Re: [tcljava-user] Class not found after successful class import.]

[Patrick F. <pfi...@oz...>]

Thanks for the tip Mo.  The class is loaded but I now get an SQL error.

"set c [ java::field ClientDriver class ]"

This loads the class but the subsequent call to "DriverManager" generates 
a "no suitable driver sql error".


I am trying to emulate the JDBC load database driver using the Class 
forName technique explained here:
http://www.jguru.com/faq/view.jsp?EID=11164

Class.forName("org.apache.derby.jdbc.EmbeddedDriver");
Connection conn = DriverManager.getConnection( "jdbc:derby:mynewDB", p);

In JACL the method call fails with a class not found error.

"java::call Class forName org.apache.derby.jdbc.ClientDriver"
"set ConnectionI [ java::call DriverManager getConnection $url ]"

I had another look at the Class API and added the tcl class loader as 
the loader
parameter.

set c [ java::field ClientDriver class ]
set classLoader [ $c getClassLoader ]

In this case the classloader is " tcl.lang.TclClassLoader" because the 
jar file containing "ClientDriver" is specified using the tcl_classpath 
variable.

"java::call Class forName org.apache.derby.jdbc.ClientDriver true 
$classLoader"

Class.forName now loads ClientDriver but I still get 
"java.sql.SQLException: No suitable driver" on the call to DriveManager.

It does look like a classloader issue. The work around is to add the
Derby database jar files to the system classpath.

set CLASSPATH=%CLASSPATH%;C:\IBM\Cloudscape_10.1\lib\derby.jar
set CLASSPATH=%CLASSPATH%;C:\IBM\Cloudscape_10.1\lib\derbyclient.jar
set CLASSPATH=%CLASSPATH%;C:\IBM\Cloudscape_10.1\lib\derbynet.jar
set CLASSPATH=%CLASSPATH%;C:\IBM\Cloudscape_10.1\lib\derbytools.jar

c:\tclblendSun\bin\jtclsh.bat 
C:\CvsSandbox\FITZROY\FM\SCRIPTS\TCL\JACL\cloudscape\createCloudScapeDB.tcl

When the foloowng statements are executed...................

set c [ java::field ClientDriver class ]
set  classLoader [ $c getClassLoader ] 


the classloader for ClientDriver is now 
"sun.misc.Launcher$AppClassLoader" and the call to DriveManager succeeds.

So it would seem that the process that the database driver class uses to 
register the driver with the DriveManager only works if it's loaded with 
the same class loader as the DriveManager.

"The specified driver must implement the Driver interface. A class 
initializer (static code block) within the OracleDriver class registers 
the driver with the DriverManager". 
 
Regards.

Patrick.