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- <h1 class="entry-title">Combining jetty-maven-plugin and wro4j-maven-plugin for Dynamic Reloading of LESS-Resources</h1>
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- Posted on <a href="http://juplo.de/combining-jetty-maven-plugin-and-wro4j-maven-plugin-for-dynamic-reloading-of-less-resources/" title="12:58" rel="bookmark"><time class="entry-date" datetime="2013-12-06T12:58:17+00:00">December 6, 2013</time></a><span class="byline"> by <span class="author vcard"><a class="url fn n" href="http://juplo.de/author/kai/" title="View all posts by Kai Moritz" rel="author">Kai Moritz</a></span></span>
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- <p>Ever searched for a simple configuration, that lets you use your <a href="http://wiki.eclipse.org/Jetty/Feature/Jetty_Maven_Plugin" onclick="javascript:_gaq.push(['_trackEvent','outbound-article','http://wiki.eclipse.org']);" title="See the documentation for mor information">jetty-maven-plugin</a> as you are used to, while working with <a href="http://www.lesscss.org/" onclick="javascript:_gaq.push(['_trackEvent','outbound-article','http://www.lesscss.org']);" title="See LESS CSS documentation for mor informations">LESS</a> to simplify your stylesheets?</p>
- <p>You cannot do both, use the <a href="http://www.lesscss.org/#usage" onclick="javascript:_gaq.push(['_trackEvent','outbound-article','http://www.lesscss.org']);" title="More about the client-side usage of LESS">Client-side mode</a> of LESS to ease development and use the <a href="https://github.com/marceloverdijk/lesscss-maven-plugin" onclick="javascript:_gaq.push(['_trackEvent','outbound-article','http://github.com']);" title="Homepage of the official LESS CSS maven plugin">lesscss-maven-plugin</a> to automatically compile the LESS-sources into CSS for production. That does not work, because your stylesheets must be linked in different ways if you are switching between the client-side mode – which is best for development – and the pre-compiled mode – which is best for production. For the client-side mode you need something like:</p>
- <pre class="prettyprint linenums">
- <code class="html">
- <link rel="stylesheet/less" type="text/css" href="styles.less" />
- <script src="less.js" type="text/javascript"></script>
- </code>
- </pre>
- <p>While, for the pre-compiled mode, you want to link to your stylesheets as usual, with:</p>
- <pre class="prettyprint linenums">
- <code class="html">
- <link rel="stylesheet" type="text/css" href="styles.css" />
- </code>
- </pre>
- <p>While looking for a solution to this dilemma, I stumbled accross <a href="https://code.google.com/p/wro4j/" onclick="javascript:_gaq.push(['_trackEvent','outbound-article','http://code.google.com']);" title="See the documentation of ths wounderfull tool">wro4j</a>. Originally intended, to speed up page-delivery by combining and minimizing multiple resources into one through the use of a servlet-filter, this tool also comes with a maven-plugin, that let you do the same offline, while compiling your webapp.</p>
- <p>The idea is, to use the <a href="http://code.google.com/p/wro4j/wiki/MavenPlugin" onclick="javascript:_gaq.push(['_trackEvent','outbound-article','http://code.google.com']);" title="See the documentation of hte wro4j-maven-plugin">wro4j-maven-plugin</a> to compile and combine your LESS-sources into CSS for production and to use the <a href="http://code.google.com/p/wro4j/wiki/Installation" onclick="javascript:_gaq.push(['_trackEvent','outbound-article','http://code.google.com']);" title="See how to configure the filter">wro4j filter</a>, to dynamically deliver the compiled CSS while developing. This way, you do not have to alter your HTML-code, when switching between development and production, because you always link to the CSS-files.</p>
- <p>So, lets get dirty!</p>
- <h2>Step 1: Configure wro4j</h2>
