Hi Eric,
Thanks for your very precise and informative response.
I also have a few comments inline of course.
Regards,
Ate
Eric Dalquist wrote:
Ate,
To introduce myself I'm a developer on the uPortal project and was one
of the people involved in upgrading from Pluto 1.0.1 to 1.1. I will say
up front it was a fair bit of work. We essentially removed the 1.0
support code and wrote the 1.1 support code from scratch. The result was
a smaller amount of code required in uPortal to make use of Pluto 1.1
with no loss in functionality and actually a gain in functionality in
many places. I have more comments in-line.
Ate Douma wrote:
Dear committers, community,
Jetspeed-2 currently still uses Pluto 1.0.1 as its JSR-168 container,
but we want and need to upgrade and migrate to the latest Pluto
container under
development, aka the not yet released Pluto 2.0 targeted as the
JSR-286 RI.
This however is currently impossible to do because of the
architectural changes Pluto underwent from version 1.0.x to 1.1.x.
Technically, viewed from the POV of an easy to embed container for the
Pluto Portal Driver, or environments which only need the
out-of-the-box features
provided, these architectural changes have resulted in a much simpler
and easier to understand and maintain model and API, and as such these
changes were great!
But... for a portal like Jetspeed-2, which provides a much enhanced
usage and feature list *on container level*, these architectural
changes have, simply put,
completely broken with the functional and technical "contract"
provided by Pluto 1.0.x and as such make it now impossible for us to
migrate to the current Pluto
container.
As it is the primary mission and goal of the Pluto project to provide
an embeddable portlet container for portals like its Apache Portals
sibling project
Jetspeed-2, it is our view (as Jetspeed-2 committers) that we need to
discuss what needs and can to be done, on both Jetspeed-2 and Pluto
side, to bring our
projects back together, and how to restore the original *functional*
contract Pluto provided with version 1.0.x.
To this end, we'll present our (short) assessment how the current
Pluto container API and implementation has changed and broken with the
old Pluto 1.0.x
features which Jetspeed-2 depends upon to be able to maintain our
current Jetspeed-2 features, as well as what we think needs to be done
*functionally* to
restore these features.
To be very clear: we're not asking nor suggesting to restore the old
Pluto 1.0.x API and SPI as is. We fully expect and are willing to
adapt Jetspeed-2 to the
new Pluto architecture as much as needed, even while that most likely
will now cause Jetspeed-2 itself to have to break with its own public
API and thus lose
(some) backwards compatibility. After all, Pluto now has had several
releases based on its new Pluto 1.1.x architecture and we (as Apache
Portals community)
have the obligation to maintain as much backwards compatibility for
the users of these versions as well.
So, what we will propose later on is to work towards a solution which
will restore the ability for Jetspeed to properly use and embed the
new Pluto 2.0
container but still maintain the lightweight and simple configuration
and usage of the container for portals like the Pluto Portal Driver
and other use-cases
without breaking its current "contract".
But first lets get down to some of the issues we have identified so
far. This is most likely not the complete list but covers the most
important ones.
The Pluto 1.0.x object model API (OM)
=====================================
Pluto 1.0.x provided a fully interface based object model to represent
the web and portlet deployment descriptors (web.xml and portlet.xml).
Through factory methods, the Pluto 1.0.x container only used these
interfaces in its implementation. That allowed Jetspeed and other
portals to supply its own
implementation of the OM and use that to provide enhanced features
like database persistence, extended meta data, caching control, etc.
Of course, Pluto 1.0.x also provided its own implementation classes of
the OM and Jetspeed uses these as base classes but provides extended
implementations to
hook them up and into its own backend and management features.
Pluto 1.1.x completely dropped all of this. Instead, a new descriptor
API was provided with a complete new set of classes (no interfaces!)
which are used and
instantiated directly within the container with no factory support or
any other way of extending the current implementation.
As such, the current container only allows usage of the web.xml and
portlet.xml descriptors and features derived from them as provided by
the container.
Furthermore, as the loading and management of the descriptors is now
done directly (and only) by the container itself, there is no way for
Jetspeed to hook into
this process anymore.
