Adding Document Library Views to Alfresco Share

Overview

In this post we’ll go through how to develop and deploy additional view types beyond the default simple and detailed views in the document library in Share.

The techniques here require Alfresco 4.0.2 or later, or a recent checkout of community HEAD.

The Document Library Component

We won’t go into all the details on how the document library is rendered but it’s a fairly standard webscript-based component with ‘server-side’ resources like FreeMarker files for HTML fragments, Javascript for manipulating the data model, and localization properties files, and ‘client-side’ resources sent to the browser like CSS and Javascript.

While adding a document library view will involve changes to both client-side and server-side tiers, most of our notable changes will be to client-side Javascript files sent to the browser. The server-side webscripts changes are primarily to load and instantiate the client-side objects.

The component we’re interested in is at:
alfresco/site-webscripts/org/alfresco/components/documentlibrary/documentlist.*

and note that within that directory resources from include/documentlist.* are included by some of the primary files.

DocumentList and DocumentListViewRenderer

The DocumentList Javascript object makes up the bulk of the document library view and is defined in the client-side documentlist.js file along with event handler methods and other display setup. The DocumentList object sets up a YUI DataTable which handles most of the work of AJAX calls, pagination, etc.

Each column in the DataTable is assigned a method which dictates how to render that column given the data row.  For example, the DataTable calls DocumentList.fnRenderCellThumbnail for the ‘thumbnail’ column of each row it renders.

The DocumentList also contains a set of registered DocumentListViewRenderers, ‘simple‘ and ‘detailed‘ by default, which do the work of generating the HTML for their view type. In other words, DocumentList.fnRenderCellThumbnail actually determines the current view renderer based on the current viewRendererName and hands off its work to DocumentListViewRenderer.renderCellThumbnail.

This allows developers to create their own objects which extend and override the DocumentListViewRenderer with methods for their specific needs.

For this example our goal will be to add a view which is very similar to the existing detail view but with larger thumbnails.

Steps to Add a View

Define the View

For a new view we need to define a new DocumentListViewRenderer object.  That customization could be just a new instance of the base DocumentListViewRenderer with a different name so that alternate CSS is applied and metadata rendered.

The name of the view renderer specified in the constructor is used for CSS class names among other things so a simple example of adding a second detailed view with a larger thumbnail might look like:

new Alfresco.DocumentListViewRenderer("large");

In more complex scenarios you probably want to extend DocumentListViewRenderer in a client-side documentlist-custom.js file, which is what we’ll do in this example.

First we want to define a constructor:

Alfresco.DocumentListLargeViewRenderer = function(name)
{
   Alfresco.DocumentListLargeViewRenderer.superclass.constructor.call(this, name);
   // Defaults to large but we'll copy the metadata from detailed view
   this.metadataBannerViewName = "detailed";
   this.metadataLineViewName = "detailed";
   this.thumbnailColumnWidth = 200;
   return this;
};

then make it extend from DocumentListViewRenderer:

YAHOO.extend(Alfresco.DocumentListLargeViewRenderer, Alfresco.DocumentListViewRenderer);

and we’ll override the renderCellThumbnail method with almost the same code in the detail view, but adding a documents-large CSS class to the thumbnail container and changing the call to generateThumbnailUrl to use the imgpreview thumbnail definition:

Alfresco.DocumentList.generateThumbnailUrl(record, 'imgpreview')

(Full code)

Register the View

Once the view renderer has been defined it needs to be registered with the DocumentList object via its registerViewRenderer method.  This needs to be done after the DocumentList object has been created and setup, so a good place to perform the registration is after the YUI Bubbling Event postSetupViewRenderers has fired.  To register the same view above:

YAHOO.Bubbling.subscribe("postSetupViewRenderers", function(layer, args) {
   var scope = args[1].scope;
   var largeViewRenderer = new Alfresco.DocumentListLargeViewRenderer("large");
   scope.registerViewRenderer(largeViewRenderer);
});
Accessing the View

The user has to be able to navigate to this new view and even though we’ve registered it, the DocumentList needs to know which view renderers are enabled and in what order, both of which are defined in the DocumentList’s options under viewRendererNames.  We can add our custom view above to the server-side FreeMarker model:

model.viewRendererNames.push("large");

Note that the name here must match the name of the view renderer constructor.

Not only does this define that the ‘large‘ view is enabled, the navigation buttons are also rendered from this viewRendererNames list, so we’ve taken care of the interface as well.

CSS

Our overridden renderCellThumbnail method above adds the documents-large CSS class so we’ll need to define that, as well as the display of the view selection button. Here’s a portion of the documentlist-custom.css file:

.doclist .thumbnail.documents-large {
	height: 200px !important;
	width: 200px !important;
}
.doclist .thumbnail.documents-large img {
    max-width: 280px;
}

Packaging

There are of course a number of ways this code could be packaged and deployed but this type of customization lends itself particularly well to a share extensibility module which Erik Winlöf and David Draper have blogged about in detail.  We’ll assume a standard Maven or Gradle Java project layout for the code, and to keep things simple the example deploys as a Share jar rather than an AMP.

