How can I resolve this "cannot be excluded" exception?

I am getting the following exception:

java.lang.ClassCastException: org.apache.commons.dbcp.DelegatingStatement cannot be cast to org.apache.tomcat.dbcp.dbcp.DelegatingStatement
    optimise.database.ProdigyDB.doInsertSerial(ProdigyDB.java:139)
    optimise.stock.CurrentRequest.writeRequest(CurrentRequest.java:145)
    optimise.stock.SubmitOrderServlet.processRequest(SubmitOrderServlet.java:51)
    optimise.stock.SubmitOrderServlet.doPost(SubmitOrderServlet.java:188)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    optimise.stock.AuthFilter.doFilter(AuthFilter.java:69)

      

        
        
        
      

    

The line of code is this:

 serial = ((com.informix.jdbc.IfmxStatement) ((org.apache.tomcat.dbcp.dbcp.DelegatingStatement) statement).getDelegate()).getSerial();

      

        
        
        
      

    

Full function:

public static int doInsertSerial(String sql) {
    int serial = 0;

    try {
        Connection connection = getConnection();
        java.sql.Statement statement = connection.createStatement();
        statement.executeUpdate(sql);

        serial = ((com.informix.jdbc.IfmxStatement)((org.apache.tomcat.dbcp.dbcp.DelegatingStatement) statement).getDelegate()).getSerial();

        statement.close();
        connection.close();
    } catch (SQLException e) {
        throw new RuntimeException("SQL Update Exception\n" + sql, e);                
    }

    return serial;
}

      

        
        
        
      

    

This is cryptic because the same code works fine when deployed on a Unix SCO5 server, but on a Red Hat Linux server.

Any help is greatly appreciated.

Thank.

Looking a little deeper into things, I can see that the DelegatingStatement class is showing an error:

Public class DelegatingStatement extends AbandonedTrace implements Statement {

org.apache.commons.dbcp.DelegatingStatement is not abstract and does not override the abstract isPoolable () method in java.sql.Statement

I don't understand why this is happening.