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From "Cefn Hoile (JIRA)" <j...@apache.org>
Subject [jira] Created: (OPENJPA-1896) OpenJPA cannot store POJOs if a corresponding record already exists
Date Tue, 23 Nov 2010 16:34:13 GMT
OpenJPA cannot store POJOs if a corresponding record already exists
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                 Key: OPENJPA-1896
                 URL: https://issues.apache.org/jira/browse/OPENJPA-1896
             Project: OpenJPA
          Issue Type: Bug
    Affects Versions: 2.0.1
         Environment: Eclipse, Sun Java 1.6, Ubuntu Lucid, Guice JPAPersistModule, build-time
enhance.xml
            Reporter: Cefn Hoile


If a POJO is created using a java constructor, merge() cannot store the newly constructed
object's data if this means updating a pre-existing record with a matching identity.

This is a major bug since it means applications where the objects have a natural key cannot
use OpenJPA. In my case the example was a filesystem; each crawl of the filesystem generates
its own data objects with file path as the natural key. These objects then need to be stored
into the database. Previous crawls may have encountered the same files, and the merge operation
should cause the latest data from the POJO to be stored in the pre-existing record.

Instead, any attempt to execute either merge() or persist() on an independently constructed
object with a matching record identity in the database triggers the same error in the database
layer, since OpenJPA attempts to execute an insert for a pre-existing primary key, throwing...
org.apache.openjpa.lib.jdbc.ReportingSQLException: ERROR: duplicate key value violates unique
constraint "file_pkey" {prepstmnt 32879825 INSERT INTO file (locationString, location, version,
folder) VALUES (?, ?, ?, ?)  [params=?, ?, ?, ?]} [code=0, state=23505]

>From discussion with Rick Curtis on the users@openjpa.apache.org list, this is because
the version field on a POJO which is unmanaged is not yet set. 

An ASSUMPTION seems to be made that no such record exists in the database already since it
wasn't loaded from the database in the first place, so a persist is attempted. Instead, I
recommend the database is QUERIED TO FIND OUT if such a record already exists, and the version
field is set correspondingly before attempting the merge() 

Here is the corresponding thread containing Ricks comments and links to an example in Github
which can recreate the problem.
http://mail-archives.apache.org/mod_mbox/openjpa-users/201011.mbox/%3CAANLkTi=tzs-nB6+NQQJmUcfbpCF_kzPnhOtLkYHvH+bM@mail.gmail.com%3E

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