java如何实现抽取json文件指定字段值-Java开发

这篇文章主要介绍了java如何实现抽取json文件指定字段值，具有很好的参考价值，希望对大家有所帮助。

使用场景

我有一个5000条数据的json文件，每条数据包含地名、该地的经纬度等其他很多信息。现在想把地名和经纬度抽出来导入到数据库中。

navicat自带的导入json格式文件不好用，只能导入json文件中的外层数据，而我需要的地名和经纬度信息在json的内层。

抽取json指定字段值

json文件格式

{
	"type": "FeatureCollection",
	"features": [{
			"type": "Feature",
			"geometry": {
				"type": "Point",
				"coordinates": [117.135437, 39.22393]
			},
			"properties": {
				"type": 1,
				"OBJECTID": 9288,
				"CC": "1117",
				"GB": "310107",
				"NAME": "某某村",
				"PAC": "120104008006111",
				"ELEMSTIME": "20150630",
				"ELEMETIME": "",
				"AREACODE": 120000,
				"FEATID": 120000403,
				"ChangeType": 0,
				"ChangeAtt": ""
			}
		},
		{
			"type": "Feature",
			"geometry": {
				"type": "Point",
				"coordinates": [117.17052343, 39.124663697000074]
			},
			"properties": {
				"OBJECTID": 9289,
				"CC": "1117",
				"GB": "310107",
				"NAME": "某某社区",
				"PAC": "120104003014111",
				"ELEMSTIME": "20150630",
				"ELEMETIME": "",
				"AREACODE": 120000,
				"FEATID": 120000458,
				"ChangeType": 0,
				"ChangeAtt": ""
			}
		}
	]
}

导入依赖

在pom.xml文件里加上fastjson

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.9</version>
</dependency>

代码实现

读取本地json文件的方法

public static String readJsonFile(String fileName) {
    String jsonStr = "";
    try {
        File jsonFile = new File(fileName);
        FileReader fileReader = new FileReader(jsonFile);
        Reader reader = new InputStreamReader(new FileInputStream(jsonFile), "utf-8");
        int ch = 0;
        StringBuffer sb = new StringBuffer();
        while ((ch = reader.read()) != -1) {
            sb.append((char) ch);
        }
        fileReader.close();
        reader.close();
        jsonStr = sb.toString();
        return jsonStr;
    } catch (IOException e) {
        e.printStackTrace();
        return null;
    }
}

读取指定字段

先把json文件放在resourses下面（直接复制到resourses）

String path = ddem.class.getClassLoader().getResource("villagePoint.json").getPath();
String s = readJsonFile(path);
JSONObject jobj = JSON.parseObject(s);
JSONArray features = jobj.getJSONArray("features");//构建JSONArray数组
for (int i = 0; i < features.size(); i++) {
    JSONObject key = (JSONObject) features.get(i);
    JSONObject geometry =key.getJSONObject("geometry");
    JSONArray coordinates=geometry.getJSONArray("coordinates");
    BigDecimal jingdu = coordinates.getBigDecimal(0);
    BigDecimal weidu = coordinates.getBigDecimal(1);
    JSONObject properties=key.getJSONObject("properties");
    String name =(String)properties.getString("NAME");
//          System.out.println(jingdu);
//          System.out.println(weidu);
    System.out.println(name);
}

JSONObject或JSONArray可以get很多种类型，具体用哪个看你自己的json内容

完整代码

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONArray;
import com.alibaba.fastjson.JSONObject;
import java.io.*;
import java.math.BigDecimal;
public class ddem {
    public static void main(String[] args) {
        String path = ddem.class.getClassLoader().getResource("villagePoint.json").getPath();
        String s = readJsonFile(path);
        JSONObject jobj = JSON.parseObject(s);
        JSONArray features = jobj.getJSONArray("features");//构建JSONArray数组
        for (int i = 0; i < features.size(); i++) {
            JSONObject key = (JSONObject) features.get(i);
            JSONObject geometry =key.getJSONObject("geometry");
            JSONArray coordinates=geometry.getJSONArray("coordinates");
            BigDecimal jingdu = coordinates.getBigDecimal(0);
            BigDecimal weidu = coordinates.getBigDecimal(1);
            JSONObject properties=key.getJSONObject("properties");
            String name =(String)properties.getString("NAME");
//          System.out.println(jingdu);
//          System.out.println(weidu);
            System.out.println(name);
        }
    }
    //读取json文件
    public static String readJsonFile(String fileName) {
        String jsonStr = "";
        try {
            File jsonFile = new File(fileName);
            FileReader fileReader = new FileReader(jsonFile);
            Reader reader = new InputStreamReader(new FileInputStream(jsonFile), "utf-8");
            int ch = 0;
            StringBuffer sb = new StringBuffer();
            while ((ch = reader.read()) != -1) {
                sb.append((char) ch);
            }
            fileReader.close();
            reader.close();
            jsonStr = sb.toString();
            return jsonStr;
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
    }
}