Pluto 2.0 Refactoring Initiative
--------------------------------
Key: PLUTO-481
URL: https://issues.apache.org/jira/browse/PLUTO-481
Project: Pluto
Issue Type: Improvement
Components: portlet container
Reporter: David Sean Taylor
Assignee: Dennis Dam
Fix For: 2.0.0
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.
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.
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.
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.
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
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.
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).
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