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From Dan Connelly <>
Subject Re: use of jcr mapping for JSR170, in graffito
Date Wed, 30 Aug 2006 12:42:19 GMT

I have not looked at the CMS or workflow in Graffito at all.   My 
interest, for now, is in mapping objects to JCR , and in connecting 
Jackrabbit's persistence to Eclipse's design and modeling tools.    
(However, at this point my thinking is that Graffito jcr mapping is the 
prototype for for what I want, but not the solution.   Eclipse's EMF 
models are JO but not PO, that is, not POJOs, as Graffito would want.)

Ultimately, the object mapping is to support design-driven business 
reporting for portal servers (using, for instance, the Eclipse BIRT 
report server).   Originally, my interest in Graffito was in its 
integration with Jetspeed2.   J2 and Liferay are may target portals.

Whether or not a CMS (as commonly defined) is useful for portalized 
business reporting is TBD.    As I mentioned in a previous post, I have 
looked into Eclipse's new Apogee CMS project (to be transferred from 
Nuxeo).    All things being equal, I would prefer to use Apogee over 
Graffito for CMS, but (so far) I do not see good support for JCR custom 
node types in Apogee.  

If Graffito CMS is better than Apogee CMS at supporting custom node 
types or access management for objects mapped into Jackrabbit , then I 
would be glad to hear of it.    So far, I have not done this 
investigation myself.

       -- Dan

ruchi goel wrote:

> Hi Dan,
>   Thanks for detailed response . I  will  try this out  and let you 
> know my experiences.  Don't you think that the cms model should be 
> directly talking to jcr mapping tool  at least for the services which 
> are part of jsr170 (Workflow is exception).
> Another question : Is workflow implemented as a service ? I don't see 
> anything in the source tree ?
> Thanks,
> Ruchi
> Dan Connelly wrote:
>>  Hi Ruchi:
>> I am also a newcomer to Graffito (and a refugee from Eclipse Apogee).
>> What I did  to get started with jcr mapping is to Check Out the 
>> jcr-mapping code (under jcr folder) as a project in Eclipse.   With 
>> Eclispe SVN Repository perspective, the project creation is automatic 
>> on the Check Out..   A no-brainer.    (Note:  mapping itself does not 
>> require anything else from Graffito.)
>> Then you will try to run the JUnit tests (in Eclipse) from your jcr 
>> mapping project.    The tests are in the download.
>> You will need to fetch a bunch of libraries to get rid of the initial 
>> errors in this testing.   An easy way to get these libraries (most of 
>> them anyway) is to import the Jackrabbit server war (as an Eclipse 
>> Dynamic Web project) and ref its jars from your mapping project.
>> You do NOT need the graffito api at all.    The Graffito jcr mapping 
>> uses Jackrabbit directly (as far as I can tell).
>> ---------------------------
>> 2 hints:
>> 1) A small change is needed in custom_nodetypes.xml in the test 
>> config.  Move  graffito:documentstream ahead of  
>> graffito:documentimpl in this file.
>> 2)  Get the Jackrabbit core source and put this in a third Eclipse 
>> project.    Reference this project from your jcr mapping project.   
>> This is not a requirement but it will make Eclipse's debug traces a 
>> lot easier to follow.
>> -----------------------------
>> 3 observations:
>> 1)  The object mapping itself is a pretty simple affair, maybe too 
>> simple. (Jury is still out on this.)  You must create the mapping by 
>> hand, but this is much easier than for Hibernate or JPOX mappings.   
>> However, the Graffito documentation is somewhat behind its code.    
>> For instance, you need to read the comments in the mapping DTD and 
>> look at the code to figure out inheritance mapping.   Also, it 
>> appears that for non-containment references, you need to program 
>> these references as JCR Paths.   Simple object constraints (like no 
>> dangling references), may be missing from Graffito.    JCR versioning 
>> may mitigate (or exacerbate?) the dangling ref problem.   This is 
>> still a mystery for me.
>> 2)  Jackrabbit transaction locking is still new territory for me 
>> too.   However, with or without transactions, any object updates are 
>> "very" slow.   Concurrency, too, may be limited if big chunks of 
>> content get locked during a transaction.    If you want frequent, 
>> transactional updates on objects and you want high concurrency (like 
>> optimistic locking), it may be that you need to stick with Hibernate 
>> over a RDBMS.  On the other hand, if your applications are mainly 
>> read-only (like a business reporting tool) then jcr mapping may 
>> provide much better access control than you would get using 
>> Hibernate.   (Jury is still out here, too.)
>> 3.  Multiple inheritance is a valid association of objects in a model 
>> (though Java does not support it well).      Ideally jcr mapping 
>> should deal with such a model.    It does not appear to so at this 
>> time.    With mixin types available in JCR, I had hoped for more.    
>> ("Mixin" being C++ slang for multiple inheritance.)
>>    -- Dan Connelly
>> ruchi goel wrote:
>>> Hi,
>>>   I am a  newcommer  to graffito area and  am in process of 
>>> evaluating graffito for integration with our portal server.
>>> I am mainly interested in knowing the navigation  as to how graffito 
>>> stores its java objects in JSR170 compliant repository. I understand 
>>> that graffito uses Jackrabbit. I have gone through the documentation 
>>> on graffito's web site and my understanding is that graffito is 
>>> mapping a java object to a jcr node (via mapping's file) , and then 
>>> use JSR170 on the node to talk to Jackrabbbit repository.
>>> I have downloaded the latest bits  , build, installed and deployed 
>>> on jetspeed. I use debugger to check the flow , but I am finding  
>>> that  it uses GraffitoOJBStore .
>>> *Is the jcr mapping layer not being used in the current code to talk 
>>> to JSR170 repository. ?*
>>> Though I see the code in place in the source tree : packages 
>>> org.apache.portals.graffito.jcr
>>> Help appreciated.
>>> Thanks,
>>> Ruchi

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