- <p>First, we configure <strong>wro4j</strong>, like as we want to use it to speed up our page. The details are explained and linked on wro4j’s <a href="http://code.google.com/p/wro4j/wiki/GettingStarted" onclick="javascript:_gaq.push(['_trackEvent','outbound-article','http://code.google.com']);" title="Visit the Getting-Started-Page">Getting-Started-Page</a>. In short, we just need two files: <strong>wro.xml</strong> and <strong>wro.properties</strong>.</p>
- <h3>wro.xml</h3>
- <p>wro.xml tells wro4j, which resources should be combined and how the result should be named. I am using the following configuration to generate all LESS-Sources beneath <code>base/</code> into one CSS-file called <code>base.css</code>:</p>
- <pre class="prettyprint linenums">
- <code class="xml">
- <groups xmlns="http://www.isdc.ro/wro">
- <group name="base">
- <css>/less/base/*.less</css>
- </group>
- </code>
- </pre>
- <p>wro4j looks for <code>/less/base/*.less</code> inside the root of the web-context, which is equal to <code>src/main/webapp</code> in a normal maven-project. There are <a href="http://code.google.com/p/wro4j/wiki/ResourceTypes" onclick="javascript:_gaq.push(['_trackEvent','outbound-article','http://code.google.com']);" title="See the resource locator documentation of wro4j for more details">other ways to specifie the resources</a>, which enable you to store them elswhere. But this approach works best for our goal, because the path is understandable for both: the wro4j servlet-filter, we are configuring now for our development-environment, and the wro4j-maven-plugin, that we will configure later for build-time compilation.</p>
- <h3>wro.properties</h3>
- <p>wro.properties in short tells wro4j, how or if it should convert the combined sources and how it should behave. I am using the following configuration to tell wro4j, that it should convert <code>*.less</code>-sources into CSS and do that on <em>every request</em>:</p>
- <pre class="prettyprint linenums">
- <code class="properties">
- preProcessors=less4j
- disableCache=true
- </code>
- </pre>
- <p>You can do a lot more here. There are countless <a href="http://code.google.com/p/wro4j/wiki/ConfigurationOptions" onclick="javascript:_gaq.push(['_trackEvent', 'outbound-article', 'http://code.google.com']);" title="See all configuration options">configuration options</a> to fine-tune the behaviour of wro4j. The <code>disableCache=true</code> is crucial, because we would not see the changes take effect when developing with <strong>jetty-maven-plugin</strong> later on. You can also do much more with your resources here, for example <a href="https://code.google.com/p/wro4j/wiki/AvailableProcessors" onclick="javascript:_gaq.push(['_trackEvent', 'outbound-article', 'http://code.google.com']);" title="See all available processors">minimizing</a>. But for our goal, we are now only intrested in the compilation of our LESS-sources.</p>
- <h2>Step 2: Configure the wro4j servlet-filter</h2>
- <p>Configuring the filter in the <strong>web.xml</strong> is easy. It is explained in wro4j’s <a href="https://code.google.com/p/wro4j/wiki/Installation" onclick="javascript:_gaq.push(['_trackEvent', 'outbound-article', 'http://code.google.com']);" title="See the installation instructions for the wro4j servlet-filter">installation-insctuctions</a>. But the trick is, that we do not want to configure that filter for the production-version of our webapp, because we want to compile the resources offline, when the webapp is build. To acchieve this, we can use the <code><overrideDescriptor></code>-Parameter of the <a href="http://wiki.eclipse.org/Jetty/Feature/Jetty_Maven_Plugin#Configuring_Your_WebApp" onclick="javascript:_gaq.push(['_trackEvent', 'outbound-article', 'http://wiki.eclipse.org']);" title="Read more about the configuration of the jetty-maven-plugin">jetty-maven-plugin</a>.</p>
- <h2><overrideDescriptor></h2>
- <p>This parameter lets you specify additional configuration options for the web.xml of your webapp. I am using the following configuration for my jetty-maven-plugin:</p>
