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From "David Ezzio (JIRA)" <j...@apache.org>
Subject [jira] Commented: (OPENJPA-236) No apparent way to generate all required SQL within a class derived from FullClassStrategy
Date Tue, 10 Jul 2007 19:34:04 GMT

    [ https://issues.apache.org/jira/browse/OPENJPA-236?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12511545
] 

David Ezzio commented on OPENJPA-236:
-------------------------------------

OpenJPA does not have an example of the full (or flat or vertical) class mapping where every
line of SQL used by OpenJPA is generated by user defined code.

Such an example is not easy (and probably not possible) to create because the various class
strategies are vestiges that do little in normal SQL generation. Although they provide customizing
methods to generate the SQL for some operations, the classes suffer from several shortcomings.

    1. Some SQL generation functions do not call the various class strategies and their customizing
methods. For example, lazily loading a one-to-many relationship calls only the isPrimaryKeyObjectId
method of the FullClassStrategy class and its superclasses.
        
    2. The class mappings do little in the generation of the default SQL. The real work is
done elsewhere.
        
    2. It is not clear how to implement customizing methods for a modestly complex object
model.
    
    3. It is not clear whether all required parameters are supplied to the customizing method
to handle all likely mapping situations.

    4. The level of OpenJPA skill required to be successful in customizing the generated SQL
is much higher than should be expected of our users.

There are various reasons why applications designers may want to override all (or any particular)
SQL generated by OpenJPA. For example, they may need to call stored procedures.

In addition, application developers may need to vet the generated SQL or substitute other
SQL for it. The various class mapping strategies do not provide a "here's the SQL I plan to
use, tell me what I should use" method.

A good example (and test case) of the functionality required would use a data model with table
names and column names different from the JPA defaults without any annotations or metadata
to inform OpenJPA of the differences. Instead, the user defined SQL generation would ensure
that the SQL used contained the appropriate names.

The problem involves generating the custom SQL and then, in the case of select statements,
using the result set returned.


> No apparent way to generate all required SQL within a class derived from FullClassStrategy
> ------------------------------------------------------------------------------------------
>
>                 Key: OPENJPA-236
>                 URL: https://issues.apache.org/jira/browse/OPENJPA-236
>             Project: OpenJPA
>          Issue Type: New Feature
>          Components: kernel
>    Affects Versions: 0.9.7
>            Reporter: David Ezzio
>         Attachments: OpenJPABugCustomSQL.zip
>
>
> FullClassStrategy has several optional methods for overriding OpenJPA's generation of
SQL. However, in a simple case, there is no apparent way to generate the required SQL within
a class derived from FullClassStrategy.
> The model consists of two classes, BizA which has a one-way, one-to-many relationship
to BizB. The relationship is mapped with a FK within the BizB table.
> The custom class strategy BizBMapping attempts to insert a BizB record and is able to
do so, provided that it is not contained within a BizA collection. Otherwise, the attempt
to persist a BizA with a contained BizB yields a SQL exception because OpenJPA generates additional
SQL that conflicts with the SQL generated within BizBMapping.customInsert. Even if OpenJPA
did not generate conflicting insert statement, there is no apparent way to get the value for
the A_ID column within the BizBMapping.customInsert method.
> This issue is critical for users who want to substitute their own SQL (such as calls
to stored procedures) for all of the OpenJPA generated SQL.
> Synopsis of the output log:
> INSERT INTO BIZB (ID, INFO) VALUES (?, ?) [params=(String) B22047141, (String) random]
> INSERT INTO BizA (id, info) VALUES (?, ?) [params=(String) A32968849, (String) random]
> INSERT INTO BizB (A_ID) VALUES (?) [params=(String) A32968849]
> SQLException: Column 'ID'  cannot accept a NULL value. 

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