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From "Rick Hillegas (JIRA)" <derby-...@db.apache.org>
Subject [jira] Commented: (DERBY-930) Add support for autoloading of Derby client drivers
Date Mon, 19 Jun 2006 15:04:30 GMT
    [ http://issues.apache.org/jira/browse/DERBY-930?page=comments#action_12416775 ] 

Rick Hillegas commented on DERBY-930:

Adding a release note for this issue:


If an embedded Derby application generates its own Derby properties on the fly, and that Derby
application runs in the same VM with other JDBC applications, then you are not guaranteed
that the Derby engine will pick up the custom properties when it boots.


Derby startup behavior will be non-deterministic. Sometimes the engine will pick up the custom
properties and sometimes it won't.


JDBC4 introduced driver-autoloading. This causes all JDBC drivers visible to the VM to register
themselves the first time some application requests a Connection. When the embedded Derby
driver registers itself, it also boots the Derby engine and the engine picks up whatever Derby
properties are currently visible. An embedded Derby application may want to configure the
engine properties before asking for a Connection. That embedded Derby application will not
get a chance to configure engine properties if some other JDBC application in the same VM
runs first and requests a Connection. Two related bugs describe this issue in greater detail:
DERBY-1428 and DERBY-1429.


There is no general solution to the problem. If two self-configuring embedded Derby applications
run in the same VM, then only one of them can win.


The following workarounds may be useful:

1) Don't configure Derby properties inside your applications. Instead, specify Derby properties
either on the VM startup line or in a $DERBY_HOME/derby.properties which remains constant
for the VM's lifetime.

2) If (1) is not possible, then make the self-configuring Derby application run first.

> Add support for autoloading of Derby client drivers
> ---------------------------------------------------
>          Key: DERBY-930
>          URL: http://issues.apache.org/jira/browse/DERBY-930
>      Project: Derby
>         Type: New Feature

>   Components: Build tools, JDBC
>     Reporter: Rick Hillegas
>     Assignee: Rick Hillegas
>      Fix For:
>  Attachments: ClassloadingTest.jar, bug930.diff, bug930_problem.diff, bug930_problem2.diff,
bug930_rev2.diff, bug930_rev3.diff
> Write Derby's driver names into the correct spot in derby.jar and derbyclient.jar so
that the 1.6 vm autoloads Derby drivers. Section 10.2.1 of the JDBC4 spec describes the details.

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