Server-side Resources

We need to define the customization itself:

src/main/resources/alfresco/site-data/extensions/custom-view-renderer.xml

<extension>
    <modules>

        <module>
            <id>Example :: Document List Custom View</id>
            <auto-deploy>true</auto-deploy>
            <customizations>
                <customization>
                    <targetPackageRoot>org.alfresco</targetPackageRoot>
                    <sourcePackageRoot>com.example.alfresco-share-doclib-views-example</sourcePackageRoot>
                </customization>
            </customizations>
        </module>

    </modules>
</extension>

We could place the javascript which creates the new view renderer a number of places, even purely client-side, but as we’ll see in another post it can be handy to have access to the FreeMarker data model so we’ll place it in:

src/main/resources/alfresco/site-webscripts/com/example/alfresco-share-doclib-views-example/components/documentlibrary/documentlist.get.html.ftl

Note that the the wrapping <@markup> directive there indicates that we want to inject the Javascript after documentListContainer.

We’ll place the server-side webscript javascript which enables the view at:

src/main/resources/alfresco/site-webscripts/com/example/alfresco-share-doclib-views-example/components/documentlibrary/documentlist.get.js

which will get its label from the localization file at:
src/main/resources/alfresco/site-webscripts/com/example/alfresco-share-doclib-views-example/components/documentlibrary/documentlist.get.properties

Client-side Resources

For including client-side CSS, Javascript, and image resources in a jar we’ll place them in the META-INF dir at:
src/main/resources/META-INF/alfresco-share-doclib-views-example/components/documentlibrary/*

So at this point src/main/resources should look like:

Package that as jar or AMP and deploy to your Share instance.

Results

The next time you go to a site’s document library you should see the additional
button for your view and the larger thumbnails:

Since we implemented this as a standard extensibility module you can completely disable it by going to your Share deployment’s module management page at something like http://localhost:8080/share/page/modules/deploy and disable the module.

What’s Next?

I’ll go into more advanced customizations in future posts, but in the meantime, what kind of doclib view are you going to build?

Inconsistent CMIS Query Results? It’s not You, It’s your Locale.

A simple CMIS query like:

SELECT D.* FROM cmis:document AS D WHERE D.cmis:name LIKE '%Flower%' OR D.cmis:contentStreamFileName LIKE '%Flower%'

was giving me a fit lately, not working at all in RightsPro‘s CMIS plugin which uses OpenCMIS and yielding inconsistent results in CMIS Workbench where re-posting the same query ten times would give the expected result maybe half the time.

Thanks to Florian Müller and this post, it seems as though Alfresco doesn’t always behave as expected when the locale is set in the CMIS session.

Removing the locale session parameters got things working in RightsPro, but I didn’t immediately see an easy way to change the locale in a Workbench session (the log shows that it’s using a default of en_US), and I still don’t know what’s up with the inconsistent results there, perhaps a coincidental caching issue.

This was all using OpenCMIS 0.3 against Alfresco Enterprise 3.3.1 over SSL.

Searching Custom Aspects via CMIS

I didn’t immediately see any simple, working examples of how to search custom aspect properties via CMIS so I’ll post a brief one here.

The Aspect

In this example we’re using a CMIS query to search for the IPTC caption property provided by the IPTC/EXIF project. After installing that module the properties are applied using an aspect which is defined in $ALFRESCO_HOME/WEB-INF/classes/alfresco/module/iptcexif/model/iptcModel.xml.

Within that file you’ll see:

    <aspects>
      <aspect name="iptc:iptc">

The Query

In our case the target Alfresco repository is running enterprise 3.3.1 and aspects are implemented via JOIN syntax as very briefly stated in the wiki.

So the resulting query for this particular search of the IPTC caption field ends up looking like:

SELECT D.*, IPTC.* FROM cmis:document AS D JOIN iptc:iptc AS IPTC ON D.cmis:objectId = IPTC.cmis:objectId WHERE IPTC.iptc:caption LIKE '%searchTerm%'

The Changes

There were big changes in Alfresco 3.4 in terms of metadata extraction and I haven’t yet had a chance to update the forge projects (or determine if they’re still even needed) and there are proposals for aspects in the next CMIS spec so I’ll be back to update this post.

Render Me This: Video Thumbnails in Alfresco 3.3

Alfresco has undergone quite a few changes under the hood in version 3.3, including refactoring of the ThumbnailService to make use of the RenditionService, which I had to explore in a recent deep dive to get video working for the thumbnails extension. This is obviously a subject dear to your heart as well or you would have moved on by now.

Alfresco 3.1.

Let’s take a look at how things worked back in the old days, before 3.2 (fuzzy 2009 dream sequence begins…)

You most likely kicked things off with a thumbnail generating URL which would hit a ScriptNode.createThumbnail method which looked up the thumbnailDefinition and called the ThumbnailService with the TransformationOptions contained in the definition.

The ThumbnailService then told the ContentService to perform the transformation which looked up the ContentTransformer from the TransformerRegistry and executed transformer.transform which usually delegated to a RuntimeExec object to perform the actual command line transformation.

