อ่าน/Parse JSON Array ด้วย Java (json-simple library)

JSON Array คอลเลกชันค่าลำดับใน [ ... ] คั่น comma ใช้ json-simple library อ่านได้

Maven Dependency

<dependency>
    <groupId>com.googlecode.json-simple</groupId>
    <artifactId>json-simple</artifactId>
    <version>1.1.1</version>
</dependency>

ไฟล์ JSON ตัวอย่าง (sample.json)

{
  "ID": "1",
  "First_Name": "Krishna Kasyap",
  "Last_Name": "Bhagavatula",
  "Date_Of_Birth": "1989-09-26",
  "Place_Of_Birth": "Vishakhapatnam",
  "Salary": "25000",
  "contact": [
    "e-mail: krishna_kasyap@gmail.com",
    "phone: 9848022338",
    "city: Hyderabad",
    "Area: Madapur",
    "State: Telangana"
  ]
}

ขั้นตอนอ่าน JSON Array

1. สร้าง JSONParser
2. Parse ไฟล์ด้วย parse(FileReader) ได้ JSONObject
3. ดึงค่าปกติด้วย get("key")
4. ดึง Array ด้วย get("contact") cast เป็น JSONArray
5. วนลูปด้วย iterator() ของ JSONArray

ตัวอย่างโค้ดเต็ม

import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.Iterator;
import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
import org.json.simple.parser.ParseException;

public class ReadingArrayFromJSON {
    public static void main(String args[]) {
        JSONParser jsonParser = new JSONParser();
        
        try {
            // Parse JSON file
            JSONObject jsonObject = (JSONObject) jsonParser.parse(new FileReader("E:/test.json"));
            
            System.out.println("Contents of the JSON are: ");
            System.out.println("ID: " + jsonObject.get("ID"));
            System.out.println("First name: " + jsonObject.get("First_Name"));
            System.out.println("Last name: " + jsonObject.get("Last_Name"));
            System.out.println("Date of birth: " + jsonObject.get("Date_Of_Birth"));
            System.out.println("Place of birth: " + jsonObject.get("Place_Of_Birth"));
            System.out.println("Salary: " + jsonObject.get("Salary"));
            
            // ดึง Array
            JSONArray jsonArray = (JSONArray) jsonObject.get("contact");
            System.out.println("\nContact details: ");
            
            // Iterate array
            Iterator iterator = jsonArray.iterator();
            while (iterator.hasNext()) {
                System.out.println(iterator.next());
            }
        } catch (FileNotFoundException | IOException | ParseException e) {
            e.printStackTrace();
        }
    }
}

ผลลัพธ์

Contents of the JSON are:
ID: 1
First name: Krishna Kasyap
Last name: Bhagavatula
Date of birth: 1989-09-26
Place of birth: Vishakhapatnam
Salary: 25000

Contact details:
e-mail: krishna_kasyap@gmail.com
phone: 9848022338
city: Hyderabad
Area: Madapur
State: Telangana

หมายเหตุ

• json-simple คืนค่าเป็น Object ต้อง cast
• JSONArray.iterator() คืน Iterator ของค่าใน array
• จัดการ Exception: FileNotFoundException, IOException, ParseException