- <pre class="prettyprint linenums">
- <code class="xml">
- <plugin>
- <groupId>org.eclipse.jetty</groupId>
- <artifactId>jetty-maven-plugin</artifactId>
- <configuration>
- <webApp>
- <overrideDescriptor>${project.basedir}/src/test/resources/jetty-web.xml</overrideDescriptor>
- </webApp>
- </configuration>
- <dependencies>
- <dependency>
- <groupId>ro.isdc.wro4j</groupId>
- <artifactId>wro4j-core</artifactId>
- <version>${wro4j.version}</version>
- </dependency>
- <dependency>
- <groupId>ro.isdc.wro4j</groupId>
- <artifactId>wro4j-extensions</artifactId>
- <version>${wro4j.version}</version>
- <exclusions>
- <exclusion>
- <groupId>javax.servlet</groupId>
- <artifactId>servlet-api</artifactId>
- </exclusion>
- <exclusion>
- <groupId>org.apache.commons</groupId>
- <artifactId>commons-lang3</artifactId>
- </exclusion>
- <exclusion>
- <groupId>commons-io</groupId>
- <artifactId>commons-io</artifactId>
- </exclusion>
- <exclusion>
- <groupId>commons-pool</groupId>
- <artifactId>commons-pool</artifactId>
- </exclusion>
- <exclusion>
- <groupId>org.springframework</groupId>
- <artifactId>spring-web</artifactId>
- </exclusion>
- <exclusion>
- <groupId>com.google.code.gson</groupId>
- <artifactId>gson</artifactId>
- </exclusion>
- <exclusion>
- <groupId>com.google.javascript</groupId>
- <artifactId>closure-compiler</artifactId>
- </exclusion>
- <exclusion>
- <groupId>com.github.lltyk</groupId>
- <artifactId>dojo-shrinksafe</artifactId>
- </exclusion>
- <exclusion>
- <groupId>org.jruby</groupId>
- <artifactId>jruby-core</artifactId>
- </exclusion>
- <exclusion>
- <groupId>org.jruby</groupId>
- <artifactId>jruby-stdlib</artifactId>
- </exclusion>
- <exclusion>
- <groupId>org.jruby</groupId>
- <artifactId>jruby-stdlib</artifactId>
- </exclusion>
- <exclusion>
- <groupId>me.n4u.sass</groupId>
- <artifactId>sass-gems</artifactId>
- </exclusion>
- <exclusion>
- <groupId>nz.co.edmi</groupId>
- <artifactId>bourbon-gem-jar</artifactId>
- </exclusion>
- <exclusion>
- <groupId>org.codehaus.gmaven.runtime</groupId>
- <artifactId>gmaven-runtime-1.7</artifactId>
- </exclusion>
- <exclusion>
- <groupId>org.webjars</groupId>
- <artifactId>jshint</artifactId>
- </exclusion>
- <exclusion>
- <groupId>org.webjars</groupId>
- <artifactId>less</artifactId>
- </exclusion>
- <exclusion>
- <groupId>org.webjars</groupId>
- <artifactId>emberjs</artifactId>
- </exclusion>
- <exclusion>
- <groupId>org.webjars</groupId>
- <artifactId>handlebars</artifactId>
- </exclusion>
- <exclusion>
- <groupId>org.webjars</groupId>
- <artifactId>coffee-script</artifactId>
- </exclusion>
- <exclusion>
- <groupId>org.webjars</groupId>
- <artifactId>jslint</artifactId>
- </exclusion>
- <exclusion>
- <groupId>org.webjars</groupId>
- <artifactId>json2</artifactId>
- </exclusion>
- <exclusion>
- <groupId>org.webjars</groupId>
- <artifactId>jquery</artifactId>
- </exclusion>
- </exclusions>
- </dependency>
- </dependencies>
- </plugin>
- </code>
- </pre>
- <p>The dependencies to <strong>wro4j-core</strong> and <strong>wro4j-extensions</strong> are needed by jetty, to be able to enable the filter defined below. Unfortunatly, one of the transitive dependencies of <code>wro4j-extensions</code> triggers an uggly error when running the jetty-maven-plugin. Therefore, all unneeded dependencies of <code>wro4j-extensions</code> are excluded, as a workaround for this error/bug.</p>
- <h2>jetty-web.xml</h2>
- <p>And my jetty-web.xml looks like this:</p>
- <pre class="prettyprint linenums">
- <code class="xml">
- <?xml version="1.0" encoding="UTF-8"?>
- <web-app xmlns="http://java.sun.com/xml/ns/javaee"
- xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
- xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
- version="2.5">
- <filter>
- <filter-name>wro</filter-name>
- <filter-class>ro.isdc.wro.http.WroFilter</filter-class>
- </filter>
- <filter-mapping>
- <filter-name>wro</filter-name>
