public class CategoryAction extends ActionSupport {
    private List<Category> subcates;
    //。。。。省略get/set方法
    public String getsubcates(){
    subcates=categoryManger.getSubCates(pid);
    return SUCCESS; [color=#FF0000]//注意此处[/color]
    }
 }

     <package name="json"  extends="json-default" >
        <action name="getsubcatesaction" class="categoryAction" method="getsubcates">
            <result name="success" type="json">
                <param name="includeProperties">
                    subcates\[\d+\]\.id,subcates\[\d+\]\.name
                </param>
            </result>
        </action>
    </package>

        function addsubcotes(pid){ 
            alert(pid);
            ajaxUtil("getsubcatesaction.action?pid="+pid,false,true,null,true,
                function(data){
                    alert(data); 
                    var jsonObject = eval('(' + data + ')');
                    var select = document.getElementById("subcate");
                    select.options.length=0;//清空select
                    alert(jsonObject.subcates);
                    for(var i = 0;i<jsonObject.subcates.length;i++){
                        var category = list.subcates[i];
                        slect.add(new Option(category.name,category.id));
                    }
                }
            );
        }