Knight of the round table

1.      從以下網址http://code.google.com/p/jsonplugin/downloads/list下載JSON插件的JAR包（新版本是0.32），并加到工程的相應目錄下。從如下網址http://docs.jquery.com/Downloading_jQuery下載jquery所需文件。(建議下載穩定版本，不然會出現莫名其妙的錯誤)
2.      配置相應的xml文件，為ajax請求提供數據：
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
    "http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
    <package name="sajax" extends="json-default" namespace="/book">
        <action name="getAjaxBookChannelList" method="getAjaxBookChannelList" class="bookChannelAction">
            <result type="json" />
        </action>
        <action name="getAjaxBookCategoryListByChannelID" method="getAjaxBookCategoryListByChannelID" class="bookChannelAction">
            <result type="json" />
        </action>
    </package>
</struts>
配置有兩處與通常的action配置不同，一處是擴展了json-default， json-default”是在jsonplugin-0.30.jar包里的struts-plugin.xml中定義的，文件內容如下：
<?xml version="1.0" encoding="UTF-8" ?>

<!DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
    "http://struts.apache.org/dtds/struts-2.0.dtd">

<struts>
    <package name="json-default" extends="struts-default">
        <result-types>
            <result-type name="json" class="com.googlecode.jsonplugin.JSONResult"/>
        </result-types>
        <interceptors>
            <interceptor name="json" class="com.googlecode.jsonplugin.JSONInterceptor"/>
        </interceptors>
    </package>
</struts>

另一處是定義了返回類型為json<result type="json" />，會將response中的返回數據轉化為json對象。
3．在Action中的定義。定義返回對象，并添加get，set方法。返回的數據可以根據需要格式成json形式(json格式如{1:test,2:test})，比如為二級列表提供填充內容的的數據，在頁面需要進行遍歷，做成json形式的，在頁面遍歷時也會比較方便。Action代碼（部分）如下：
   
    public String getAjaxBookChannelList() {
       StringBuffer sb = new StringBuffer();
       bookChannelList = bookService.getBookChannelList();
       if (bookChannelList.size() > 0) {
           int j = bookChannelList.size();
           sb.append("{");
           for (int i = 0; i < j; i++) {
              BookChannel bc = (BookChannel) bookChannelList.get(i);
              sb.append(bc.getId());
              sb.append(":");
              sb.append("\"");
              sb.append(bc.getName());
              sb.append("\"");
              if (i != (j - 1))
                  sb.append(",");
           }
           sb.append("}");
       }

       strAjaxChannel = sb.toString();//返回的數據

       return Action.SUCCESS;
    }


4頁面操作。Jquery中已經提供幾供ajax請求的方法，如果返回的是json對象，使用jQuery.getJSON(url,[data],[callback])會比較方便，

jQuery.getJSON(url,[data],[callback]) 通過 HTTP GET 請求載入 JSON 數據。

返回值
XMLHttpRequest

參數
url (String) : 發送請求地址。
data (Map) : (可選) 待發送 Key/value 參數。
callback (Function) : (可選) 載入成功時回調函數。

參數部分，瀏覽器的緩存是以url為標識的，如果url相同會使用緩存中的數據，如果不想使用緩存，可以在參數中加入一個隨機數。

jQuery.each(obj,callback)
通用例遍方法，可用于例遍對象和數組
參數
object (Object) : 需要例遍的對象或數組。
callback (Function) : (可選) 每個成員/元素執行的回調函數。
回調函數擁有兩個參數：第一個為對象的成員或數組的索引，第二個為對應變量或內容。
Jquery操作下拉列表添加選項的方法為: $(“# categoryId”)[0].options.add(option);

