Skip to main content

Messing with the Engine

Don't ask me why -- well, ok, ask me and I'll tell you -- but I have been investigating lately how to create my own Engine instance (i.e. Tridion.ContentManager.Templating.Engine). Engine is an abstract class and as such cannot be instantiated directly. Time to get decompily...

I figured out there are a couple of implementations for Engine, but question is when is one used over the other. The simple solution was to log somehow the engine.GetType() method call in different contexts and see what comes back.

I ended up with a very simple C# Fragment:

package.PushItem("TYPE",
    package.CreateStringItem(ContentType.Text, engine.GetType()));

And its DWT counterpart:

Engine type: @@TYPE@@

The result is the following:
  • executing the template in Template Builder displays:  Tridion.ContentManager.Templating.Debugging.DebuggingEngine
  • executing in CME Preview or doing an actual publish displays :  Tridion.ContentManager.Templating.TemplatingRenderer
Creating an instance of DebuggingEngine seems like black magic, so I didn't even try. TemplatingRenderer on the other hand is doable, although very laborious:

Session session = new Session();
Page page = new Page(new TcmUri("tcm:20-102-64"), session);
Template template = new PageTemplate(new TcmUri("tcm:20-715-128"), session);
ResolvedItem resolvedItem = new ResolvedItem(page, template);

PublishInstruction publishInstruction = new PublishInstruction(session);
PublicationTarget publicationTarget = new PublicationTarget(new TcmUri("tcm:0-1-65537"), session);

RenderInstruction renderInstruction = new RenderInstruction(session) { RenderMode = Tridion.ContentManager.Publishing.RenderMode.PreviewDynamic };
RenderedItem renderedItem = new RenderedItem(resolvedItem, renderInstruction);

RenderContext renderContext = new RenderContext();

IRenderer engine = new TemplatingRenderer();
engine.Render(resolvedItem, publishInstruction, publicationTarget, renderedItem, renderContext);

If you notice, engine is in fact initialized when the Render method is executed. Weirdly, Render is a method defined by IRenderer. That is pretty weird! TemplateRenderer extends/implements both Engine and IRenderer.

The code above will in fact start the publishing of the given Page with the given Page Template. That's a bit too much from what I was intending to do in the first place.

My goal is to simply have an Engine object so that I can instantiate a Package object. It seems like the following code is enough:

Engine engine = new TemplatingRenderer();
Package package = new Package(engine);

// test it 
package.PushItem("name", package.CreateHtmlItem("value"));

This will create a new item in the Package, so I can now use the object locally without having to perform an actual publish or preview in Template Builder.

What a hack!


Comments

Chris Summers said…
Please tell us why...
Mihai Cădariu said…
For short, I wanted to be able to run templates in a stand-alone application (e.g. Console app).

For long, I wanted to play with it in my Java Mediator quickly, without having to go load the TBB in Template Builder, execute it, stop TB because it locked all my JARs/DLLs, etc.

However, I also see a strong use-case for unit testing your templates! A continuous build environment (CM side). This can be fine grained (even at TBB level). Kinda: if that's the input package, that's the output. Is it the expected one?

Pretty cool :)

Popular posts from this blog

Toolkit - Dynamic Content Queries

This post if part of a series about the  File System Toolkit  - a custom content delivery API for SDL Tridion. This post presents the Dynamic Content Query capability. The requirements for the Toolkit API are that it should be able to provide CustomMeta queries, pagination, and sorting -- all on the file system, without the use third party tools (database, search engines, indexers, etc). Therefore I had to implement a simple database engine and indexer -- which is described in more detail in post Writing My Own Database Engine . The querying logic does not make use of cache. This means the query logic is executed every time. When models are requested, the models are however retrieved using the ModelFactory and those are cached. Query Class This is the main class for dynamic content queries. It is the entry point into the execution logic of a query. The class takes as parameter a Criterion (presented below) which triggers the execution of query in all sub-criteria of a Criterio

A DD4T.net Implementation - Custom Binary Publisher

The default way to publish binaries in DD4T is implemented in class DD4T.Templates.Base.Utils.BinaryPublisher and uses method RenderedItem.AddBinary(Component) . This produces binaries that have their TCM URI as suffix in their filename. In my recent project, we had a requirement that binary file names should be clean (without the TCM URI suffix). Therefore, it was time to modify the way DD4T was publishing binaries. The method in charge with publishing binaries is called PublishItem and is defined in class BinaryPublisher . I therefore extended the BinaryPublisher and overrode method PublishItem. public class CustomBinaryPublisher : BinaryPublisher { private Template currentTemplate; private TcmUri structureGroupUri; In its simplest form, method PublishItem just takes the item and passes it to the AddBinary. In order to accomplish the requirement, we must specify a filename while publishing. This is the file name part of the binary path of Component.BinaryConten

Scaling Policies

This post is part of a bigger topic Autoscaling Publishers in AWS . In a previous post we talked about the Auto Scaling Groups , but we didn't go into details on the Scaling Policies. This is the purpose of this blog post. As defined earlier, the Scaling Policies define the rules according to which the group size is increased or decreased. These rules are based on instance metrics (e.g. CPU), CloudWatch custom metrics, or even CloudWatch alarms and their states and values. We defined a Scaling Policy with Steps, called 'increase_group_size', which is triggered first by the CloudWatch Alarm 'Publish_Alarm' defined earlier. Also depending on the size of the monitored CloudWatch custom metric 'Waiting for Publish', the Scaling Policy with Steps can add a difference number of instances to the group. The scaling policy sets the number of instances in group to 1 if there are between 1000 and 2000 items Waiting for Publish in the queue. It also sets the