ajax與json

1.jquery中調用ajax方法

$.ajax({
  async:true,
  type:"post",
  url:"xxxServlet",
  data:{"account":"jack","pwd":"123"},
  success:function(data){
      //dowork
  },
  //error:function(){alert("error!");},
  dataType:"json"
});
注:指定dataType爲json時,不要用var obj = eval("("+data+")");去再次解析,會報錯

2.json格式

1.json對象
  {key:value,key:value}
  {"name":"jack","sex":"男","age":"25"}
2.json數組或集合格式
  [{key:value,key:value},{key:value,key:value}]
  [{"name":"jack","sex":"男","age":"25"},     {"name":"tom","sex":"男","age":"26"}]
3.json對象,數組嵌套
  {  
        "param":[{key:value,key:value},{key:value,key:value}] 
  }
  {
    "param1":[{key:value,key:value},{key:value,key:value}],
    "param2":[{key:value,key:value},{key:value,key:value}],
    "param3":[{key:value,key:value},{key:value,key:value}]
  }
  {
     "param1":"value1",
     "param2":{},
     "param3":[{key:value,key:value},{key:value,key:value}]
  }

3.谷歌的gson包

Gson gson = new Gson();
  String json = gson.toJson(car);
  resp.getWriter().write(json);

4.阿里的fastjson包

JSON-jsonString(toJOSNString) 
JSONObject-map集合(put) 
JSONArray-list集合(add)

4.1.響應jsonString

String jsonString = JSON.toJSONString(car);
resp.getWriter().write(jsonString);

4.2.響應json對象

JSONObject data=JSONObject.parseObject(JSON.toJSONString(car));
resp.getWriter().print(data);

4.3.JSONObject對象

JSONObject jo = new JSONObject();
jo.put("message", "用戶名可註冊!");
resp.getWriter().print(jo);

4.4.JSONArray數組

JSONObject jo1 = new JSONObject();
JSONObject jo2 = new JSONObject();
JSONArray ja = new JSONArray();
ja.add(jo1);
ja.add(jo2);
resp.getWriter().println(ja);