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From Carsten Ziegeler <cziege...@apache.org>
Subject Re: Embeddable Pluto 2.0 container for Jetspeed-2
Date Tue, 12 Feb 2008 07:44:01 GMT
Some time ago I tried upgrading the Cocoon portal to Pluto 1.1.x but as 
everything is different compared to 1.0.1 I simply stopped the migration.

Without going into all the details the proposed changes sound very good 
to me. Cocoon uses its own OM classes and own servlet for calling 
portlets as well, so these seem to be substantial requirements.

I don't think that we really need to care that much about compatibility 
to 1.1.x - it's a 2.0 version :) Of course we should try to be as 
compatible as possible.

I haven't done anything with Pluto for a long time, the only code base I 
know is 1.0.x :(

Carsten

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.
> 
> 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).
> 
> So please, provide feedback and ideas how to solve these issues. And 
> suggestions for alternative solutions will very much appreciated too!
> 
> With kind regards,
> 
> Dennis Dam
> David Sean Taylor
> Ate Douma
> 
> 
> 


-- 
Carsten Ziegeler
cziegeler@apache.org

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