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From "Patrick Linskey" <>
Subject RE: Using query hints for mapping extensions in orm.xml
Date Tue, 16 Jan 2007 01:12:32 GMT

It kinda feels like we're corrupting the intended use of query hints.
Plus, it seems unfortunate to have to drop back into untyped strings if
we can avoid it.

I think that there is another approach that we've talked about earlier:
use namespaces to intersperse OpenJPA data into the orm.xml file. That's
my preferred solution.


Patrick Linskey
BEA Systems, Inc. 

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> -----Original Message-----
> From: Marc Prud'hommeaux [] On 
> Behalf Of Marc Prud'hommeaux
> Sent: Monday, January 15, 2007 12:26 PM
> To:
> Subject: Using query hints for mapping extensions in orm.xml
> OpenJPA people-
> A limitation of the JPA specification is that there is no built-in  
> way to put implementation-specific extensions in an orm.xml file,  
> which limits the use of OpenJPA's many useful extensions to only  
> being expressible annotations. Past suggestions for getting around  
> this limitation have been to alter the locally-cached version of the  
> XSD (which would make any orm.xml file that takes advantage of this  
> non-portable) or to have an additional file that contains the  
> extensions (e.g., an "openjpa-orm.xml" file peered with the 
> "orm.xml"  
> file).
> It just occurred to me that there is another possibility: the "hint"  
> child of the "named-query" element is a free-form field that acts as  
> a means to pass a query hint to the implementation. We could expand  
> on this to allow the passing of a mapping hint to the implementation  
> via a special-cased "openjpa.extensions.EntityName" named query in  
> which we could embed hints for the entity and its attributes. 
> See the  
> example below for how it might work.
> What do people think? It would allow us to keep the 
> extensions in the  
> same file in which the rest of the mappings are expressed, but still  
> remain portable to other JPA implementations (since other  
> implementations are supposed to ignore unrecognized query hints).
> <?xml version="1.0" encoding="UTF-8"?>
> <entity-mappings xmlns=""  
> version="1.0">
>      <package>org.apache.openjpa.mappingextensions</package>
>      <entity name="Department" class="Department">
>          <table name="DEPARTMENT"/>
>          <!-- OpenJPA mapping extensions for the Department entity -->
>          <named-query name="openjpa.extensions.Department">
>              <!-- empty query element, since it is required -->
>              <query/>
>              <!-- class-level hints -->
>              <hint name="" value="false"/>
>              <!-- hints for the "employees" field -->
>              <hint name="openjpa.employees.jdbc-eager-fetch-mode"  
> value="parallel"/>
>              <hint name="openjpa.employees.jdbc-nonpolymorphic"  
> value="true"/>
>          </named-query>
>          <!-- standard mappings follow -->
>          <attributes>
>              <id name="id">
>                  <column name="ID"/>
>              </id>
>              <basic name="name">
>                  <column name="NAME"/>
>              </basic>
>              <one-to-many name="employees" fetch="EAGER">
>                  <join-column name="FK_EMPS"/>
>              </one-to-many>
>          </attributes>
>      </entity>
> </entity-mappings>

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