Java program to fetch JSON data

To fetch JSON data in Java, we typically use libraries like java.net for HTTP requests and a JSON parsing library like org.json, Gson, or Jackson to parse the JSON data. Below is an example using HttpURLConnection from the java.net package to fetch JSON data from a URL and parse it using the org.json library.

Fetching JSON Data Using Java:

Here’s a simple example using HttpURLConnection and org.json:

• Add Dependencies: If we’re using Maven, add the following dependency for org.json:

  <dependency>
      <groupId>org.json</groupId>
      <artifactId>json</artifactId>
      <version>20230227</version>
  </dependency>
  

  If not using Maven, make sure to download and add the library to your classpath.

• Java Code:

  import java.io.BufferedReader;
  import java.io.InputStreamReader;
  import java.net.HttpURLConnection;
  import java.net.URL;
  import org.json.JSONObject;
  
  public class FetchJsonData {
  
      public static void main(String[] args) {
          String urlString = "https://api.example.com/data";  // Replace with your URL
  
          try {
              // Create URL object
              URL url = new URL(urlString);
              
              // Open a connection
              HttpURLConnection conn = (HttpURLConnection) url.openConnection();
              conn.setRequestMethod("GET");
              conn.setRequestProperty("Accept", "application/json");
  
              // Check if the request was successful
              if (conn.getResponseCode() != 200) {
                  throw new RuntimeException("Failed : HTTP error code : " + conn.getResponseCode());
              }
  
              // Read the response
              BufferedReader br = new BufferedReader(new InputStreamReader((conn.getInputStream())));
              StringBuilder response = new StringBuilder();
              String output;
              while ((output = br.readLine()) != null) {
                  response.append(output);
              }
  
              // Close the connection
              conn.disconnect();
  
              // Parse JSON response
              JSONObject jsonResponse = new JSONObject(response.toString());
  
              // Example of accessing data from JSON
              System.out.println("Response: " + jsonResponse.toString(2)); // Pretty print JSON with indentation of 2
  
          } catch (Exception e) {
              e.printStackTrace();
          }
      }
  }
  

  Key Points:

  HTTP Request: The code uses HttpURLConnection to make an HTTP GET request to the specified URL.

• Reading Response: It reads the response from the server using BufferedReader.

• Parsing JSON: The response is parsed into a JSONObject using the org.json library.
• Handling Errors: Make sure to handle exceptions like IOException and check the response code to ensure the request was successful.