[z]struts2 json jquery 集成详解

1.      从以下网址 http://code.google.com/p/jsonplugin/downloads/list 下载JSON插件的JAR包（新版本是0.32），并加到工程的相应目录下。从如下网址 http://docs.jquery.com/Downloading_jQuery 下载jquery所需文件。(建议下载稳定版本，不然会出现莫名其妙的错误) 
2.      配置相应的xml文件，为ajax请求提供数据： 
<?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> 
配置有两处与通常的action配置不同，一处是扩展了json-default， json-default”是在jsonplugin-0.30.jar包里的struts-plugin.xml中定义的，文件内容如下： 
<?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> 

另一处是定义了返回类型为json<result type="json" />，会将response中的返回数据转化为json对象。 
3．在Action中的定义。定义返回对象，并添加get，set方法。返回的数据可以根据需要格式成json形式(json格式如{1:test,2:test})，比如为二级列表提供填充内容的的数据，在页面需要进行遍历，做成json形式的，在页面遍历时也会比较方便。Action代码（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();//返回的数据 

       return Action.SUCCESS; 
    } 


4页面操作。Jquery中已经提供几供ajax请求的方法，如果返回的是json对象，使用jQuery.getJSON(url,[data],[callback])会比较方便， 

jQuery.getJSON(url,[data],[callback]) 通过 HTTP GET 请求载入 JSON 数据。 

返回值 
XMLHttpRequest 

参数 
url (String) : 发送请求地址。 
data (Map) : (可选) 待发送 Key/value 参数。 
callback (Function) : (可选) 载入成功时回调函数。 

参数部分，浏览器的缓存是以url为标识的，如果url相同会使用缓存中的数据，如果不想使用缓存，可以在参数中加入一个随机数。 

jQuery.each(obj,callback) 
通用例遍方法，可用于例遍对象和数组 
参数 
object (Object) : 需要例遍的对象或数组。 
callback (Function) : (可选) 每个成员/元素执行的回调函数。 
回调函数拥有两个参数：第一个为对象的成员或数组的索引，第二个为对应变量或内容。 
Jquery操作下拉列表添加选项的方法为: $(“# categoryId”)[0].options.add(option); 

页面代码如下（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("全部频道",999); 
                      if(id == 999)option.selected=true; 
                      document.getElementById("channellistId").options.add(option);  
                  } 
               else{ 
                           option = new Option("暂无频道"); 
                           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){ 
        //参数为频道ID及随机数，function(json)为回调函数，其中json为取到的返回数据 
                       if(json.strAjaxCategory.length > 0){ 
                                   var obj = .('(' + json.strAjaxCategory + ')');//将json文本转化为json对象，以便于遍历 
                                   $.each(obj,function(i,n){  //jquery中的遍历方法， 
                                 option = new Option(n,i); 
                                 if(i==bid)option.selected=true; 
                                document.getElementById("categoryId").options.add(option); 
                             }); 
                                  option = new Option("全部分类","-3"); 
                                  if(bid ==-3)option.selected=true; 
                                  document.getElementById("categoryId").options.add(option); 
                                  //jquery的方法为:$(“# categoryId”)[0].options.add(option); 
                  } 
                  else{ 
                           if(cid == 999){ 
                                  option = new Option("全部分类","-1"); 
                                  document.getElementById("categoryId").options.add(option);                               
                           } 
                           else{ 
                                  option = new Option("暂无分类"); 
                                  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>> 

作品类别 
         <select name="channellistId" id="channellistId" onChange="fillCategory(<s:if test="bookCategory.bookchannelId >0">0,</s:if><s:property value="categoryId"/>);"><option>选择频道</option></select> 
         <select name="categoryId" id="categoryId"><option>选择分类</option></select> 


直接访问 http://manager.17k.com/book/getAjaxBookChannelList.action 
得到如下内容： 
{"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":"畅销经典","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":"都市娱乐","prefix":"dushi","status":0},{"createdate":"2008-07-09T10:24:38","id":4,"name":"历史军事","prefix":"ss","status":0},{"createdate":"2008-07-09T10:24:54","id":5,"name":"女性时尚","prefix":"nvxing","status":0},{"createdate":"2008-07-09T10:25:11","id":6,"name":"游戏竞技","prefix":"dongman","status":0},{"createdate":"2008-07-09T10:25:24","id":7,"name":"恐怖灵异","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":"经管励志","prefix":"www","status":0}],"channelID":0,"currentPage":0,"info":"","msg":"","pageSize":0,"srcID":0,"strAjax":"","strAjaxCategory":"","strAjaxChannel":"{1:\"畅销经典\",2:\"玄幻奇幻\",3:\"都市娱乐\",4:\"历史军事\",5:\"女性时尚\",6:\"游戏竞技\",7:\"恐怖灵异\",8:\"文化社科\",9:\"经管励志\"}","tarID":0,"theBookCategory":"success","theBookChannel":"success","toID":0} 




关于jsonplugin序列化的几点： 
a.对于不想被序列化的属性，可以在他的get方法前加注释：      @JSON(serialize=false) 
b.对于想改变json结果属性名称的，可以在他的get方法前加注释@JSON(name="属性名") 
c. 带有transient修饰符与没有Getter方法的字段（field）都不会被串行化为JSON。