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Ajax——json

2016-03-15 15:50 423 查看

json是js提供的一种数据交换格式！

json的语法

* {}：是对象！

> 属性名必须使用双引号括起来！单引不行！！！

> 属性值：

* null

* 数值

* 字符串

* 数组：使用[]括起来

* boolean值：true和false

应用json

var person = {"name":"zhangSan", "age":18, "sex":"male"};

json与xml比较

* 可读性：XML胜出

* 解析难度：JSON本身就是JS对象（主场作战），所以简单很多

* 流行度：XML已经流行好多年，但在AJAX领域，JSON更受欢迎。

package servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.junit.Test;

public class AServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

response.setContentType("text/html;charset=utf-8");
String str="{\"name\":\"Zhangsan\",\"age\":16,\"sex\":\"male\"}";
response.getWriter().print(str);
System.out.println(str);
}

}

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">

<title>My JSP 'json1.jsp' starting page</title>

<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
<script type="text/javascript">
function createXMLHttpRequest(){
try {
return new XMLHttpRequest();
} catch (e) {
try {
return new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
try {
return new ActiveXObject("MicroSoft.XMLHTTP");
} catch (e) {
// TODO: handle exception
}
}
}
}
window.onload=function(){
var bt=document.getElementById("bt");
bt.onclick=function(){
var xmlHttp=createXMLHttpRequest();
xmlHttp.open("GET","<c:url value='/AServlet' />",true);
xmlHttp.send(null);
xmlHttp.onreadystatechange=function(){
if(xmlHttp.readyState==4 && xmlHttp.status==200){
var text=xmlHttp.responseText;
var person=eval("("+text+")");
var s=person.name+","+person.age+","+person.sex;
document.getElementById("h1").innerHTML=s;
}
};
};
};
</script>
</head>

<body>
<h1>json演示</h1>
<button id="bt">点击这里</button>
<h1 id="h1"></h1>
</body>
</html>

json-lib可以把javabean转换成json串

核心类

* JSONObject --> Map

> toString();

> JSONObject map = JSONObject.fromObject(person)：把对象转换成JSONObject对象

* JSONArray --> List

> toString()

> JSONArray jsonArray = JSONObject.fromObject(list)：把list转换成JSONArray对象

package demo;

import java.util.ArrayList;
import java.util.List;

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;

import org.junit.Test;

public class Demo {
@Test
public void fun1(){
JSONObject map=new JSONObject();
map.put("name", "ZHangsan");
map.put("age", 16);
map.put("sex", "male");
String s = map.toString();
System.out.println(s);

}
@Test
public void fun2() {
Person p=new Person("Lisi",18,"male");
//把对象转换成JSONObject对象
JSONObject map=JSONObject.fromObject(p);
String s = map.toString();
System.out.println(s);
}
@Test
public void fun3() {
Person p1=new Person("Lisi",55,"male");
Person p2=new Person("haha",33,"male");

JSONArray list=new JSONArray();
list.add(p1);
list.add(p2);
String s = list.toString();
System.out.println(s);
}

@Test
public void fun4() {
Person p1=new Person("Lisi",55,"male");
Person p2=new Person("haha",33,"male");
List<Person> list=new ArrayList<Person>();
list.add(p1);
list.add(p2);

System.out.println(JSONArray.fromObject(list));
}

}

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