The approach we have taken to solve this problem may not solve all your customization problems immediately, but what we have implemented should pave the way for future extensibility enhancements in later releases. We've also provided an extensibility platform to provide your own solutions to the problem.
Essentially we have changed Spring Surf so that instead of writing templates directly to the output stream we write to an in-memory model and then allow extensions to manipulate that model before it gets flushed to the output stream. The mechanism for updating the model is through the use of new and updated FreeMarker template directives.
Wherever an extensibility directive is used in a bass template it can be manipulated by a corresponding extension file. There are a initial set of actions:
remove (completely remove the directive contents from the model)
replace (replace the directive contents in the model with something new)
before (place a new directive immediately before the target directive contents)
after (place new directive contents immediate after the target directive contents)
In the current code we provide 2 directives that support extensibility: <@region> and <@markup>.
The <@region> directive was used extensively in previous versions of Alfresco Share to define the Regions into which Component are bound - we have simply updated its implementation to work with the extensibility model. The <@markup> directive model is entirely new and is simply used to demarcate sections of HTML in a template.
In the first 2 blog posts I described how you can add and remove content from Alfresco Share by modifying the Components (and their Sub-Components). This approach relies on their being a Component available that will be bound to a Region in the template.
Using this alternative mechanism makes it possible to add new regions and also completely remove regions to prevent Components from being bound. This is significantly different because it is a much more volatile approach but could be useful in certain circumstances. If you want to remove some content and prevent another module from either restoring or adding to it, you can remove it entirely from the model so that it cannot be changed.
In an earlier blog I demonstrated how to add a new content to an Alfresco Share page by providing an additional Sub-Component as an extension. This could have also been done using a <@region> directive extension.
Enable Surf Bug and click on the Title bar. Note the 'Template Type' property which in this case is 'org/alfresco/dashboard'. This means that the file we need to extend is 'dashboard.ftl' in the 'org.alfresco' package.
Update the 'blog-demo.xml' file to add the following module definition:
Note that the package we've added the file to is prefixed by 'alfresco.templates'. This is the source package at which Spring Surf Class Loader starts looking for template files. It is vitally important to include this prefix to your package or your extension won't be found.
We need to create a new Component to bind to our new Region. We're going to be lazy and use the legacy configuration style (although we could use the new style, this way is shorter and suitable for our purposes).
Create a file called 'global.additional-content.xml' and place it in the 'alfresco.site-data.components' package. The file should contain the following:
Note that we're re-using the same Web Script created in the first extensibility blog. If you haven't completed the tutorial in that blog then the Component won't find the Web Script specified by the <uri> element.
Re-build and re-deploy the JAR and restart the Alfresco Share web server and you should see the additional content.
If you want to test out the other customization operations then you can update the 'dashboard.ftl' as follows:
At the time of writing there are currently no uses of the <@markup> directive anywhere in Alfresco Share. It's hoped that the Alfresco Community will make suggestions/contributions as to where they would best be added. They can wrap any section of FreeMarker source in either a WebScript or TemplateInstance to identify sections of the template that can be customized. If you have any suggestions then please post to the Community forums.