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Cocoon refactorings

I've been maintaining a complex Cocoon application for a couple of years now. Unfortunately, as the code gets older, it requires more and more time for maintenance unless you keep it clean and neat from the beginning. Finally I've found time to refactor the project gradually and I'll try to keep it this way. In this article I'm going to review the steps I've taken to improve the code and build quality.

Remove duplicated resources
I've started with removing duplicated and unused resources (mostly images and icons). Many of them were duplicated across the application in several Cocoon blocks. So I had to keep common resources in a single shared block and modify references from other blocks accordingly. For this I've added the following sitemap rule into all blocks:
<map:match pattern="shared/resource/external/**">
  <map:read src="servlet:shared:/resource/external/{1}"/>
This single improvement decreased the build time by 30% (that is about 10 seconds). Besides, I've refactored CSS files by extracting common.css that is common for all blocks and have left only specific CSS rules in each block.

Remove duplicated resources - update from 18th June
I've found a much more elegant way to achieve the same. It uses ResourceExistsSelector in Cocoon. BTW, this selector is widely used for different sitemap patterns. Here is the code that I've added to all block sitemaps:
<map:match pattern="resource/external/**">
  <map:select type="resource-exists">
    <map:when test="resource/external/{1}">
      <map:read src="resource/external/{1}"/>
      <map:read src="servlet:shared:/resource/external/{1}"/>
In comparison with the method described above, this one gives you the same block-relative URL as in the shared block. It helps to prevent issues, e.g. using background images in shared CSS files. Because in this case you'd prefer a single relative URL that is valid for all blocks.

Extract sub-sitemaps
The next step was extracting sub-sitemaps using Cocoon Mounts (official doc here). This one I had in my mind for a long time. In several blocks we had good use cases for this such as separating a file generating pipeline and a test pipeline:
<map:match pattern="file/**">
  <map:mount uri-prefix="file" src="sitemap-file.xmap"/>

<map:match pattern="test/**">
  <map:mount uri-prefix="test" src="sitemap-test.xmap"/>
Ideally you should take care about it while designing your app and you'll be able to benefit from auto-mounting and dynamic mounting.

Further steps
There is much more to improve if you check the community sources:


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