Effectively, this means that descriptor persistence, caching, custom
extensions, *standard* support for custom portlet mode or window-state
mapping,
etc. all no longer are possible with the current Pluto container. Not
just for Jetspeed but any portal needing and depending on these features.
We use make both custom portlet modes and window states available to
deployed portlets and this functions as expected in Pluto 1.1, the
descriptor objects provide information about which custom modes and
states the portlet has declared.
That information is available from the descriptor itself, true.
But in Jetspeed-2 you can additionally define a custom mapping of existing
Portal provided modes/states to the ones defined by the portlet.
For this we leverage an additional deployment descriptor which meta data is linked to the (persistent) object model representation of the standard portlet
descriptor. This extension mechanism is no longer doable with Pluto.
The Pluto 1.1.x/2.0 PortletContextManager, PortletDescriptorRegistry
and PortletServlet
=======================================================================================
With the switch to Pluto 1.1.x, the container added control and
management of the above mentioned deployment descriptors and fully
integrated them with the
container interaction which now depend on this management
*implementation*, and also hooked that up on the portlet application
context.
This means that now you need a separate container instance for each
portlet application and that the container itself loads and manages
the descriptors.
Also, interaction with the container now requires the use of the Pluto
provided PortletServlet (although that one possibly can be extended)
as it is tied to the
PortletContextManager directly (which in turn is tied to the
PortletDescriptorRegistry).
Besides the obvious problem that this effectively blocks delegating
management of the context and descriptors for the portal, it also
forces the usage and
interaction with portlets to the Pluto provided implementation.
For instance, Pluto delegates interaction to each portlet through a
separate instance of its PortletServlet, while Jetspeed currently has
its own more generic
JetspeedContainerServlet which is not tied to a single portlet. The
Jetspeed solution allows for dynamically enabling/adding portlets (as
defined in
portlet.xml) without any need to rewrite the web.xml. But using the
Pluto PortletServlet requires changing the web.xml (and thus reloading
the context) to do so.
The Pluto 1.1.x service provider interfaces (SPI)
=================================================
Although the new Pluto SPI (comprising of the
RequiredContainerServices and OptionalContainerServices) generally
provides a nice and simple interface to plugin
portal specific implementations, certain features available with Pluto
1.0.x are no longer available.
With Pluto 1.0.x, critical components as the PortletContext and
PortletWindow were accessed by the container through factory classes.
These no longer exist and the pluto container directly instantiates
its own implementations for these components.
You can provide your own PortletWindow impl. Since all container calls
require a PortletWindow (interface) all callbacks simply provide this
interface back to the handling code. We definitely have a custom
PortletWindow implementation that tracks more information than the Pluto
interface describes.
True, but onces invoked, Pluto will nonetheless *wrap* this interface inside an
instance of its own PortletWindowImpl anyway.
This implementation delegates all the interface methods to the wrapped object
itself, except getServletContext() and getPortletEntity() which it overrides.
And these two method overrides are used to hook back into the internal
container content management and descriptor registry.
That's just my point: the current container simply enforces these dependencies
and providing our own implementation of the PortletWindow will be useless.
It does look like there is no way to provide your
own PortletContext impl.
Jetspeed however very much depends on its own extensions of these
components to provide support for features like parallel rendering,
clustering and attaching
additional meta data (or even preferences) to a PortletWindow or
PortletEntity.
Additionally, while Pluto 1.0.x allowed managing multiple
PortletWindows for a PortletEntity, this *Portlet Spec* feature has
been removed from the current
Pluto 1.1.x/2.0 container.
Again, I'm not sure the need for portlet container support for this. We
use the DD objects as an easy way to know what is in the .xml objects.
We then internally have our own portlet object model with a
PortletDefinition (admin publishing a portlet), PortletEntity (user
subscribing to portlet), PortletWindow (user viewing a portlet). Each
definition can have N child entities and each entity can have N child
windows. Each level in the model provides extra configuration data that
we expose via the SPIs that we implement. We don't even bother with the
Pluto PortletEntity interface since the only thing Pluto ever asks for
is a PortletWindow.