If we were to visualize the key elements of that stack for a synchronous video thumbnail creation it would look something like:

  • org.alfresco.repo.jscript.ScriptNode.createThumbnail
    • org.alfresco.repo.thumbnail.ThumbnailRegistry.getThumbnailDefinition (loads TransformationOptions)
    • org.alfresco.repo.thumbnail.ThumbnailServiceImpl.createThumbnail
      • org.alfresco.repo.content.ContentServiceImpl.transform
        • org.alfresco.repo.content.transform.ContentTransformerRegistry.getTransformer
        • org.alfresco.repo.content.transform.ContentTransformer.transform
          • TempFileProvider.createTempFile
          • org.alfresco.util.exec.RuntimeExec.execute
            • ffmpeg …

Well now, that’s not so bad.

Alfresco 3.3.

These Alfresco people don’t mess around. If it’s determined that refactoring should happen, it happens, real damn quick, even if it’s huge. To that end subsystems were rolled out in 3.2 and the RenditionService was introduced in 3.3.

Subsystems. Certain content transformers, like ImageMagick, have been refactored as a subsystem, which is cool. Read the wiki page to get the full story but in short it’s a much more flexible architecture.

The ffmpeg video transformer contained in the latest release of the thumbnails extension follows this precedence and has been refactored as a subsystem, so there.

RenditionService. I wouldn’t say I hate it, but this package should be wary of eating crackers in bed, or maybe I’m just not familiar enough with it yet.

The new rendition service utilizes RenditionDefinitions which require that any TransformationOptions be ‘serialized’ into a parameter map, which are then reassembled into TransformationOptions objects before being passed to the ContentTransformer. I suppose this is done to make it easier to do things like hand renditions off to another server in a cluster, but it’s a bit of a pain in the ass for developers.

So, back to our synchronous video thumbnail creation scenario (deep breath), the ThumbnailService now creates a RenditionDefinition which it passes to the RenditionService which wraps things up in a PerformRenditionActionExecuter that gets passed to the ActionService. The PerformRenditionActionExecuter calls the ActionService again which loads the RenderingEngine from the spring ApplicationContext. A RenderingEngine is itself an ActionExecuter so the ActionService calls execute which calls render which proceeds to rebuild the TransformationOptions object needed by the ContentService to get the proper ContentTransformer so transformer.transform can use a RuntimeExec object to perform the actual command line transformation.

The key elements of our pseudo stack/method trace would look like:

  • org.alfresco.repo.jscript.ScriptNode.createThumbnail
    • org.alfresco.repo.thumbnail.ThumbnailRegistry.getThumbnailDefinition (loads TransformationOptions)
    • org.alfresco.repo.thumbnail.ThumbnailServiceImpl.createThumbnail
      • org.alfresco.repo.thumbnail.ThumbnailServiceImpl.createRenditionDefinition
        • org.alfresco.repo.thumbnail.ThumbnailRegistry.getThumbnailRenditionConvertor().convert(transformationOptions, assocDetails) <- this serializes the transformationOptions into a parameter map
      • org.alfresco.repo.rendition.RenditionServiceImpl.render
        • org.alfresco.repo.rendition.RenditionServiceImpl.createAndExecuteRenditionAction
          • org.alfresco.repo.action.ActionServiceImpl.createAction(PerformRenditionActionExecuter.NAME)
          • set the renditionDefintion on performRenditionAction
          • org.alfresco.repo.action.ActionServiceImpl.executeAction
            • org.alfresco.repo.action.ActionServiceImpl.directActionExecution
              • load ActionExecuter from applicationContext
              • org.alfresco.repo.rendition.executer.ImageRenderingEngine.execute
                • org.alfresco.repo.rendition.executer.ImageRenderingEngine.render
                  • org.alfresco.repo.rendition.executer.ImageRenderingEngine.getTransformationOptions <- rebuilds parameter map into TransformationOptions objects
                  • org.alfresco.repo.content.ContentServiceImpl.transform
                    • org.alfresco.repo.content.transform.ContentTransformerRegistry.getTransformer
                    • org.alfresco.repo.content.transform.ProxyContentTransformer.transform <- subsystems
                      • org.alfresco.repo.content.transform.ContentTransformerWorker.transform
                        • TempFileProvider.createTempFile
                        • org.alfresco.util.exec.RuntimeExec.execute
                          • ffmpeg …

that’s a spicy meatball!

A while ago we submitted an issue to Alfresco suggesting TransformationOptions which contain distinct target AND source options so that one could for example specify that all ‘doclib’ thumbnails be of max-width X and max-height Y (the type of target options currently available) and furthermore, if it’s a document take page 1 (or maybe you need a different page in your deployment) or if it’s a video take 1 frame starting 0.5 seconds in, or if it’s a layered image file take the second layer, etc. (a list of source options).

Alas, this concept of SourceTargetTransformationOptions hasn’t yet been embraced by the Alfresco team but is used by the video transformer in the thumbnails extension which made refactoring for renditions even more difficult, but you’re not here to listen to me bitch and moan, so I’ll just say that it’s done and seems to be working fine.

So, there you have it, renditions and subsystems as they relate to video thumbnails. Hit me up with any questions or things I’ve missed.