java获取json中某个字段

import com.alibaba.fastjson.JSONObject;
public class JsonTest {public static void main(String[] args) {// json串(以自己的为准)String str = "{"id":"75","shoppingCartItemList":[{"id":"407","num":"10"}]}";JSONObject jsonObject = JSONObject.parseObject(str);// 获取到key为shoppingCartItemList的值String r = jsonObject.getString("shoppingCartItemList");System.out.println(r);}
}

package com.cmbc.cms.action.addrebatchno; import java.util.List; import com.alibaba.fastjson.JSONObject; public class Test { private int id; private int num; public int getId() { return id; } public void setId(int id) { this.id = id; } public int getNum() { return num; } public void setNum(int num) { this.num = num; } public static void main(String[] args) { // TODO Auto-generated method stub String str = "{\"id\":\"75\",\"shoppingCartItemList\":[{\"id\":\"407\",\"num\":\"10\"}]}"; JSONObject jsonObject = JSONObject.parseObject(str); // 获取到key为shoppingCartItemList的值 String r = jsonObject.getString("shoppingCartItemList"); System.out.println(r); //取外面的id String id = jsonObject.getString("id"); System.out.println(id); //取里面的id List<Test> list = JSONObject.parseArray(r,Test.class); int id2 = list.get(0).getId(); System.out.println(id2); }  
}

alibaba.fastjson.JSONObject.parseObject的使用

fastjson 是一个性能很好的 Java 语言实现的 JSON 解析器和生成器,当你要处理一段接收的json数据,就可以考虑使用JSONObject.parseObject

import com.alibaba.fastjson.JSONObject;

parseObject（String str）的作用

JSON.parseObject（String str）是将str转化为相应的JSONObject对象，其中str是“键值对”形式的json字符串，转化为JSONObject对象之后就可以使用其内置的方法，进行各种处理了。

json字段

{"code":0,"data":{"city":{"cityId":284609,"counname":"中国","ianatimezone":"Asia/Shanghai","name":"东城区","pname":"北京市","secondaryname":"北京市","timezone":"8"},"liveIndex":{"2021-03-17":[{"code":5,"day":"2021-03-17","desc":"天气较好，路面干燥，交通气象条件良好，车辆可以正常行驶。","level":"1","name":"交通指数","status":"良好","updatetime":"2021-03-17 06:24:03"},{"code":14,"day":"2021-03-17","desc":"天气较好，但丝毫不会影响您出行的心情。温度适宜又有微风相伴，适宜旅游。","level":"1","name":"旅游指数","status":"适宜","updatetime":"2021-03-17 06:24:03"}]}},"msg":"success","rc":{"c":0,"p":"success"}
}

{"code":0,"data":{"aqi":{"cityName":"东城区","co":"8","coC":"0.8","no2":"28","no2C":"56.0","o3":"2","o3C":"6.0","pm10":"160","pm10C":"270.0","pm25":"73","pm25C":"53.0","pubtime":"1615939200000","rank":"527/678","so2":"1","so2C":"3.0","value":"160"},"city":{"cityId":284609,"counname":"中国","ianatimezone":"Asia/Shanghai","name":"东城区","pname":"北京市","secondaryname":"北京市","timezone":"8"}},"msg":"success","rc":{"c":0,"p":"success"}
}

String json = EntityUtils.toString(response.getEntity());
JSONObject jsonObject = JSONObject.parseObject(json);
JSONObject date = jsonObject.getJSONObject("data");
JSONObject liveIndex = date.getJSONObject("liveIndex");
for (Map.Entry<String, Object> entry : liveIndex.entrySet()) {JSONArray jsonArray = liveIndex.getJSONArray(entry.getKey());for (Object object : jsonArray) {JSONObject object1 = (JSONObject) object;String name = object1.getString("code");String level = object1.getString("level");hashMap.put(name,level);}
}

String json = EntityUtils.toString(response.getEntity());
JSONObject jsonObject = JSONObject.parseObject(json);
JSONObject data = jsonObject.getJSONObject("data");
JSONObject api = data.getJSONObject("aqi");
String pm25C = api.getString("pm25C");

JSON.parseObject(String str)与JSONObject.parseObject(String str)的区别

根据源码显示：JSON是一个抽象类，JSON中有一个静态方法parseObject（String text），将text解析为一个JSONObject对象并返回；JSONObject是一个继承自JSON的类，当调用JSONObject.parseObject（result）时，会直接调用父类的parseObject（String text）。所以两者没什么区别，一个是用父类去调用父类自己的静态的parseObject（String text），一个是用子类去调用父类的静态parseObject（String text），两者调的是同一个方法。