json基础

json表示法是一种轻量级的基于文本的开放标准

json是javascript object notation的缩写

json的网络媒体格式是 application/json

容易阅读和编写

语言无关性

json的几种数据格式

对象

An object is an unordered set of name/value pairs. An object begins with { (left brace) and ends with } (right brace). Each name is followed by : (colon) and the name/value pairs are separated by .

object

数组

An array is an ordered collection of values. An array begins with [ (left bracket) and ends with ] (right bracket). Values are separated by ,

array

值

A value can be a string in double quotes, or a number, or true or false or null, or an object or an array. These structures can be nested.

value

json语法

数据使用键值对表示

使用大括号表示对象，每个名称后面跟着一个:，键值对之间使用,分割

使用方括号[]保存数组，数组值使用,分割

{

"book": [

{

"id":"01",

"language": "Java",

"edition": "third",

"author": "Herbert Schildt"

},

{

"id":"07",

"language": "C++",

"edition": "second"

"author": "E.Balagurusamy"

}]

}

book为键，它对应的又是一个json数组对象,json数组用[]包起来：

[

{

"id":"01",

"language": "Java",

"edition": "third",

"author": "Herbert Schildt"

},

{

"id":"07",

"language": "C++",

"edition": "second"

"author": "E.Balagurusamy"

}

]

数组元素是一个json对象，对象之间使用,隔开：

{

"id":"01",

"language": "Java",

"edition": "third",

"author": "Herbert Schildt"

}

java中使用json

下载 json .jar

/**

* 测试生成json对象

* @throws JSONException

*/

@Test

public void testBuildJsonObject() throws JSONException {

JSONObject jsonObject = new JSONObject();

jsonObject.put("id",1);

jsonObject.put("name","shixu");

jsonObject.put("age",23);

jsonObject.put("id",2); //JsonObject底层是维护一个map,所以不能有重复的键,这里会把之前的值覆盖掉

System.out.println(jsonObject);

System.out.println("id:"+jsonObject.get("id"));

System.out.println("name:"+jsonObject.get("name"));

System.out.println("age:"+jsonObject.get("age"));

HashMap map = new HashMap<>();

map.put("id",1);

map.put("name","shixu");

JSONObject jsonObjectMap= new JSONObject(map); //使用map初始化

System.out.println(jsonObjectMap);

System.out.println("id:"+jsonObjectMap.get("id"));

System.out.println("name:"+jsonObjectMap.get("name"));

}

结果：

{"id":2,"age":23,"name":"shixu"}

id:2

name:shixu

age:23

{"id":1,"name":"shixu"}

id:1

/**

* 测试生成JSONArray ,用于存放jsonObject

* @throws JSONException

*/

@Test

public void testBuildJsonArray() throws JSONException {

JSONArray jsonArray = new JSONArray();

HashMap map = new HashMap<>();

map.put("id",1);

map.put("name","shixu");

JSONObject jsonObjectMap= new JSONObject(map); //使用map初始化

jsonArray.put(jsonObjectMap);

jsonArray.put(jsonObjectMap);

System.out.println(jsonArray);

System.out.println(jsonArray.getJSONObject(0));

System.out.println(jsonArray.getJSONObject(1));

}

结果：

[{"id":1,"name":"shixu"},{"id":1,"name":"shixu"}]

{"id":1,"name":"shixu"}

{"id":1,"name":"shixu"}

将一个json字符串解析为json对象

/**

* 将一个json字符串解析为json对象

* @throws JSONException

*/

@Test

public void testJsonStrToJsonObject() throws JSONException {

String jsonStr = "[{\"id\":1,\"name\":\"shixu\"},{\"id\":2,\"name\":\"suntime\"}]";

JSONTokener jsonTokener = new JSONTokener(jsonStr);

JSONArray jsonArray = new JSONArray(jsonTokener);

for (int i = 0; i

JSONObject jsonObject = jsonArray.getJSONObject(i);

System.out.println(jsonObject);

System.out.print("id:"+jsonObject.get("id"));

System.out.println("\tname:"+jsonObject.get("name"));

}

}

结果：

{"id":1,"name":"shixu"}

id:1 name:shixu

{"id":2,"name":"suntime"}

id:2 name:suntime

总结