前言

Java 读取Json文件的内容。

pom 依赖

 <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>fastjson</artifactId>
        <version>1.2.47</version>
 </dependency>
 
<dependency>
            <groupId>commons-io</groupId>
            <artifactId>commons-io</artifactId>
            <version>2.6</version>
        </dependency>

程序

• Json文件

{
  "station":[
    {
      "dbm":-83,
      "lac":0,
      "mcc":"460",
      "mnc":"11",
      "psc":0,
      "sid":0,
      "type":"Lte"
    }
  ],
  "mac":[
    {
      "id":"enyouh",
      "mac":"b8:80:35:e6:68:51",
      "str":"-89"
    }
  ]
}

• 程序

package study.nian.project01;

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONObject;

import java.io.File;
import java.io.IOException;
import org.apache.commons.io.FileUtils;

public class QueryJson {

    public static void main(String[] args) {
        
        JSONObject jsonObject = new JSONObject();
        jsonObject.put("stationList", "[{\"cid\":125702705, \"dbm\":-83, \"lac\":0, \"mcc\":\"460\", \"mnc\":\"11\", \"psc\":0, \"sid\":0, \"type\":\"Lte\" }]");
        jsonObject.put("macList", "[{\"id\":\"enyouhuayi-5G\",\"mac\":\"b8:80:35:e6:68:51\",\"str\":\"-89\"}]");
        System.out.println("jsonObject的K：stationList，V：" + jsonObject.getString("stationList"));
        System.out.println("jsonObject的K：macList，V：" + jsonObject.getString("macList"));

        try {
            File file = new File("./src/main/java/study/nian/project01/entity/ea.json") ;
            String content = FileUtils.readFileToString(file,"UTF-8");
            JSONObject jsonObj = JSON.parseObject(content);

            System.out.println("K：stationList，V：" + jsonObj.getString("station"));
            System.out.println("K：macList，V：" + jsonObj.getString("mac"));

        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}

结果展示

jsonObject的K：stationList，V：[{"cid":125702705, "dbm":-83, "lac":0, "mcc":"460", "mnc":"11", "psc":0, "sid":0, "type":"Lte" }]
jsonObject的K：macList，V：[{"id":"enyouhuayi-5G","mac":"b8:80:35:e6:68:51","str":"-89"}]
K：stationList，V：[{"psc":0,"mnc":"11","mcc":"460","type":"Lte","dbm":-83,"lac":0,"sid":0}]
K：macList，V：[{"str":"-89","id":"enyouh","mac":"b8:80:35:e6:68:51"}]

总结

• 文件的话，FileUtils的使用，pom文件加载
• Json文件K-V存储，加入数据用put（）方法

import com.alibaba.fastjson.JSONArray;
import com.alibaba.fastjson.JSONObject;
import java.io.*;
public class test {
public static void main(String[] args) throws IOException {
        //读取json文件
        JSONObject jsonObject = JSONObject.parseObject(new FileInputStream("E:/config.json"), JSONObject.class);
        jsonObject.put("param","1");
        //写入json文件，这里是覆盖原文件
        BufferedWriter bw = new BufferedWriter(new FileWriter("E:/config.json"));
        bw.write(jsonObject.toString());
        bw.close();
        
        //类似的，读写JSONArray如下
        JSONArray jsonArray = JSONArray.parseObject(new FileInputStream("E:/config.json"), JSONArray.class);
        String configContent = "{\"param\": \"1\"}";
        jsonArray.add(JSONObject.parseObject(configContent));
        BufferedWriter bw = new BufferedWriter(new FileWriter("E:/config.json"));
        bw.write(jsonArray.toString());
        bw.close();
}

先下载一个 json.jar 库

下载地址

下载完后就加到工程里，然后才可以使用别人已封装好的方法，下载这个jar后，就不需要添加其他的依赖了。

代码如下：

package MenuTreePack;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.io.*;
import java.util.ArrayList;

public class json_do {
    public static void Test() {
        ArrayList<String> list = new ArrayList<String>();
        list.add("admin");

        JSONObject dataJson = ReadJson("test.json");//new JSONObject(data);
        JSONArray features=dataJson.getJSONArray("features");
        for (int i = 0; i < features.length(); i++) {
            JSONObject info = features.getJSONObject(i);// 获取features数组的第i个json对象
            JSONObject properties = info.getJSONObject("properties");// 找到properties的json对象
            String name = properties.getString("name");// 读取properties对象里的name字段值
            System.out.println(name);

            properties.put("NAMEID", list.get(i));// 添加NAMEID字段
            // properties.append("name", list.get(i));
            System.out.println(properties.getString("NAMEID"));

            properties.remove("ISO");// 删除ISO字段

            WriteJson("newFile.json", dataJson);
        }
    }


    public static JSONObject ReadJson(String Path){
        JSONObject dataJson = null;
        //读取json文件
        try {
            BufferedReader br = new BufferedReader(new FileReader(Path));
            String str=null;
            String data="";
            while((str=br.readLine())!=null) {
                data=data+str+"\n";
            }
            dataJson = new JSONObject(data);
            br.close();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }// 读取原始json文件
        catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return dataJson;
    }

    public static void WriteJson(String Path, JSONObject dataJson) {
        //读取json文件
        try {
            BufferedWriter bw=new BufferedWriter(new FileWriter(Path));
            String ws=dataJson.toString();
            System.out.println(ws);
            bw.write(ws);
            // bw.newLine();
            bw.flush();
            bw.close();

        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }// 读取原始json文件
        catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

}

对应的测试用json文件为:

{
	"type": "FeatureCollection",  
    "features": 
	[
		{  
			"type": "Feature",  
			"properties": 
			{  
				"name": "Yuen Long",  
				"ID_0": 102,  
				"ISO": "HKG"  
			},  
			"geometry": 
			{  
				"type": "Polygon",  
				"coordinates": 
				[
					[
						[
							114.084511, 
							22.519991
						], 
						[
							114.075668, 
						], 
					]
				]  
			}  
		}
	]
}

本文参考： https://blog.csdn.net/qq_23335979/article/details/81668604?utm_medium=distribute.pc_relevant.none-task-blog-BlogCommendFromMachineLearnPai2-3.control&dist_request_id=1328680.64143.16164822381121313&depth_1-utm_source=distribute.pc_relevant.none-task-blog-BlogCommendFromMachineLearnPai2-3.control