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From "Andrew McIntyre (JIRA)" <derby-...@db.apache.org>
Subject [jira] Commented: (DERBY-668) SysInfo can give misleading information when JDBC jars are loaded from jre/lib/ext
Date Fri, 02 Dec 2005 00:32:31 GMT
    [ http://issues.apache.org/jira/browse/DERBY-668?page=comments#action_12359106 ] 

Andrew McIntyre commented on DERBY-668:
---------------------------------------

Class.getResource() doesn't return the .class file itself, it returns the URL of the location
from which the class in question has already been loaded. This is used to determine the actual
location of the loaded class, whether it was loaded by the extensions mechanism or from the
classpath.

Because we're just asking for the location of the file, I don't believe there are any security
manager issues. If we tried to load the class from the URL, that might be a problem if we
don't have sufficient permissions to access the class.

> 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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