code: public Object javaToSql(Object source) throws ConversionException
      {
  
          if (source == null)
          {
              return NULLVALUE;
          }
  
          try
          {
              List stringList = (List) source;
              if (stringList.isEmpty())
              {
                  return NULLVALUE;
              }
  
              StringBuffer result = new StringBuffer();
              for (int i = 0; i < stringList.size(); i++)
              {
                  String newSt = (String) stringList.get(i);
                  // introduced in JDK 1.4, replace with commons-lang
                  // newSt = newSt.replaceAll("#", "##");
                  newSt = StringUtils.replace(newSt, "#", "##");
                  if (i > 0)
                  {
                      result.append("#");
                  }
                  result.append(newSt);
              }
              return result.toString();
          }
          catch (ClassCastException e)
          {
              throw new ConversionException("Object is not a List of String it is a"
                      + source.getClass().getName());
          }
      }
docs: /* (non-Javadoc)
  @see org.apache.ojb.broker.accesslayer.conversions.FieldConversion#javaToSql(java.lang.Object)