json语法和json解析
2019-05-15 本文已影响42人
测试老杨
json介绍
json是一种数据结构，任何东西都可以使用json格式的数据来表示。
image.png
json格式的天气预报数据如下：
{
"time": "2019-05-16 11:17:51",
"cityInfo": {
"city": "上海市",
"cityId": "101020100",
"parent": "上海",
"updateTime": "10:48"
},
"date": "20190516",
"message": "Success !",
"status": 200,
"data": {
"shidu": "93%",
"pm25": 41,
"pm10": 42,
"quality": "良",
"wendu": "19",
"ganmao": "极少数敏感人群应减少户外活动",
"yesterday": {
"date": "15",
"sunrise": "05:00",
"high": "高温 22.0℃",
"low": "低温 18.0℃",
"sunset": "18:42",
"aqi": 35,
"ymd": "2019-05-15",
"week": "星期三",
"fx": "东南风",
"fl": "<3级",
"type": "小雨",
"notice": "雨虽小，注意保暖别感冒"
},
"forecast": [
{
"date": "16",
"sunrise": "04:59",
"high": "高温 24.0℃",
"low": "低温 19.0℃",
"sunset": "18:43",
"aqi": 50,
"ymd": "2019-05-16",
"week": "星期四",
"fx": "东风",
"fl": "3-4级",
"type": "小雨",
"notice": "雨虽小，注意保暖别感冒"
},
{
"date": "17",
"sunrise": "04:58",
"high": "高温 26.0℃",
"low": "低温 20.0℃",
"sunset": "18:43",
"aqi": 48,
"ymd": "2019-05-17",
"week": "星期五",
"fx": "东南风",
"fl": "3-4级",
"type": "小雨",
"notice": "雨虽小，注意保暖别感冒"
},
{
"date": "18",
"sunrise": "04:58",
"high": "高温 27.0℃",
"low": "低温 18.0℃",
"sunset": "18:44",
"aqi": 72,
"ymd": "2019-05-18",
"week": "星期六",
"fx": "西北风",
"fl": "3-4级",
"type": "多云",
"notice": "阴晴之间，谨防紫外线侵扰"
},
{
"date": "19",
"sunrise": "04:57",
"high": "高温 26.0℃",
"low": "低温 18.0℃",
"sunset": "18:45",
"aqi": 62,
"ymd": "2019-05-19",
"week": "星期日",
"fx": "南风",
"fl": "<3级",
"type": "小雨",
"notice": "雨虽小，注意保暖别感冒"
},
{
"date": "20",
"sunrise": "04:57",
"high": "高温 25.0℃",
"low": "低温 17.0℃",
"sunset": "18:45",
"aqi": 44,
"ymd": "2019-05-20",
"week": "星期一",
"fx": "北风",
"fl": "4-5级",
"type": "多云",
"notice": "阴晴之间，谨防紫外线侵扰"
},
{
"date": "21",
"sunrise": "04:56",
"high": "高温 26.0℃",
"low": "低温 18.0℃",
"sunset": "18:46",
"aqi": 58,
"ymd": "2019-05-21",
"week": "星期二",
"fx": "南风",
"fl": "<3级",
"type": "晴",
"notice": "愿你拥有比阳光明媚的心情"
},
{
"date": "22",
"sunrise": "04:55",
"high": "高温 28.0℃",
"low": "低温 17.0℃",
"sunset": "18:47",
"ymd": "2019-05-22",
"week": "星期三",
"fx": "南风",
"fl": "<3级",
"type": "多云",
"notice": "阴晴之间，谨防紫外线侵扰"
}
]
}
}
json语法
1、表示对象的话，使用{开始，使用}结束，比如：
{"empno":1001,"ename":"张三","isMale":true,"hiredate":1557978889881}
2、表示数组的话，使用[开始，使用]结束，比如：
[{"empno":1001,"ename":"张三","isMale":true},{"empno":1002,"ename":"李四"}]
3、特殊字符的含义
1）[ 表示数组的开始
2）] 表示数组的结束
3）{ 表示对象的开始
4）} 表示对象的结束
5）" 定义属性名，以及用来表示字符串类型的数据
6）: 连接属性名和属性值
7）, 分隔符（属性之间使用该符号分隔，元素之间使用该符号分隔）
4、怎么判断是对象还是数组
1）如果json串是以 { 开始，以 } 结束的话，则表示对象
2）如果json串是以 [ 开始，以 ] 结束的话，则表示数组
5、json支持嵌套
1）对象里面可以嵌套对象，比如：
{"empno":1003,"ename":"王五","dept":{"dno":10,"dname":"研发","loc":"上海"}}
2）数组里面可以嵌套对象，比如：
[{"empno":1001,"ename":"张三","isMale":true},{"empno":1002,"ename":"李四"}]
3）对象里面可以嵌套数组
{"code":200,"data":[{"empno":1001,"ename":"张三"},{"empno":1002,"ename":"李四"}]}
fastjson介绍
1、什么是fastjson?
