[jira] [Reopened] (DERBY-4944) Embedded Derby does not start when derby.jar is dynamically uploaded / added to the classpath

["Myrna van Lunteren (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/DERBY-4944?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Myrna van Lunteren reopened DERBY-4944:
---------------------------------------
      Assignee: Myrna van Lunteren  (was: Dag H. Wanvik)

reopening for backport to 10.7 as requested.

> Embedded Derby does not start when derby.jar is dynamically uploaded / added to the classpath
> ---------------------------------------------------------------------------------------------
>
>                 Key: DERBY-4944
>                 URL: https://issues.apache.org/jira/browse/DERBY-4944
>             Project: Derby
>          Issue Type: Bug
>          Components: Store
>    Affects Versions: 10.6.2.1
>         Environment: various windows versions, jdk1.6.0 and 1.5.0
>            Reporter: Michael Dobrovnik
>            Assignee: Myrna van Lunteren
>            Priority: Minor
>             Fix For: 10.8.1.2
>
>         Attachments: BDFF.diff
>
>
> Hi, 
> For our workflow-system, we can use a variety of DBMS as the store engine. Derby is one of them especially popular
> for test and development purposes. During setup of our system, we allow to upload a jar file with the JDBC-Driver for the DBMS.
> In case of derby, we use the embedded mode and upload derby.jar. After that we add the jar to the repositories of our class loader
> and call 
> Class drc = Class.forName("org.apache.derby.jdbc.EmbeddedDriver", true, ourclassloader);
> Driver drv = (Driver)drc.newInstance();
> this worked perfectly for many years up to version 10.6.1.0, but ceased to work in 10.6.2.1; 
> i assume the unreleased future versions are affected, too
> when derby.jar is placed in the classpath manually before starting our setup, everything works fine regardless of the derby version.
> investigations lead to the following conclusion:
> - since rev. 982370 this is broken, in the immediate predecessor rev. 980035  it worked.
> - rev. 982370 in  the org.apache.derby.impl.store.raw.data.BaseDataFileFactory class introduced a new method
>     private static String jarClassPath(final Class cls) which tries to find the jarfile from which derby was loaded.
>   it contains the following lines: 
> if ( cs == null )
>   return null;
> URL result = cs.getLocation();
> return result.toString();        
>   but in the case, when we dynamically load derby, 
>   cs is not null but cs.getLocation() is null. so i propose to change the line with the if to:
> ...
> if ( cs == null || cs.getLocation()==null)
>   return null;
> ...
> or maybe it would be better to surround the whole body of the method with a try catch, since it is not essential, and a null 
> return value is also ok?
> thank you for your efforts concerning derby at large, 
> Michael



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