Ajax

1. 底层步骤
   实例对象
   创建HTTP请求
   发送请求
   设置回调函数
2. 使用jQuery

$.ajax({ 
    "url":"/AjaxDemoServlet",
    "type":"POST", 
    "data":"name="+name+"&pwd="+pwd, 
    "dataType":"JSON", 
    "success":callBack,
    "error":function () {
        alert("验证时出现错误！");
    }
});
function callBack(data) {
    ...
}

$.post({url,data,callBack,dataType};
function callBack(data) {
    ...
}

$(selector).load(url[,data][,complete]);//加载HTML内容

3. JSON

var person={"name":"Mary","age":25,"spouse":null};
var nation=["中国","美国","俄罗斯"];
var p=[{"name":"Mary","age":25},{"name":"Bob","age":27}];

//将普通对象转换为JSON对象
先导入jar包
String newsJSON=JSON.toJSONString();