fastjson是阿里巴巴的开源JSON解析库，它可以解析JSON格式的字符串，支持将Java Bean序列化为JSON字符串，也可以从JSON字符串反序列化到JavaBean。
2、fastjson的优点
1）速度快
fastjson相对其他JSON库的特点是快，从2011年fastjson发布1.1.x版本之后，其性能从未被其他Java实现的JSON库超越。
2）使用广泛
fastjson在阿里巴巴大规模使用，在数万台服务器上部署，fastjson在业界被广泛接受。在2012年被开源中国评选为最受欢迎的国产开源软件之一。
3）测试完备
fastjson有非常多的testcase，在1.2.11版本中，testcase超过3321个。每次发布都会进行回归测试，保证质量稳定。
4）使用简单
fastjson的API十分简洁。
String text = JSON.toJSONString(obj); //序列化
VO vo = JSON.parseObject("{...}", VO.class); //反序列化
5）功能完备
支持泛型，支持流处理超大文本，支持枚举，支持序列化和反序列化扩展。
将json格式的字符串转成json数组（json对象的数组）
json串内容的格式如下：
[
{
"_id": 1,
"id": 1,
"pid": 0,
"city_code": "101010100",
"city_name": "北京"
},
{
"_id": 2,
"id": 2,
"pid": 0,
"city_code": "",
"city_name": "安徽"
},
{
"_id": 3,
"id": 3,
"pid": 0,
"city_code": "",
"city_name": "福建"
},
{
"_id": 4,
"id": 4,
"pid": 0,
"city_code": "",
"city_name": "甘肃"
},
{
"_id": 5,
"id": 5,
"pid": 0,
"city_code": "",
"city_name": "广东"
},
{
"_id": 7,
"id": 7,
"pid": 0,
"city_code": "",
"city_name": "贵州"
},
{
"_id": 15,
"id": 15,
"pid": 0,
"city_code": "",
"city_name": "江苏"
},
{
"_id": 24,
"id": 24,
"pid": 0,
"city_code": "101020100",
"city_name": "上海"
},
{
"_id": 25,
"id": 25,
"pid": 0,
"city_code": "",
"city_name": "四川"
},
{
"_id": 26,
"id": 26,
"pid": 0,
"city_code": "101030100",
"city_name": "天津"
}
]
代码如下：
package day03;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
import com.alibaba.fastjson.*;
public class CityJsonTest {
public static void main(String[] args) throws Exception{
// 创建一个可关闭的客户端工具
CloseableHttpClient client = HttpClients.createDefault();
// 创建一个GET请求
HttpGet request = new HttpGet("http://cdn.sojson.com/_city.json");
// 发送该请求
HttpResponse response = client.execute(request);
// 将响应正文（body）转换字符串
String data = EntityUtils.toString(response.getEntity());
// 将data解析为JSON数组
JSONArray cities = JSON.parseArray(data);
//
for(Object city:cities){
JSONObject obj = (JSONObject)city;
//
if(obj.get("city_name").equals("上海")){
System.out.println(obj.get("city_code"));//101020100
break;
}
}
client.close();//关闭给客户端
}
}
将json格式的字符串转成json对象
天气预报json数据的解析思路：
1）将整个json串解析为JSON对象
JSONObject obj= JSON.parseObject(str2);
2）通过属性名获取属性的内容
JSONObject data = obj.getJSONObject("data");
3）如果解析出来的内容是对象的话，可进一步通过属性名获取里面的内容
JSONArray forecast = data.getJSONArray("forecast");
4）如果解析出来的内容是数组的话，可进一步通过下标获取里面的内容
JSONObject tomorrow = (JSONObject)forecast.get(1);
代码如下：
package day03;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONArray;
import com.alibaba.fastjson.JSONObject;
public class WeatherJsonTest {
public static void main(String[] args) throws Exception {
//
String cityCode = null;
// 创建一个可关闭的客户端工具
CloseableHttpClient client = HttpClients.createDefault();
// 创建一个GET请求
HttpGet request = new HttpGet("http://cdn.sojson.com/_city.json");
// 发送该请求
HttpResponse response = client.execute(request);
// 将响应正文（body）转换字符串
String str = EntityUtils.toString(response.getEntity());
// 将str解析为JSON数组
JSONArray cities = JSON.parseArray(str);
//
for(Object city:cities){
JSONObject obj = (JSONObject)city;
//
if(obj.get("city_name").equals("上海")){
//System.out.println(obj.get("city_code"));//101020100
cityCode = obj.getString("city_code");
break;
}
}
//创建一个请求天气的Get请求
HttpGet request2 = new HttpGet("http://t.weather.sojson.com/api/weather/city/"+cityCode);
//发送该请求
HttpResponse response2 = client.execute(request2);
// 将响应正文（body）转换字符串
String str2 = EntityUtils.toString(response2.getEntity());
//将str2解析为JSON对象
JSONObject obj= JSON.parseObject(str2);
//获取data属性的内容
JSONObject data = obj.getJSONObject("data");
//获取forecast属性的内容
JSONArray forecast = data.getJSONArray("forecast");
