url-pattern>
</filter-mapping>

Limitations

This filter only works on URLs which locate a file on the file system. This is a limitation of the way I've chosen to detect changes to the underlying file, which I've done using Java 7's NIO 2 package.

Changelog

1.1.1

• Update post-processing-filter dependency to 1.1.1

1.1

• Change package and Maven group to nz.net.ultraq.yuicompressor (dropped the 'web' part).
• Disabling the filter is now done with the -Dnz.net.ultraq.yuicompressor.DisableProcessing=true VM argument / system property.

1.0.5

• Project structure reorganization after major fixes to the Gradle build scripts.
• Changed default location of the YUI Compressor JAR to /WEB-INF/lib-sandbox/yuicompressor-2.4.7.jar since it should reside outside of the normal classpath anyway.

1.0.4

• Update post-processing-filter dependency to 1.0.2
• Minor fixes from the updated maven-support Gradle script.

1.0.3

• Switched from Ant to Gradle as a build tool.
• Made project available from Maven Central. Maven co-ordinates added to the Installation section.

1.0.2

• Allowed for filter to co-exist with existing Rhino installations.

1.0.1

• Added the ability to disable the filter from minifying resources with a system property (an annoyance when doing any client-side debugging). Just add -Dnz.net.ultraq.web.yuicompressor.DisableProcessing=true to your VM arguments.

1.0

• Initial release