Use Java functions with Apache Derby -

i've encountered problems using functions in apache derby, in can't derby find self-defined functions. typical error message looks this:

the class 'de.uniba.kinf.projm.hylleblomst.database.sql.utils.groupconcat' not exist or inaccessible.  can happen if class not public. 

the documentation states method must public , static. want use:

package de.uniba.kinf.projm.hylleblomst.database.sql.utils; public final class groupconcat {     public static string groupconcat(string separator, string... arguments) {         stringbuilder result = new stringbuilder("");         (string arg : arguments) {             result.append(arg + separator + " ");         }         result.delete(result.length() - 2, result.length());         return result.tostring();     } } 

basically want add groupconcat functionality database not provided in derby standard. statement use add function db this:

create function sql_util.group_concat      ( separator char, args varchar(255) ... )     returns varchar(2000)     parameter style derby     no sql language java     external name 'de.uniba.kinf.projm.hylleblomst.database.sql.utils.groupconcat.groupconcat' 

i've packed groupconcat class in jar , added classpath derby should able find , added database directly. here's did: .jar lies in lib-folder of project, part of build path (i'm using eclipse). entry in classpath-file of project looks this:

<classpathentry kind="lib" path="lib/groupconcat.jar"/> 

and measure , desperation i've added system's classpath:

. ; ..;%derby_home%\lib\derby.jar;%derby_home%\lib\derbytools.jar;c:\users\workspace\kinf-workspace\general\lib 

my error trivial, i'm quite new derby , databases in general, i'd appreciate help.

thanks in advance!

the problem turned out more specific eclipse , in nature trivial. although jar containing java-class in classpath, eclipse did not add jar run configurations. apparently, classpath passed on derby there , of course can't find class. there packing class containing method in question jar, adding project's library, add run configuration's classpath , run it.

lessons learned: never trust ide (all of) work.