[
http://issues.apache.org/jira/browse/DERBY-668?page=comments#action_12359101 ]
Daniel John Debrunner commented on DERBY-668:
---------------------------------------------
Is this code used?
+ // Given a loaded class, and the name by which we loaded that class, this
+ // routine asks the class's class loader for information about where the
+ // class was loaded from. Typically, this is a file, which might be
+ // either a class file or a jar file. The routine figures that out, and
+ // returns the name of the file. If it can't figure it out, it returns null
+ private static String getFileWhichLoadedClass(Class c, String cName)
+ {
+ String className = "/" + cName.replace('.', '/') + ".class";
+ java.net.URL url = c.getResource(className);
because I thought a class loader was not allowed to return the .class file as a
resource for security reasons.
> 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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