[jira] Commented: (OPENJPA-1610) Allow applications using OpenJPA 1.x to run with the JPA 2.0 jar on the classpath

["David Ezzio (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/OPENJPA-1610?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12881850#action_12881850 ] 

David Ezzio commented on OPENJPA-1610:
--------------------------------------

In the OpenJPA 1.1.x branch, when the PersistenceProductDerivation attempted to
parse a persistence.xml with the version attribute of the persistence element
set to 2.0, it threw a SAXParseException. This led to a spurious error message
that stymied users when the application is actually attempting to use another
persistence provider.

The solution is similar to the strategy used in JPA 2.0 to parse either JPA 1 or
JPA 2 compliant documents. A trivial, non-validating parser preparses the
document to determine the version. If the version is 2.0, then a warning is
issued, and the PersistenceProductDerivation load method returns a null
ConfigurationProvider. This in turns causes the PersistenceProviderImpl's create
EMF methods to adhere to their contracts of returning null when they are unable
to provide the required service.


> Allow applications using OpenJPA 1.x to run with the JPA 2.0 jar on the classpath
> ---------------------------------------------------------------------------------
>
>                 Key: OPENJPA-1610
>                 URL: https://issues.apache.org/jira/browse/OPENJPA-1610
>             Project: OpenJPA
>          Issue Type: Improvement
>          Components: jpa
>    Affects Versions: 1.1.1
>            Reporter: David Ezzio
>            Assignee: David Ezzio
>             Fix For: 1.1.1
>
>         Attachments: Patch930357n378.diff
>
>
> OpenJPA 1.x does not support JPA 2.0, but there are runtime environments
> where applications using OpenJPA 1.x must run with the JPA 2.0 jar
> present in the classpath.
> Although JPA 2.0 is upwardly compatible with JPA 1.0, JPA 2.0 introduced
> some methods to existing JPA interfaces that conflict with existing
> signatures in OpenJPA interfaces.  These conflicts arise because
> the OpenJPA interfaces extend the JPA interfaces that picked up the new 
> methods.
> To avoid the linkage errors that would result from no changes to
> OpenJPA, when applications using the offending methods run in such an
> environment, the two offending methods should be changed in the OpenJPA
> interfaces.
> Applications deployed in such environments should be recompiled to avoid
> any possibility of using the old methods.
> The offending methods are 
>     public <T> T OpenJPAEntityManager.detach(T pc)
>     public Properties OpenJPAEntityManagerFactory.getProperties()
>     
> The proposed fixes are designed to make recompilation and correction of
> such applications as simple as possible. Such applications will compile
> with either the JPA 2.0 or JPA 1.0 jar, but they should be compiled with
> the JPA 1.0 jar to avoid mistakenly using interfaces or methods found
> only in JPA 2.0. Any such coding mistakes will result in linkage errors
> when the methods or interfaces are used at runtime.
> The proposed fixes:
>     public <T> T OpenJPAEntityManager.detachCopy(T pc)
>     public Map<String, Object) OpenJPAEntityManagerFactory.getProperties()
>     
>     public Properties OpenJPAEntityManagerFactory.getPropertiesAsProperties()
>     
> The first two fixes follow the changes made in OpenJPA 2.x to address
> these same conflicts.
> The getPropertiesAsProperties method is provided as a convenience to
> application developers who do not want to accept the different return
> type of the redesigned getProperties method. However, the method
> getPropertiesAsProperties is not currently found in the OpenJPA 2.x
> interface.
> It is estimated that a large proportion of OpenJPA 1.x enabled
> applications are using the old detach method and that a small proportion
> are using the old getProperties method.

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