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Date: Fri, 2 Dec 2005 01:40:33 +0100 (CET)
From: "Daniel John Debrunner (JIRA)" <derby-dev@db.apache.org>
To: derby-dev@db.apache.org
Subject: [jira] Commented: (DERBY-668) SysInfo can give misleading information
 when JDBC jars are loaded from jre/lib/ext
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    [ http://issues.apache.org/jira/browse/DERBY-668?page=comments#action_12359108 ] 

Daniel John Debrunner commented on DERBY-668:
---------------------------------------------

The comment for ClassLoader.getResource says:

a URL for reading the resource, or null if the resource could not be found or the caller doesn't have adequate privileges to get the resource.

Thus if you don't have permission to read the class you should get null back.

Not sure how this affects this patch, I know in the class loader that loads from the database I implemented to return null for any request for a file ending in .class, I'd just assumed most class loaders did that.

> SysInfo can give misleading information when JDBC jars are loaded from jre/lib/ext
> ----------------------------------------------------------------------------------
>
>          Key: DERBY-668
>          URL: http://issues.apache.org/jira/browse/DERBY-668
>      Project: Derby
>         Type: Bug
>   Components: Build tools
>     Versions: 10.1.1.0
>     Reporter: Bryan Pendleton
>     Priority: Minor
>  Attachments: Derby-668.diff, derby-668-2.diff, derby-668-3.diff
>
> There is a section in the SysInfo tool's output titled "Derby Information", which prints location and version information for the major Derby jars. Here is an example of that output:
> --------- Derby Information --------
> JRE - JDBC: J2SE 1.4.2 - JDBC 3.0
> [/home/bpendleton/src/derby-subversion/trunk/jars/insane/derby.jar] 10.2.0.0 alpha - (315052M)
> [/home/bpendleton/src/derby-subversion/trunk/jars/insane/derbytools.jar] 10.2.0.0 alpha - (315052M)
> [/home/bpendleton/src/derby-subversion/trunk/jars/insane/derbynet.jar] 10.2.0.0 alpha - (315052M)
> [/home/bpendleton/src/derby-subversion/trunk/jars/insane/derbyclient.jar] 10.2.0.0 alpha - (315052M)
> [/home/bpendleton/downloads/derby/db2jcc/lib/db2jcc.jar] 2.4 - (17)
> [/home/bpendleton/downloads/derby/db2jcc/lib/db2jcc_license_c.jar] 2.4 - (17)
> Unfortunately, this tool can be fooled if you arrange for one of these jar files to be loaded from a magic location like $JAVA_HOME/jre/lib/ext.
> For example, I had (accidentally) placed an old version of db2jcc.jar into $JAVA_HOME/jre/lib/ext. When I ran SysInfo, it printed out: 
> --------- Derby Information --------
> JRE - JDBC: J2SE 1.4.2 - JDBC 3.0
> [/home/bpendleton/src/derby-subversion/trunk/jars/insane/derby.jar] 10.2.0.0 alpha - (315052M)
> [/home/bpendleton/src/derby-subversion/trunk/jars/insane/derbytools.jar] 10.2.0.0 alpha - (315052M)
> [/home/bpendleton/src/derby-subversion/trunk/jars/insane/derbynet.jar] 10.2.0.0 alpha - (315052M)
> [/home/bpendleton/src/derby-subversion/trunk/jars/insane/derbyclient.jar] 10.2.0.0 alpha - (315052M)
> [/home/bpendleton/downloads/derby/db2jcc/lib/db2jcc.jar] 1.0 - (581)
> [/home/bpendleton/downloads/derby/db2jcc/lib/db2jcc_license_c.jar] 1.0 - (581)
> However, the "1.0 (581)" information actually came from $JAVA_HOME/jre/lib/ext/db2jcc.jar, NOT from
> /home/bpendleton/downloads/derby/db2jcc/lib/db2jcc.jar.
> It would be nice if SysInfo could detect the difference between a jar file being loaded via the application class loader using $CLASSPATH, and a jar file being loaded via the system class loader using JDK library extensions.
> To reproduce the problem, simply:
> 1) Place an older version of db2jcc.jar into $JAVA_HOME/jre/lib/ext
> 2) Place a newer version of db2jcc.jar into your $CLASSPATH
> 3) Run SysInfo. You will see that it prints the name of the jarfile from $CLASSPATH, but the version info from the JDK copy.

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