使用gson获取json对象

以下是一个省市级联的的例子：

文本框里的内容：

<select class="text" name="district_id"
           onchange="getStreet(this.value);">
           <option value="-1">
            请选择所属区
           </option>
           <c:forEach var="districName"
            items="${requestScope.districList}">
            <option value="${districName.id}">
             ${districName.name}
            </option>
           </c:forEach>
          </select>
          街：
          <select class="text" name="street_id" id="street">
           <option>
            请选择街道
           </option>
          </select>

js里：

 <script type="text/javascript">
  function getStreet(districtId){
    var url = "getStreet2.action";
   var postData = {districtId:districtId};
   $.getJSON(url,postData,function(data){
    $("#street").empty();
    $.each(data,function(i){
     var item = data[i];
     var option = $("<option value='"+item.districtId+"'>"+item.name+"</option>");
     $("#street").append(option);
    });
   });
  }
 </script>

action里：

 Gson gson=new Gson();
  String json=gson.toJson(obj);
  response.setCharacterEncoding("utf-8");
  try {
   response.getWriter().write(json);
  } catch (IOException e) {
   e.printStackTrace();
  }