//获取明天的天气
JSONObject tomorrow = (JSONObject)forecast.get(1);
System.out.println(tomorrow.get("type"));//小雨
System.out.println(tomorrow.getString("high"));//高温 26.0℃
System.out.println(tomorrow.getString("low"));//低温 20.0℃
client.close();//关闭给客户端
}
}
JSON字符串解析的小结
1）将表示对象的json串解析为对象使用parseObject(str)
2）将表示数组的json串解析为数组使用parseArray(str)
3）属性的值是对象的话，就使用getJSONObject获取属性的内容
4）属性的值是数组的话，就使用getJSONArray获取该属性的内容
5）属性的值是字符串的话，就使用get或者getString获取该属性的内容
6）属性的值是数值的话，就使用get获取该属性的内容
7）属性的值是布尔值的话，就使用get获取该属性的内容
将对象转成json格式的字符串
代码如下：
package day03;
import java.util.Date;
import com.alibaba.fastjson.JSON;
import com.testin.model.Dept;
import com.testin.model.Employee;
public class ObjectToJSONTest {
public static void main(String[] args) {
Dept dept = new Dept(10,"研发","上海");
Employee emp = new Employee(1001,"张三",true,new Date(),dept);
//将部门对象转成json格式的字符串
System.out.println(JSON.toJSONString(dept));
//
System.out.println(JSON.toJSONString(emp));
}
}
运行结果如下：
{"dname":"研发","dno":10,"loc":"上海"}
{"dept":{"dname":"研发","dno":10,"loc":"上海"},"empno":1001,"ename":"张三","hiredate":1557978889881,"male":true}
员工模板的代码如下：
package com.testin.model;
import java.util.Date;
public class Employee {
private int empno;
private String ename;
private boolean isMale;
private Date hiredate;
private Dept dept;
public Employee(int empno, String ename, boolean isMale, Date hiredate, Dept dept) {
super();
this.empno = empno;
this.ename = ename;
this.isMale = isMale;
this.hiredate = hiredate;
this.dept = dept;
}
public int getEmpno() {
return empno;
}
public void setEmpno(int empno) {
this.empno = empno;
}
public String getEname() {
return ename;
}
public void setEname(String ename) {
this.ename = ename;
}
public boolean isMale() {
return isMale;
}
public void setMale(boolean isMale) {
this.isMale = isMale;
}
public Date getHiredate() {
return hiredate;
}
public void setHiredate(Date hiredate) {
this.hiredate = hiredate;
}
public Dept getDept() {
return dept;
}
public void setDept(Dept dept) {
this.dept = dept;
}
}
部门模板的代码如下：
package com.testin.model;
public class Dept {
private int dno;
private String dname;
private String loc;
public Dept(int dno, String dname, String loc) {
super();
this.dno = dno;
this.dname = dname;
this.loc = loc;
}
public int getDno() {
return dno;
}
public void setDno(int dno) {
this.dno = dno;
}
public String getDname() {
return dname;
}
public void setDname(String dname) {
this.dname = dname;
}
public String getLoc() {
return loc;
}
public void setLoc(String loc) {
this.loc = loc;
}
}
将对象集合转成json格式的字符串
代码如下：
package day03;
import java.util.ArrayList;
import java.util.List;
import com.alibaba.fastjson.JSON;
import com.testin.model.Dept;
public class ListToJSONTest {
public static void main(String[] args) {
// TODO Auto-generated method stub
List<Dept> depts = new ArrayList<Dept>();
Dept d1 = new Dept(10,"研发","上海");
Dept d2 = new Dept(20,"销售","上海");
depts.add(d1);
depts.add(d2);
System.out.println(JSON.toJSONString(depts));
}
}
运行结果如下：
[{"dname":"研发","dno":10,"loc":"上海"},{"dname":"销售","dno":20,"loc":"上海"}]
参考资料
[1] json语法
https://www.runoob.com/json/json-syntax.html
[2] JSON最佳实践
http://kimmking.github.io/2017/06/06/json-best-practice/
[3] fastjson教程
https://www.w3cschool.cn/fastjson
[4] Json详解以及fastjson使用教程
https://blog.csdn.net/srj1095530512/article/details/82529759
[5] fastjson新手指南
https://github.com/alibaba/fastjson/wiki/Quick-Start-CN
[6] 天气预报接口API文档
https://www.juhe.cn/docs/api/id/73
[7] 免费天气API，天气JSON API，不限次数获取十五天的天气预报
https://www.sojson.com/blog/305.html
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