JSON数组转Java List

全栈程序员站长

发布于 2022-09-25 12:38:41

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大家好，又见面了，我是你们的朋友全栈君。

本文使用alibaba开源项目fastjson与SourceForge开源项目JSON-lib两种方法转换json。

现有json文件user.json如下：

[
  {
    "userid": "309BCCE3-8525-4D33-9856-5084E24FD96F",
    "username": "林梦",
    "password": "19bdec7440acd44c669240ed534fc2f6",
    "partment": "专案一组",
    "tel": "123",
    "email": "meng@baal.xyz",
    "tag": "专案",
    "creater": "",
    "time": "2016-10-24T08:10:51.101Z",
    "token": ""
  },
  {
    "userid": "FDA8B18B-E6EB-4C80-8A4B-0B2B27AEB7E2",
    "username": "汪小雨",
    "password": "19bdec7440acd44c669240ed534fc2f6",
    "partment": "专案三组",
    "tel": "123",
    "email": "xiaoyu@baal.xyz",
    "tag": "专案",
    "creater": "",
    "time": "2016-10-24T08:12:28.869Z",
    "token": ""
  }
]

创建数据模型User类，属性如下：

public class User {
	private String userid;
	private String username;
	private String password;
	private String partment;
	private String tel;
	private String email;
	private String tag;
	private String creater;
	private String time;
	private String token;

	......
}

1、使用fastjson

读取json文件转化为list:

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.List;

import com.alibaba.fastjson.JSONArray;
import com.alibaba.fastjson.JSONObject;

public class JsonToList_fastjson {
	private static final String User_Path = "d:/user.json";
	private static final String Message_Path = "d:/message.json";
	
	public static List<User> getUsers() {
		String userString = fileToStr(User_Path);
		List<User> list = JSONObject.parseArray(userString,User.class);
		return list;
	}

	public static String fileToStr(String filepath) {
		File file = new File(filepath);
		StringBuffer sb = new StringBuffer();
		InputStreamReader isr = null;
		try {
			isr = new InputStreamReader(new FileInputStream(file), "UTF-8");
			while (isr.ready()) {
				sb.append((char) isr.read());
			}
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			try {
				isr.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
		return sb.toString();
	}

	public static void main (String [] args) {
		
		List<User> listUsers = getUsers();
		for (User user : listUsers) {
			System.out.println(user.getEmail());
		}

		JSONArray array = (JSONArray) JSONArray.toJSON(listUsers);
		System.out.println(array);
	}
}

2、使用JSON-lib，相关jar包也可以在这里下载

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.List;

import net.sf.json.JSONArray;

public class JsonToList {

	private static final String User_Path = "d:/user.json";

	@SuppressWarnings("unchecked")
	public static List<User> getUsers() {
		String userString = fileToStr(User_Path);
		JSONArray array = JSONArray.fromObject(userString);
		List<User> list = null;
		list = (List<User>) JSONArray.toCollection(array, User.class);

		return list;
	}

	public static String fileToStr(String filepath) {
		File file = new File(filepath);
		StringBuffer sb = new StringBuffer();
		InputStreamReader isr = null;
		try {
			isr = new InputStreamReader(new FileInputStream(file), "UTF-8");
			while (isr.ready()) {
				sb.append((char) isr.read());
			}
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			try {
				isr.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
		return sb.toString();
	}

	public static void main(String[] args) {

		List<User> list = getUsers();
		for (User user : list) {
			System.out.println(user.getUsername());
		}

		JSONArray array = JSONArray.fromObject(list);
		System.out.println(array);
	}
}

JSON-lib API ：Doc

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