- <url-pattern>*.css</url-pattern>
- </filter-mapping>
- </web-app>
- </code>
- </pre>
- <p>The filter processes any URI’s that end with <code>.css</code>. This way, the wro4j servlet-filter makes <code>base.css</code> available under any path, because for exampl <code>/base.css</code>, <code>/css/base.css</code> and <code>/foo/bar/base.css</code> all end with <code>.css</code>.</p>
- <p>This is all, that is needed to develop with dynamically reloadable compiled LESS-resources. Just fire up your browser and browse to <code>/what/you/like/base.css</code>. (But do not forget to put some LESS-files in <code>src/main/webapp/less/base/</code> first!)</p>
- <h2>Step 3: Install wro4j-maven-plugin</h2>
- <p>All that is left over to configure now, is the build-process. If you would build and deploy your webapp now, the CSS-file <code>base.css</code> would not be generated and the link to your stylesheet, that already works in our jetty-maven-plugin environment would point to a 404. Hence, we need to set up the <strong>wro4j-maven-plugin</strong>. I am using this configuration:</p>
- <pre class="prettyprint linenums">
- <code class="xml">
- <plugin>
- <groupId>ro.isdc.wro4j</groupId>
- <artifactId>wro4j-maven-plugin</artifactId>
- <version>${wro4j.version}</version>
- <configuration>
- <wroManagerFactory>ro.isdc.wro.maven.plugin.manager.factory.ConfigurableWroManagerFactory</wroManagerFactory>
- <cssDestinationFolder>${project.build.directory}/${project.build.finalName}/css/</cssDestinationFolder>
- </configuration>
- <executions>
- <execution>
- <phase>package</phase>
- <goals>
- <goal>run</goal>
- </goals>
- </execution>
- </executions>
- </plugin>
- </code>
- </pre>
- <p>I connected the <code>run</code>-goal with the <code>package</code>-phase, because the statically compiled CSS-file is needed only in the final war. The <code>ConfigurableWroManagerFactory</code> tells wro4j, that it should look up further configuration options in our <code>wro.properties</code>-file, where we tell wro4j, that it should compile our LESS-resources. The <code><cssDestinationFolder></code>-tag tells wro4j, where it should put the generated CSS-file. You can adjust that to suite your needs.</p>
- <p>That’s it: now the same CSS-file, which is created on the fly by the wro4j servlet-filter when using <code>mvn jetty:run</code> and, thus, enables dynamic reloading of our LESS-resources, is generated during the build-process by the wro4j-maven-plugin.</p>
- <h2>Cleanup and further considerations</h2>
- <h3>lesscss-maven-plugin</h3>
- <p>If you already compile your LESS-resources with the lesscss-maven-plugin, you can stick with it and skip step 3. But I strongly recommend giving wro4j-maven-plugin a try, because it is a much more powerfull tool, that can speed up your final webapp even more.</p>
- <h3>Clean up your mess </h3>
- <p>With a configuration like the above one, your LESS-resources and wro4j-configuration-files will be packed into your production-war. That might be confusing later, because neither wro4j nor LESS is used in the final war. You can add the following to your <code>pom.xml</code> to exclude these files from your war for the sake of clarity:</p>
- <pre class="prettyprint linenums">
- <code class="xml">
- <plugin>
- <artifactId>maven-war-plugin</artifactId>
- <configuration>
- <warSourceExcludes>
- WEB-INF/wro.*,
- less/**
- </warSourceExcludes>
- </configuration>
- </plugin>
- </code>
- </pre>
- <h3>What’s next?</h3>
- <p>We only scrached the surface, of what can be done with wro4j. Based on this configuration, you can easily enable additional features to fine-tune your final build for maximum speed. You really should take a look at the <a href="https://code.google.com/p/wro4j/wiki/AvailableProcessors" onclick="javascript:_gaq.push(['_trackEvent', 'outbound-article', 'http://code.google.com']);" title="Available Processors">list of available Processors</a>!</p>
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