[Mondrian] xmla over olap4j server

Julian Hyde jhyde at pentaho.com
Tue Apr 19 00:20:01 EDT 2011

I have checked in your changes as change 14208. I moved things around a bit
-- I moved your olap4j connection factory out of XmlaServlet into a new
derived class, Olap4jXmlaServlet. And the previous functionality, to start
an embedded mondrian server, is in a new subclass MondrianXmlaServlet.
I hope that I have preserved the intent of your changes.
Thanks for the contribution. It definitely moves us down the road to an XMLA
server that is independent of mondrian.
Other users (including Pentaho BI server team), take note: Applications that
used DefaultXmlaServlet should probably now use MondrianXmlaServlet.


From: Michele Rossi [mailto:michele.rossi at gmail.com] 
Sent: Friday, April 15, 2011 1:36 AM
To: Mondrian developer mailing list
Cc: jhyde at pentaho.com
Subject: Re: [Mondrian] xmla over olap4j server

[ re sending to the whole list as requested by Julian ]

Hi Julian, 
I've completed the first stage of the xmla-over-olap4j work.

I still haven't found out how to create patch files - it can probably be
done using the p4 client, I will look at it tomorrow.

For now I am attaching to this email the three files that I updated and an
example web.xml that shows how the servlet could be deployed.
You can find most of my changes easily by searching for [MROSSI].

Initially I tried to split out the servlet from the rest of the Mondrian
codebase but the dependencies are many and go fairly deep.
I am not sure that such an endeavour would be very valuable.
After all there is nothing wrong in just using the whole mondrian jar as it

I've tested my code using Excel and the SimbaO2X adapter.
I can successfully connect to a Foodmart olap database in the following way:

Excel-->Simba-->My Server with the modified DefaultXmlaServlet-->Olap4j Xmla
Driver-->A standard mondrian installation with a standard xmla servlet.

I will need to make some more changes to handle the credentials passed by
Excel in the XMLA requests.
I did most of the work last year but never contributed it back.

What do you think?
How do you think I should proceed from this point?

Many thanks!

On 11 March 2011 17:56, Julian Hyde <jhyde at pentaho.com> wrote:



From: Michele Rossi [mailto:michele.rossi at gmail.com] 
Sent: Friday, March 11, 2011 1:43 AM
To: mondrian at pentaho.org; jhyde at pentaho.com
Subject: Re: [Mondrian] xmla over olap4j server

[re-sending from my private email address as it's not working from my work

I have a few questions for you:

1. How do I get started?
Can you create an account on perforce for me with write permissions? 

Please submit your changes as patches attached to jira cases. We don't give
people committer privileges until they have made a few successful

 2. Olap4j drillthrough
The mondrian olap4j driver implements drillthrough via the "executeQuery"
method which returns a java.sql.ResultSet right? 
Can we not leverage that method to implement drillthrough on the xmla

Possibly. Depends on your requirements. Mondrian's XMLA clients expect more
in the XMLA response than is currently available in the ResultSet returned
by that method. Therefore the XMLA server calls a method in XmlaExtra. The
default implementation of XmlaExtra calls executeQuery. Same effect, longer


3. The new project:
We will need a new "olap4j xmla server" project with its separate build an
Can you think of a good name for it?
Perhaps Olap4jXmlaServer could be a good candidate :) 

Sounds reasonable.

4. How to build the new project: 
I know that mondrian is built using Ant.

Have you ever thought about starting to use Maven?
I've used Maven successfully for years and I've totally forgot how to use

I think it would also be beneficial in terms of linking olap4j releases with
server releases.
We could then distribute both olap4j, mondrian and the xmla server on public
maven repositories. 

At this point I don't want to create a new project. I would like to work
with the xmla server code in situ in the mondrian code base, to learn what
the necessary changes are, and where would be the appropriate cut points.
Then I will help you factor it into another project. But first, let's get it
working in situ.
Re. maven, see below.

5. Proposed solution
I can put together a webapp project quickly using the following ingredients 

a. maven build

b. unit tests based on mondrian: 
You create an in-process mondrian instance and connect to it using the
mondrian olap4j driver. 
Then you hit the new server using the olap4j xmla driver. 
You can then compare results making assertions on the equality of metadata
and values.

c. The output artifact would a standard .WAR file 

d. Jetty launcher
I propose the creation of a jetty launcher too. 
I can create such launcher using maven reasonably quickly. 
The result would be a tar.gz file with a number of sub-folders, one of them
containing the .war file discussed above, others containing shared jetty
libraries and finally the .bat and .sh launchers.

We could then have a "cfg" folder with a template .properties file where a
user would have to put the details of his/her favourite olap4j driver and
the connection details. 

All of the above sounds fine. In due course. But please, don't make big
changes as the first step. (I've found that the most successful committers
are the ones who submit small patches at first.)
In this case, the patches would be whatever hacks to mondrian's xmla server
are necessary to build your flavor of the server. I will learn a lot from
those patches.
When time comes to create the new project, we can discuss using maven. You'd
have to make a strong case, because it would be a Pentaho project
(containing about 15k of mondrian source code, plus unit tests) and Pentaho
projects have standardized on using an ant+ivy+subfloor infrastructure.


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