Embedded Derby does not start when derby.jar is dynamically uploaded / added to
the classpath
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Key: DERBY-4944
URL: https://issues.apache.org/jira/browse/DERBY-4944
Project: Derby
Issue Type: Bug
Components: Store
Affects Versions: 11.0.0.0
Environment: various windows versions, jdk1.6.0 and 1.5.0
Reporter: Michael Dobrovnik
Priority: Minor
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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