json

概念

javascript object notation js标示对象的一种方式

作用

1、标示数据，键值对形式 2、保存数据 3、json可以作为数据交换的格式

特点

轻量级，原生js

json对象 本质就是js代码 var aa={"name":"lisu"}
json数据 字符串
eval();

json数据

map形式

1、key/value

{"name":"zhangsan","age":"30"};

2、object

{"stu":{"name":"lisi","age":"21"}}

3、array

{"tea":[
        {"name":"lisi","age":"21"},
        {"name":"zhangsan","age":"22"}
    ]
}

4、复杂嵌套

{
    "stu2":[
        {"sex":0,"username":"lisi"},{"sex":0,"username":"zhaoliu"},
        {"password":"123","sex":0,"username":"zhangsan"}
    ],
    "stu1":{"password":"123","sex":1,"username":"zhangsan"}
}

list形式

[
    {"name":"lisi","age":"21"},
    {"name":"zhangsan","age":"22"}
]

[
    [
        {"name":"lisi","age":"21"},
        {"name":"zhangsan","age":"22"}
    ],
    [
        {"name":"lisi","age":"21"},
        {"name":"zhangsan","age":"22"}
    ]
]

json工具类

访问官网http://www.json.org/
找到java平台的json工具类，例如json-java
到github下载源码
导入到eclipse，导出jar

json-java的使用

javabean对象转成json对象

User user=new User("zhaoliu", "123");
JSONObject json=new JSONObject(user);//将user对象转成json对象

list对象转成json对象

User user1=new User("lisi","123");
User user2=new User("zhaoliu","123");
User user3=new User("zhangsan","123");

List list=new ArrayList();
list.add(user1);
list.add(user2);
list.add(user3);

JSONArray json=new JSONArray(list);//将list转成json对象