I spent part of the week reading the JSR-168 spec. (Yes, the WHOLE thing.
The HD in my PC crashed so I had some time to kill waiting for a
replacement. Anyway...)
The spec continually mentions that the portlet generates "markup". Examples
given are HTML, XHTML, and WML. Jetspeed currently seems to favor Velocity
for portlet creation. In Jetspeed's current model, the portlet Java class
populates the context and then Velocity is used to integrate the context
variables with markup (HTML).
I see a few ways Velocity could continue to be used in JSR-168's new
paradigm:
1. The portlet generates no markup and continues to just populate the
context and other variables. The portlet container then runs the Velocity
macro generating the final markup. In this case, the portal receives the
expected final markup and displays it. This may violate the
portlet->container interface outlined in the spec; I believe portlets are
expected to return markup to the container.
2. Almost like the above, except in this case the Portal applies the final
Velocity macro. i.e. the portlets actually generate no markup, but the
container passes all the context info to the portal. This seems to be a
violation of the portlet spec contract.
3. A special JSR-168 Velocity Portlet is used which runs the Velocity code.
One of the parameters for the portlet is the Velocity macro to run. The
portlet populates the context, then applies the Velocity, then returns the
markup to the container and on up to the Portal.
Another thing I noticed in the spec. It never says the markup returned by
the portlet is what is finally to be delivered to the client. So, I could
see portlets designed to return some form of XML which the Container or
Portal then applies a final transformation on before delivering to the
client. I think this would be very analogous to calling a SOAP service or
servlet and then applying XSLT to generate HTML. Seems a bit round-a-bout,
I think the whole idea behind the portlet spec is to have the portlets
generate what will be displayed on the client.
Am I saying anything interesting here? Having just plowed through the spec
I'm trying to let thoughts swirl around and gel into understanding.
Is there a good public place where JSR-168 is being discussed? I didn't
find any discussion in the Usenet newsgroups via Google. The jsr-168
comments email address is nice, but the comments just go into a black hole
for the the committee to discuss, not those of us on the outside.
- Jasen.
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