......
  <script type="text/javascript" src="../js/taconite-client.js"></script>
  <script type="text/javascript" src="../js/taconite-parser.js"></script>
  <script language="javascript">
    //选择产品分类
    function selectCatalog(vproductCatalog) {
        if (vproductCatalog.value == "") {
          hint("请先选择产品分类");
        } else {
          hint("加载中...");
          var ajaxRequest = new AjaxRequest("<html:rewrite page="/product/queryProductsAction.do"/>");
          ajaxRequest.setQueryString("catalogId=" + vproductCatalog.value);
          ajaxRequest.sendRequest();
        }
    }
    function hint(msg) {
        var e = document.getElementById("PTypeSelectList");
        while (e.childNodes.length > 0) {
          e.removeChild(e.childNodes[0]);
        }
        var option = document.createElement("option");
        var text = document.createTextNode(msg);
        option.appendChild(text);
        e.appendChild(option);
    }
  </script>
......
<table width="600" border="1" cellpadding="0" cellspacing="0" bordercolor="#E7E7E7">
          <tr>
            <td bgcolor="#F6F6F6" class="t_1">　产品分类目录
            <html:select property="productCatalog" onchange="selectCatalog(this)">
            <html:option value ="">请选择产品分类</html:option>
            <html:options collection ="productCatalogs" property="value" labelProperty="label"/>
            </html:select>
            </td>
          </tr>
          <tr>
            <td align="left" class="t_1">　产品类型目录
            <html:select property="productType" styleId="PTypeSelectList">
            <html:option value ="">请先选择产品分类</html:option>
            <html:options collection ="productTypes" property="value" labelProperty="label"/>
            </html:select>
            <html:submit property="query" value="查 询"/></td>
          </tr>
          </table>
          </html:form>

<%@ page contentType="text/html; charset=UTF-8" %>
<%@ taglib uri="/WEB-INF/struts-bean.tld" prefix="bean" %>
<%@ taglib uri="/WEB-INF/struts-html.tld" prefix="html" %>
<%@ taglib uri="/WEB-INF/struts-logic.tld" prefix="logic" %>
<%@ taglib uri="[url]http://java.sun.com/jstl/core[/url]" prefix="c" %>
<%@ taglib uri="/WEB-INF/struts-nested.tld" prefix="nested" %>
<%@ taglib uri="[url]http://taconite.sf.net/tags[/url]" prefix="tac" %>
<tac:taconiteRoot>
<tac:replaceChildren contextNodeID="PTypeSelectList" parseOnServer="false">
      <option value="" >请选择产品类型</option>
  <nested:iterate id="view" name="productTypes" >
      <option value="<nested:write name="view" property="value" />" ><nested:write name="view" property="label" /></option>
  </nested:iterate>
</tac:replaceChildren>
</tac:taconiteRoot>

public class QueryProductsAction extends Action {
  public ActionForward execute(ActionMapping mapping,ActionForm form,HttpServletRequest request,HttpServletResponse response) {
    ......
    UtilBusiness utilBusiness = new UtilBusinessImpl();
    request.setAttribute("productCatalogs",utilBusiness.getAllProductCatalogs());
    int catalogId = 0;
    if(request.getParameter("catalogId") != null && request.getParameter("catalogId").length != 0){
        catalogId = Integer.parseInt(request.getParameter("catalogId"));
    }
    request.setAttribute("productTypes",utilBusiness.getAllPTypes(catalogId));
    return mapping.findForward("showPType");
    ......
  }
}

public List getAllPTypes(int catalogId) throws DaoException{
    String getAllProductTypes = "select id,name from productType where catalogId = ?";      
    Connection con = null;
    PreparedStatement ps = null;
    ResultSet rs = null;
    try {
        List list = new ArrayList();
        PType pType;
        con = super.getConnection();
        ps = con.prepareStatement(getAllProductTypes);
        ps.setInt(1,catalogId);
        rs = ps.executeQuery();
        while (rs.next()) {
          pType = new PType();
          pType.setLabel(rs.getString("name"));
          pType.setValue(String.valueOf(rs.getInt("id"));
          list.add(pType);
        }
        return list;
    } catch (SQLException sqle) {
        sqle.printStackTrace();
    } catch (NullPointerException npe) {
        npe.printStackTrace();
    } finally {
          if (null != rs) {
            rs.close();
          }
          if (null != ps) {
            ps.close();
          }
          if (null != con) {
            con.close();
          }  
}