读取 JSON 键：值对

Question

我读取了整个 JSON 文件，但我需要从 key rating 中读取值并存储到 ArrayList 中，这是代码但它没有做任何事情

        ArrayList<Object> rates = new ArrayList<>();

        FileReader read = new FileReader("C:\\Users\\User\\eclipse-workspace\\Task\\files\\reviews.json");
        JSONParser parser = new JSONParser();
        Object obj = parser.parse(read);
        JSONObject jsonObject = new JSONObject();
        jsonObject = (JSONObject) obj;

        JSONArray reviews = new JSONArray();
        reviews = (JSONArray) jsonObject.get("reviews");

        Iterator<Entry> itr1 = reviews.iterator();
        while (itr1.hasNext()) {

            Map rate= ((Map)jsonObject.get("rating"));
            Iterator<Entry> itr2 = ((JSONObject) itr1.next()).entrySet().iterator();
            while (itr2.hasNext()) {
                if(itr2.equals("rating")) {
                rates.add(itr2);
                Map.Entry pair = itr2.next();
                System.out.println(rate);
            }
        }
        }
        
        

Answer 1

根据您的提示和示例代码，此代码 sn-p 可以帮助您

import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
import org.json.simple.parser.ParseException;
import org.junit.jupiter.api.Test;

import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;

public class TestQ68867649 {

    @Test
    void testQ68867649() throws IOException, ParseException {
        ArrayList<Long> rates = new ArrayList();

        FileReader read = new FileReader("C:\\Users\\User\\eclipse-workspace\\Task\\files\\reviews.json");
        
        JSONParser parser = new JSONParser();
        Object obj = parser.parse(read);
        JSONObject jsonObject = (JSONObject) obj;

        JSONArray reviews = (JSONArray) jsonObject.get("reviews");

        for (Iterator<JSONObject> iterator = reviews.iterator(); iterator.hasNext(); ) {
            JSONObject rate = iterator.next();
            rates.add((Long) rate.get("rating"));
        }

        System.out.println("rates values: " + rates);
    }
}

reviews.json 文件示例数据基于您提供的数据

{
  "reviews": [
    {
      "id": 2097047,
      "reviewId": "93f131be27dc1122bb7ef0048ad10e4f",
      "reviewFullText": "5 star review",
      "reviewText": "5 star review",
      "numLikes": 0,
      "numComments": 0,
      "numShares": 0,
      "rating": 5,
      "reviewCreatedOn": "2 months ago"
    },
    {
      "id": 2097047,
      "reviewId": "93f131be27dc1122bb7ef0048ad10e4f",
      "reviewFullText": "5 star review",
      "reviewText": "5 star review",
      "numLikes": 0,
      "numComments": 0,
      "numShares": 0,
      "rating": 3,
      "reviewCreatedOn": "2 months ago"
    }
  ]
}

输出基于用作示例的数据 rates values: [5, 3]

pom.xml 文件

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>q68867649</artifactId>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter</artifactId>
            <version>RELEASE</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>com.googlecode.json-simple</groupId>
            <artifactId>json-simple</artifactId>
            <version>1.1.1</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
</project>

注意：此示例是使用 Java 8 和 Maven 开发的

Answer 2

根据您目前提供的内容，也许这段代码 sn-p 会给您一些想法：

import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
import org.json.simple.parser.ParseException;

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

// This will be what you have in your JSON file.
String content = "{\n" +
        "  \"reviews\": [\n" +
        "    {\n" +
        "      \"id\": 2097047,\n" +
        "      \"reviewId\": \"93f131be27dc1122bb7ef0048ad10e4f\",\n" +
        "      \"reviewFullText\": \"5 star review\",\n" +
        "      \"reviewText\": \"5 star review\",\n" +
        "      \"numLikes\": 0,\n" +
        "      \"numComments\": 0,\n" +
        "      \"numShares\": 0,\n" +
        "      \"rating\": 5,\n" +
        "      \"reviewCreatedOn\": \"2 months ago\"\n" +
        "    },\n" +
        "    {\n" +
        "      \"id\": 2097048,\n" +
        "      \"reviewId\": \"123131be27dc1122bb7ef0048ad10e4f\",\n" +
        "      \"reviewFullText\": \"4 star review\",\n" +
        "      \"reviewText\": \"4 star review\",\n" +
        "      \"numLikes\": 0,\n" +
        "      \"numComments\": 0,\n" +
        "      \"numShares\": 0,\n" +
        "      \"rating\": 4,\n" +
        "      \"reviewCreatedOn\": \"3 months ago\"\n" +
        "    }\n" +
        "  ]\n" +
        "}";

JSONParser parser = new JSONParser();
List<Integer> rates = new ArrayList<>();

try {
    JSONObject jsonObject = (JSONObject) parser.parse(content);
    JSONArray jsonArray = (JSONArray) jsonObject.get("reviews");
    
    for (Iterator<JSONObject> itr = jsonArray.iterator(); itr.hasNext();) {
        JSONObject item = itr.next();

        // do your stuff here for rating. I simply added it in the list right here.
        rates.add(((Long) item.get("rating")).intValue());
    }
} catch (ParseException e) {
    // handle exception
}