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From "Pinaki Poddar" <ppod...@bea.com>
Subject Persistence of Service Data Objects using OpenJPA now supports Tuscany SDO DAS API
Date Wed, 01 Aug 2007 03:08:03 GMT
Hi Luciano,
  In an earlier response to your question:
  > if would be feasible to add a DAS interface[1] layer on top of Fluid
[2]?
  My answer was: Yes.

  As backup of that answer, I just added the support for SDO DAS by
implementing DASFactory/DAS/Command 
Using Fluid. These implementations are very thin-wrapper that delegates
to Fluid's JPA API.

  From a usage model, there is conceptual shift though from a SQL-based
DAS.

  Using Fluid based DAS, user code will look like: (there are some
TestCases that details it)
		DataObject person = createPerson(ssn, "Fluid", "Guy",
17);
		DAS das = getDAS();
		Command insert = das.getCommand("INSERT");
		insert.setParameter(0, person);
		insert.execute();

 to persist a Person DataObject, or to query
  		DAS das = getDAS();
		Command query = das.getCommand("SELECT");
		String jpql = "SELECT o FROM Person o WHERE
o.firstName=?1 AND o.age=?2";
		query.setParameter(0, jpql);
		query.setParameter(1, "Fluid");
		query.setParameter(2, 17);
		DataObject list = query.executeQuery();
		List result = (List)list.get(0);

Few notable points are:
  1. There is no SQL. 
  2. All object level paramaters are set via Command.setParameter()
method.
     Insert command acts on a Person DataObject (insert can be cascaded
transitively, btw) 
     which is passed to it as parameter.
  3. Query is JPQL. This is a powerful contribution of JPA. The
namespace of the query
     tokens are Object Domain tokens i.e. SDO Type and Property names;
not database
     Table or Column names. Join is navigation across a SDO DataGraph.
     OpenJPA will take care of creating the appropriate SQL. 
     User can see/monitor what SQL is being generated by OpenJPA.
  4. DAS defined return of Command.executeQuery() as a DataObject. One
would prefer it
     to be a List<DataObject> but to confirm to the API, I just return a
dynamic DataObject
     whose 0-th Property is a List<DataObject> 

And, last but not the least, applyChanges():
  		dataObject.setString("firstName", "Solid");
		das.applyChanges(dataObject); 
Will make an UPDATE to the database. 

How does user application gets a DAS?

   DASFactory dasFactory = new FluidDASFactory("SDO-DAS");
   DAS dasFactory = dasfactory.createDAS();

 1. Everything about persistence service (from database connections to
~200 configurable parameters
    supported by OpenJPA) is configured in a single file:
META-INF/persistence.xml. 
    The unit name in this file should be <persistence-unit
unitName="SDO-DAS">.
 2. The overloaded DASFactory.createDAS() that takes
org.apache.tuscany.sdo.das.rdb.Config and other
    parameters are supported simply by ignoring the argument :).  


 Regards  
 
   

  

  


Pinaki Poddar
972.834.2865

-----Original Message-----
From: Luciano Resende [mailto:luckbr1975@gmail.com] 
Sent: Friday, July 27, 2007 3:25 PM
To: tuscany-dev@ws.apache.org
Subject: Re: Persistence of Service Data Objects using OpenJPA

I haven't looked into this with any great detail, but I'd like to ask if
would be feasible to add a DAS interface[1] layer on top of Fluid [2].

Thoughts ?

[1]
https://svn.apache.org/repos/asf/incubator/tuscany/java/das/rdb/src/main
/java/org/apache/tuscany/das/rdb/DAS.java
[2] http://people.apache.org/~ppoddar/fluid/site/welcome.html

On 7/27/07, Frank Budinsky <frankb@ca.ibm.com> wrote:
> Hi Pinaki,
>
> I think your project has a lot of potential. Another related aspect is

> that there is interest in the SDO specification charter to discuss the

> possibility of converging/supporting JAXB with static SDO in version
3.
> JAXB2, as you may know, has a similar objective to support standard
POJOs.
> If that happens, then I see even more synergy with your approach. At 
> Tuscany, we'd also be very interested in the bytecode generation that 
> you mentioned you've prototyped in Fluid. Tuscany has done a little 
> bit of sandbox prototyping in that area as well, but nobody has had 
> enough time to really pursue it.
>
> Given this work, I think you should consider getting involved with the

