String columnName = request.getParameter("columnName");
String keyColumnName = request.getParameter("keyColumnName");
String separator = request.getParameter("separator");
AbstractOperation op = new MultiValuedCellJoinOperation(columnName, keyColumnName, separator);
Process process = op.createProcess(project, new Properties());
performProcessAndRespond(request, response, project, process);
} catch (Exception e) {
respondException(response, e);
}