JFreeChart com JSP e BD MySQL

public ArrayList select() throws SQLException {
      //abre uma conexão
      ...
      PreparedStatement ps = conn.prepareStatement("SELECT valor FROM tabela");
      ResultSet rs = ps.executeQuery();
      ArrayList array = new ArrayList();
      while(rs.netx()) {
         array.add(new Double(rs.getDouble("valor"))); // estou supondo que sua tabela tem um double
      }
      rs.close();
      ps.close();
      conn.close();
      return array;
   }

...
   ArrayList results = DAO.select();
   DefaultCategoryDataSet dataset = new DefaultCategoryDataSet();
   for(Iterator it = results.iterator(); it.hasNext();) {
      Double valor = (Double) it.next();
      dataset.addValue(valor.doubleValue(), "idColuna", "idLinha");
   }