> DAS specification effort, if you haven't already.
>
> Frank.
>
>
>
>
> "Pinaki Poddar" <ppoddar@bea.com>
> 07/27/2007 12:32 PM
> Please respond to
> tuscany-dev@ws.apache.org
>
>
> To
> <tuscany-dev@ws.apache.org>
> cc
> <dev@openjpa.apache.org>
> Subject
> Persistence of Service Data Objects using OpenJPA
>
>
>
>
>
>
> Hi Frank,
>
>    Thank you for your interest. Before I answer the specific questions

> let me say few words to explain why Fluid is attempted at first place.
>
>    A) there is a natural synergy between SDO model and the POJO model 
> where JPA excels.
>    B) Object Persistence (be it strongly-typed POJO or loosely-typed
> SDO) is complex problem by itself. Throw in quirk of multiple database

> vendors -- and one really got a hard problem in hand. OpenJPA, 
> Hibernate, TopLink had worked over many years to solve this problem to

> a reasonable degree. SDO persistence should leverage that 
> knowledge/effort instead of reinventing a costly wheel.
>
>
>  1)  Yes -- you're right. The views expressed in
>
> http://www.osoa.org/display/Main/SDO+and+Java+Persistence+Architecture
> +%
> 28JPA%29 is in agreement with what promoted me to start the lab 
> (actually I checked this page while researching and mentioned in in my

> blog). According to this wiki page: "Work on the specification of a 
> JPA data access service by the OSOA collaboration is envisaged 
> sometime in the future but has not started yet."
>    So Fluid can be considered as a prototype/exploration of similar 
> ideas.
>
>  2) Yes, I am aware of SDO's generation of Java and I have played with

> org.apache.tuscany.sdo.generate.XSD2JavaGenerator briefly.  I decided 
> to write yet another code generator for Fluid because
>
>     a) SDO2POJOGenerator handles JPA annotations as it sources SDO 
> Type information defined by XSDHelper.define().
> The annotations in the class will be made optional as we proceed -- 
> because JPA allows a separate mapping file Orm.xml thereby retaining 
> POJO-ness of the persistent domain classes.
>
>     b) The generated Java classes is "domain-ready" i.e. they are 
> self-consistent and independent. Proof: they can be compiled without 
> any other package other that java.util.*. Adding annotation, however, 
> makes them compile-dependent on jpa.jar, but that dependency will be 
> made optional as mapping information can be externalized in orm.xml.
>
>     C) as far as SDO metamodel to Java metamodel mapping goes, it is 
> essentially isomorphic (at least for this prototype).
> SDO2POJO does not introduce any extra artifact (see below). I have not

> played enough with org.apache.tuscany.sdo.generate.XSD2JavaGenerator 
> to make a fair judgement -- but most probably it is generating Java 
> classes which has more dependency on framework classes in terms of
> (inheriting/implementing) as well as package imports.
>
>    d) One mapping element is introduced in SDO-Java conversion
process.
> It is about "Container" SDO Types. I describe the details in Fluid 
> website. The reason for defining a Container Type abstraction is 
> better alignment for mapping to relational database (save extra joins 
> and allow navigational query across multi-cardinality relation paths).
>
>
>   3) Besides the source code generation route, another possibilities 
> is dynamic Java bytecode generation for SDO Types. Fluid prototyped 
> that approach too.
>
>   Regards --
>
>
> Pinaki Poddar
> 972.834.2865
>
> -----Original Message-----
> From: Frank Budinsky [mailto:frankb@ca.ibm.com]
> Sent: Friday, July 27, 2007 10:39 AM
> To: tuscany-dev@ws.apache.org
> Subject: RE: How does xsd:ID property type is distinguished from 
> xsd:string
>
> Hi Pinaki,
>
> This looks very cool, especially that you've got a working prototype! 
> I have a couple of questions.
>
> 1) This seems to overlap with the DAS plan described here:
>
>
> http://www.osoa.org/display/Main/SDO+and+Java+Persistence+Architecture
> +%
> 28JPA%29
>
> I'm not very familiar with the DAS work myself, but there seems to be 
> some overlap with your work.
>
> 2) I'm also wondering if you were aware that SDO also defines a 
> mapping to static Java interfaces/classes. See section 5 of the SDO
spec:
>
>
> http://www.osoa.org/download/attachments/36/Java-SDO-Spec-v2.1.0-FINAL
> .p
> df?version=1
>
> Does your SDO2POJOGenerator conform to that mapping? Have you tried 
> the Tuscany static SDO generator 
> (org.apache.tuscany.sdo.generate.XSD2JavaGenerator)? Is there any 
> relashionship?
>
> Frank.
>
> "Pinaki Poddar" <ppoddar@bea.com> wrote on 07/26/2007 10:41:27 PM:
>
> > Hello,
> >   I have been asking newbie questions to this forum. And people have

