About

Ever searched for a simple configuration, that lets you use your jetty-maven-plugin as you are used to, while working with LESS to simplify your stylesheets?

You cannot do both, use the Client-side mode of LESS to ease development and use the lesscss-maven-plugin 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:

Ever searched for a simple configuration, that lets you use your jetty-maven-plugin as you are used to, while working with LESS to simplify your stylesheets?

   
-  <link rel="stylesheet/less" type="text/css" href="styles.less" />
+  <link rel="stylesheet" type="text/css" href="styles.css" />
   <script src="../less.js" type="text/javascript"></script>

While, for the pre-compiled mode, you want to link to your stylesheets as usual, with:

   
-  <link rel="stylesheet/less" type="text/css" href="styles.css" />
+  <link rel="stylesheet" type="text/css" href="styles.css" />

While looking for a solution to this dilemma, I stumbled accross wro4j. 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.

@@ -50,13 +49,13 @@


   <groups xmlns="http://www.isdc.ro/wro">
     <group name="base">
-      <css>/less/base/*.less</css>
+      <css>/css/base/*.css</css>
     </group>

wro4j looks for /less/base/*.less inside the root of the web-context, which is equal to src/main/webapp in a normal maven-project. There are other ways to specifie the resources, 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.

wro4j looks for /css/base/*.css inside the root of the web-context, which is equal to src/main/webapp in a normal maven-project. There are other ways to specifie the resources, 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.

wro.properties

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 *.less-sources into CSS and do that on every request:

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 *.css-sources into CSS and do that on every request:

   
   preProcessors=less4j
@@ -205,7 +204,7 @@

The filter processes any URI’s that end with .css. This way, the wro4j servlet-filter makes base.css available under any path, because for exampl /base.css, /css/base.css and /foo/bar/base.css all end with .css.

This is all, that is needed to develop with dynamically reloadable compiled LESS-resources. Just fire up your browser and browse to /what/you/like/base.css. (But do not forget to put some LESS-files in src/main/webapp/less/base/ first!)

Step 3: Install wro4j-maven-plugin

All that is left over to configure now, is the build-process. If you would build and deploy your webapp now, the CSS-file base.css 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 wro4j-maven-plugin. I am using this configuration:

@@ -253,7 +252,7 @@
           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 list of available Processors!