Yeah, but what about the preferences? Pluto access the PortletWindow preferences through its *internally managed* PortletEntity. As we have no control here, we
can't put our own preferences extensions (like defined on PSML page level for instance) in place either.
Lastly, not all of services referenced through these SPI interfaces
are only accessed through it.
For instance, the OptionalContainerService.getPortletRegistryService()
is by default implemented by the PortletContextManager. But, this
implementation is very
much directly used (as static instance even) within the container.
Effectively, the interface is now only an API portals might use, but
it cannot be replaced
and thereby cannot be regarded as a proper SPI interface anymore.
This seems like a pretty big bug. While we didn't have a need for it I
can very much see where moving the descriptor service behind a true SPI
to allow implementers to write their own if they want would be a good
thing.
Thanks for your view. Although you might not need it now, that can change in
the future.
Having this fixed will help us all.
Solution
========
As indicated earlier, solving the above issues such that Pluto 2.0 can
be made embeddable again, in Jetspeed or other portals, needs to be
done in a way which
maintains backwards compatibility for current Pluto 1.1.x users.
Although we don't have a clear proposal for this, our current idea is to:
- define new OM interfaces to be implemented by the current descriptor
api classes
- enhance the OptionalContainerServices SPI to provide additional
services for loading and managing the deployment descriptors
- enhance the OptionalContainerServices SPI to provide additional
services for accessing components like PortletContext, PortletWindow etc.
- refactor the container implementation to only use the OM interfaces
- refactor the container implementation to only use the SPI provided
services and no longer directly binding to its service implementations
These all seem like great solutions and it seems to me they could be
done with very minor changes required of people that have already
implemented 1.1
That's the goal!
Reviewing this proposal and monitoring and checking the changes onces we start
performing them is and will be very helpful.
When done properly, the above changes should still allow using the
current implementation without any functional or even technical
consequence.
Now, the above changes will mean a lot of work and lots of testing as
well to make sure everything remains working as expected.
We, as primary Jetspeed committers have much at stake here so we are
definitely willing to help out and do much of the grunt work.
And of course, we will have a large amount of work to do at Jetspeed
Portal side as well: all our Pluto Factory implementations have become
useless, all Pluto
OM packages (and some interfaces) have changed, and we will need to
provide new implementations for the Pluto SPI container services.
We (uPortal Developers) can also be involved in this process to provide
the perspective of another portal that does quite a bit with hooks into
Pluto though it sounds like we do less than Jetspeed does.
Thanks!
For our implementations of the Pluto SPI container services, we will
definitely look at the current Pluto provided implementations and
where possible try to
make use of them as much as possible. To that end, we will probably
also need to be able to hook in our own extensions which might require
some additional
refactoring but should not result in functional or technical changes
of the default Pluto services.
Note: we want to migrate to Pluto 2.0 for our next Jetspeed 2.2
release. But, for that release we'll stick to only using the JSR-168
container features.
Then, for the following major release, version 2.3 which we currently
have scheduled sometime this summer, we will provide full JSR-286
compliance.
So, our initial goal is to get Pluto 2.0 working again with Jetspeed-2
but stick to our current features.
This all is clearly not something which can be done or will be ready
overnight, nor possible to do all by ourselves.
But we do need to start resolving this ASAP so it won't hold up the
release of both Pluto 2.0 and Jetspeed 2.2 longer than needed.
As said: the above proposal is still just an idea. And of course how
to do all this, is fully open for debate and we are very interested in
hearing the opinions
of other committers and community members (also from other portals
embedding Pluto 1.1.x).
So please, provide feedback and ideas how to solve these issues. And
suggestions for alternative solutions will very much appreciated too!
This sounds like a great proposal. As I've said above uPortal has
already gone through the pain (and yes there was some pain) of moving to
Pluto 1.1 but the simplification of our portlet support code was more
than worth it along with putting us in a position to more easily (we
hope) move to Pluto 2.0. I would be more than happy to talk about the
approaches uPortal has taken with using Pluto 1.1 and be involved with
discussions about these upcoming changes to Pluto 1.1 to make it as
useful as possible for other portals as well.
With kind regards,
Dennis Dam
David Sean Taylor
Ate Douma