> > been very helpful.
> >
> >   Those newbie questions were for a Apache Lab project named Fluid 
> > -- to explore possibilities of SDO persistence using JPA API.
> >
> >   With all your help, I could put together an initial proptotype 
> > that creates/updates/queries SDO using JPA API. I used Tuscany and 
> > OpenJPA for SDO and JPA implementation respectively.
> >
> >    Further details of this project (with user documentation) can be 
> > found at
> >
> >      http://people.apache.org/~ppoddar/fluid/site/welcome.html
> >
> >    Your comments/suggestions are most welcome --
> >
> >
> > Pinaki Poddar
> > 972.834.2865
> >
> > -----Original Message-----
> > From: Frank Budinsky [mailto:frankb@ca.ibm.com]
> > Sent: Tuesday, July 24, 2007 4:59 PM
> > To: tuscany-dev@ws.apache.org
> > Subject: RE: How does xsd:ID property type is distinguished from 
> > xsd:string
> >
> > EAttribute.isID() will only be true if the type is xsd:ID.
> >
> > Frank.
> >
> > "Pinaki Poddar" <ppoddar@bea.com> wrote on 07/24/2007 05:31:09 PM:
> >
> > > Hi Frank,
> > >    > Database IDs (e.g., primary and foreign keys) are more 
> > > related to
> >
> > > xsd:key/xsd:keyref, then xsd:ID, but fortunately SDO 3 is planning

> > > to address all of them :-)
> > >
> > >   Thanks for telling me this.
> > >
> > >   Now is ((property.getType().isDataType()) &&
> > > ((EAttribute)property).isID())) == true for a property p that is 
> > > declared as xsd:key or xsd:keyref?
> > >
> > >   Or broadly, what is the semantics of Eattribute.isID()?
> > >
> > >
> > > Pinaki Poddar
> > > 972.834.2865
> > >
> > > -----Original Message-----
> > > From: Frank Budinsky [mailto:frankb@ca.ibm.com]
> > > Sent: Tuesday, July 24, 2007 3:01 PM
> > > To: tuscany-dev@ws.apache.org
> > > Subject: RE: How does xsd:ID property type is distinguished from 
> > > xsd:string
> > >
> > > Hi Pinaki,
> > >
> > > Identity support is also in the SDO 3 charter: Support for a 
> > > concept
>
> > > of identity in SDO, and its relationship to other technologies.
> > >
> > > Database IDs (e.g., primary and foreign keys) are more related to 
> > > xsd:key/xsd:keyref, then xsd:ID, but fortunately SDO 3 is planning

> > > to address all of them :-)
> > >
> > > Frank.
> > >
> > > "Pinaki Poddar" <ppoddar@bea.com> wrote on 07/24/2007 11:02:21 AM:
> > >
> > > > Hi Frank,
> > > >   Thanks.
> > > >
> > > > > SDO (SDO 3) is planning to provide an api for accessing 
> > > > > extended
>
> > > > > XSD
> > > > metadata
> > > >
> > > >   That is good news. However, identity mechanics should appear 
> > > > more distinctly on API surface e.g.
> > > >    boolean Proprty.isIdentifier();
> > > >    List<Property> Type.getIdentifiers();
> > > >
> > > > I will qualify absence of any identity semantics from SDO a 
> > > > major drawback. Especially, if it comes to any persistence 
> > > > operation on SDO DataObject/DataGraph. Hopefully some of the SDO