頁面代碼如下（部分）：
<. language="." type="text/." src="/.s/jquery-1.2.2.js"></.>
<. language=".">
       function fillChannel(id){
              var url = "/book/getAjaxBookChannelList.action";
              $.getJSON(url,{ran:Math.random()},function(json){
                     if(json.strAjaxChannel.length > 0){
                            var obj = .('(' + json.strAjaxChannel + ')');
                            $.each(obj,function(i,n){
                          option = new Option(n,i);
                          if(i==id)option.selected=true;
                         document.getElementById("channellistId").options.add(option);
                      });
                      option = new Option("全部頻道",999);
                      if(id == 999)option.selected=true;
                      document.getElementById("channellistId").options.add(option); 
                  }
               else{
                           option = new Option("暫無頻道");
                           document.getElementById("channellistId").options.add(option);
                  }
                     }
              );    
       }
       function fillCategory(chid,bid){
              document.getElementById("categoryId").options.length=1;
              var url = "/book/getAjaxBookCategoryListByChannelID.action";
              var cid = 0;
              if(chid > 0){
                     cid = chid;
              }
              else{
                     cid = document.getElementById("channellistId").value;
              }
              $.getJSON(url,{channelID:cid,ran:Math.random()}, function(json){
        //參數為頻道ID及隨機數，function(json)為回調函數，其中json為取到的返回數據
                       if(json.strAjaxCategory.length > 0){
                                   var obj = .('(' + json.strAjaxCategory + ')');//將json文本轉化為json對象，以便于遍歷
                                   $.each(obj,function(i,n){  //jquery中的遍歷方法，
                                 option = new Option(n,i);
                                 if(i==bid)option.selected=true;
                                document.getElementById("categoryId").options.add(option);
                             });
                                  option = new Option("全部分類","-3");
                                  if(bid ==-3)option.selected=true;
                                  document.getElementById("categoryId").options.add(option);
                                  //jquery的方法為:$(“# categoryId”)[0].options.add(option);
                  }
                  else{
                           if(cid == 999){
                                  option = new Option("全部分類","-1");
                                  document.getElementById("categoryId").options.add(option);                              
                           }
                           else{
                                  option = new Option("暫無分類");
                                  document.getElementById("categoryId").options.add(option);
                           }
                  }
                     }
              );           
       }

       function fillSelect(chid,cid){
              fillChannel(chid);
              fillCategory(chid,cid);
       }
</.>
<body <s:if test="bookCategory.bookchannelId >0">onLoad="fillSelect(<s:property value="bookCategory.bookchannelId"/>,<s:property value="bookCategory.id"/>);"</s:if><s:if test="bookCategory==null">onLoad="fillChannel(0);"</s:if>>

作品類別
         <select name="channellistId" id="channellistId" onChange="fillCategory(<s:if test="bookCategory.bookchannelId >0">0,</s:if><s:property value="categoryId"/>);"><option>選擇頻道</option></select>
         <select name="categoryId" id="categoryId"><option>選擇分類</option></select>


直接訪問http://manager.17k.com/book/getAjaxBookChannelList.action
得到如下內容：
{"ajaxBookCategoryListByChannelID":"success","ajaxBookChannelList":"success","bcID":0,"bchID":0,"bookCategory":null,"bookCategoryAllList":null,"bookCategoryByChannelID":"success","bookCategoryByID":null,"bookCategoryList":null,"bookCategoryListModel":null,"bookChannel":null,"bookChannelList":[{"createdate":"2008-07-09T10:23:36","id":1,"name":"暢銷經典","prefix":"changxiao","status":0},{"createdate":"2008-07-09T10:24:03","id":2,"name":"玄幻奇幻","prefix":"yy","status":0},{"createdate":"2008-07-09T10:24:25","id":3,"name":"都市娛樂","prefix":"dushi","status":0},{"createdate":"2008-07-09T10:24:38","id":4,"name":"歷史軍事","prefix":"ss","status":0},{"createdate":"2008-07-09T10:24:54","id":5,"name":"女性時尚","prefix":"nvxing","status":0},{"createdate":"2008-07-09T10:25:11","id":6,"name":"游戲競技","prefix":"dongman","status":0},{"createdate":"2008-07-09T10:25:24","id":7,"name":"恐怖靈異","prefix":"kongbu","status":0},{"createdate":"2008-07-09T10:25:35","id":8,"name":"文化社科","prefix":"www","status":0},{"createdate":"2008-07-09T10:25:46","id":9,"name":"經管勵志","prefix":"www","status":0}],"channelID":0,"currentPage":0,"info":"","msg":"","pageSize":0,"srcID":0,"strAjax":"","strAjaxCategory":"","strAjaxChannel":"{1:\"暢銷經典\",2:\"玄幻奇幻\",3:\"都市娛樂\",4:\"歷史軍事\",5:\"女性時尚\",6:\"游戲競技\",7:\"恐怖靈異\",8:\"文化社科\",9:\"經管勵志\"}","tarID":0,"theBookCategory":"success","theBookChannel":"success","toID":0}




關于jsonplugin序列化的幾點：
a.對于不想被序列化的屬性，可以在他的get方法前加注釋：      @JSON(serialize=false)
b.對于想改變json結果屬性名稱的，可以在他的get方法前加注釋@JSON(name="屬性名")
c. 帶有transient修飾符與沒有Getter方法的字段（field）都不會被串行化為JSON。