java list转json 和json 转list 笔记

java list集合转json

    public static   void  getJson() throws JSONException {
        List<Person> personList = new ArrayList<Person>();
        for (int i = 0; i < 5; i++) {
            Person person=new Person();
            person.setName("xuiqing");
            person.setAge(20);
            person.setSex("男");
            personList.add(person);
        }
        JSONArray jsonArray = new JSONArray();
        JSONObject jsonObject = new JSONObject();
        JSONObject tmpObj = null;
        int count = personList.size();
        for(int i = 0; i < count; i++) {
            tmpObj = new JSONObject();
            tmpObj.put("name" , personList.get(i).name);
            tmpObj.put("sex", personList.get(i).sex);
            tmpObj.put("age", personList.get(i).age);
            jsonArray.put(tmpObj);
            tmpObj = null;
        }
        String personInfos = jsonArray.toString(); // 将JSONArray转换得到String
        jsonObject.put("personInfos" , personInfos);   // 获得JSONObject的String
        dataList(personInfos);
        System.out.println("personInfos    --- >  " +personInfos  );
    }

json 数组转list集合

 public  static   List<Person>dataList(String jsonstr){
        List<Person>getData=new ArrayList<>();
      if(jsonstr!=null&&jsonstr.length()>0){
          try {
              JSONArray  jsonArray=new JSONArray(jsonstr);
              JSONObject jsonObject=null;
              for (int i = 0; i <jsonArray.length() ; i++) {
                 jsonObject=jsonArray.getJSONObject(i);
                  Person person=new Person();
                  person.setName(jsonObject.optString("name"));
                  person.setAge(jsonObject.optInt("age"));
                  person.setSex(jsonObject.optString("sex"));
                  getData.add(person);
              }
          } catch (JSONException e) {
              e.printStackTrace();
          }
      }
      return  getData;
    }

bean类

package com.example.demo;
public class Person {
        public String name;
        public String sex;
        public int age;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
}

完整代码：

 package com.example.demo;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

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

@SpringBootApplication
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
        try {
            getJson();
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }

    public static   void  getJson() throws JSONException {
        List<Person> personList = new ArrayList<Person>();
        for (int i = 0; i < 5; i++) {
            Person person=new Person();
            person.setName("xuiqing");
            person.setAge(20);
            person.setSex("男");
            personList.add(person);
        }
        JSONArray jsonArray = new JSONArray();
        JSONObject jsonObject = new JSONObject();
        JSONObject tmpObj = null;
        int count = personList.size();
        for(int i = 0; i < count; i++) {
            tmpObj = new JSONObject();
            tmpObj.put("name" , personList.get(i).name);
            tmpObj.put("sex", personList.get(i).sex);
            tmpObj.put("age", personList.get(i).age);
            jsonArray.put(tmpObj);
            tmpObj = null;
        }
        String personInfos = jsonArray.toString(); // 将JSONArray转换得到String
        jsonObject.put("personInfos" , personInfos);   // 获得JSONObject的String
        dataList(personInfos);
        System.out.println("personInfos    --- >  " +personInfos  );
    }

    public  static   List<Person>dataList(String jsonstr){
        List<Person>getData=new ArrayList<>();
      if(jsonstr!=null&&jsonstr.length()>0){
          try {
              JSONArray  jsonArray=new JSONArray(jsonstr);
              JSONObject jsonObject=null;
              for (int i = 0; i <jsonArray.length() ; i++) {
                 jsonObject=jsonArray.getJSONObject(i);
                  Person person=new Person();
                  person.setName(jsonObject.optString("name"));
                  person.setAge(jsonObject.optInt("age"));
                  person.setSex(jsonObject.optString("sex"));
                  getData.add(person);
              }
          } catch (JSONException e) {
              e.printStackTrace();
          }
      }
      return  getData;
    }
}