> > > > spec writers would notice this omission and add it to future
spec version.
> > > >
> > > > After a quick pick in current DAS implementation, it appeared 
> > > > that
>
> > > > 'primary key' identification is based on existing database 
> > > > column name
> > >
> > > > "ID" (yes, hardcoded) -- but I may be wrong and am ready to 
> > > > learn how DAS is handling identity issue.
> > > >
> > > > > SDO (SDO 3) is planning to provide an api for accessing 
> > > > > extended
>
> > > > > XSD
> > > > metadata
> > > > That is a good decision. Wrapping should always provide access 
> > > > to what
> > >
> > > > is being wrapped.
> > > >
> > > > > downcasting to the EMF implementation class
> > > >
> > > > Thanks for this info. I will do this for now. But I heed your 
> > > > advice
> >
> > > > and have already a scheme in place that programs against *only* 
> > > > commonj.sdo API but can access underlying implementaion, if 
> > > > available,
> > >
> > > > without any compile-time binding.
> > > > Slightly costly -- but works for, say, extracting package name 
> > > > from Types.
> > > >
> > > >
> > > >
> > > > Pinaki Poddar
> > > > 972.834.2865
> > > >
> > > > -----Original Message-----
> > > > From: Frank Budinsky [mailto:frankb@ca.ibm.com]
> > > > Sent: Tuesday, July 24, 2007 9:16 AM
> > > > To: tuscany-dev@ws.apache.org
> > > > Subject: Re: How does xsd:ID property type is distinguished from

> > > > xsd:string
> > > >
> > > > Hi Pinaki,
> > > >
> > > > They can't be distinguished in the current version of SDO 
> > > > metadata, you need to look at the original XSD. The next version

> > > > of SDO (SDO
> > > > 3) is planning to provide an api for accessing extended XSD 
> > > > metadata. In Tuscany, you can currently determine this by 
> > > > downcasting to the EMF implementation class, although we don't
> > recommend people do that:
> > > >
> > > >       System.out.println("  Property isID: " +
> > > > ((property.getType().isDataType()) && 
> > > > ((EAttribute)property).isID()));
> > > >
> > > > Frank.
> > > >
> > > > "Pinaki Poddar" <ppoddar@bea.com> wrote on 07/24/2007 01:00:03
AM:
> > > >
> > > > >
> > > > > Hi,
> > > > >
> > > > > A newbie question:
> > > > >    How does two Property: one defined as xsd:string and other 
> > > > > as
>
> > > > > xsd:ID can be distiguished?
> > > > >
> > > > > Assume:
> > > > >  1. we have a simple XML schema defining a Person SDO Type 
> > > > > with two properties as follows:
> > > > >     <xsd:complexType name="Person">
> > > > >          <xsd:attribute name="firstName" type="xsd:string"/>
> > > > >          <xsd:attribute name="id"        type="xsd:ID"/>
> > > > >     </xsd:complexType>
> > > > >
> > > > >  2. TypeHelper.INSTANCE.define()
> > > > >     defines SDO Type with two commonj.sdo.Property, p1 (for
> > > > > firstName)
> > > >
> > > > > and p2 (for id)
> > > > >
> > > > >  3. both p1.getType().getInstanceClass() and
> > > > > p2.getType().getInstanceClass() return java.lang.String
> > > > >     both p1.getType().isDataType() and 
> > > > > p2.getType().isDataType()
>
> > > > > return true
> > > > >
> > > > > The question is, what can be done to identify p2 as a property

> > > > > that were defined as xsd:ID?
> > > > >
> > > > >
> > > > > Thanks for your help --
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > Pinaki Poddar
> > > > > 972.834.2865
> > > > >
> > > > > Notice:  This email message, together with any attachments, 
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--
Luciano Resende
Apache Tuscany Committer
http://people.apache.org/~lresende
http://lresende.blogspot.com/

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