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Java HttpURLConnection Example

The Java java.net.HttpURLConnection class is used to send a HTTP request. Although it is old and not user-friendly, sometimes it is the only option for some legacy projects. In this article, I will show you how to send GET and POST requests to Go Rest, which is a fake or an online REST API for testing and prototyping.

Maven Dependencies #

Add the following dependencies for parsing the results, of course you can use other libraries such as Gson.

<dependency>
  <groupId>org.json</groupId>
  <artifactId>json</artifactId>
  <version>20210307</version>
</dependency>

GET Request #

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

import org.json.JSONObject;

public class HttpURLConnectionGetExample {
  public static void main(String[] args) throws Exception {
    String endpoint = "https://gorest.co.in/public/v1/users";
    URL url = new URL(endpoint);
    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
    connection.setRequestMethod("GET");

    BufferedReader responseReader =
      new BufferedReader(new InputStreamReader(connection.getInputStream()));

    String temp;
    StringBuilder response = new StringBuilder();
    while ((temp = responseReader.readLine()) != null) {
      response.append(temp);
    }
    responseReader.close();

    JSONObject result = new JSONObject(response.toString());
    System.out.println(result.get("meta"));
  }
}

Output:

{"pagination":{"total":2145,"pages":108,"limit":20,"links":{"next":"https://gorest.co.in/public/v1/users?page=2","current":"https://gorest.co.in/public/v1/users?page=1","previous":null},"page":1}}

POST Request #

Note that you need to get access token first!

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;

import org.json.JSONObject;

public class HttpURLConnectionPostExample {
  public static void main(String[] args) throws Exception {
    String endpoint = "https://gorest.co.in/public/v1/users";
    URL url = new URL(endpoint);
    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
    connection.setRequestMethod("POST");
    connection.setRequestProperty("Content-Type", "application/json");
    String accessToken = "accessToken";
    connection.setRequestProperty("Authorization", "Bearer " + accessToken);
    connection.setDoOutput(true);

    String json = "{\"name\":\"john123\", \"gender\":\"male\","
      + "\"email\":\"abc@def.com\",\"status\":\"active\"}";

    try(OutputStream os = connection.getOutputStream()) {
      byte[] input = json.getBytes("utf-8");
      os.write(input, 0, input.length);
      os.flush();
      os.close();
    }

    BufferedReader responseReader =
        new BufferedReader(new InputStreamReader(connection.getInputStream()));

      String temp;
      StringBuilder response = new StringBuilder();
      while ((temp = responseReader.readLine()) != null) {
        response.append(temp);
      }
      responseReader.close();

      JSONObject result = new JSONObject(response.toString());
      System.out.println(result);
  }
}

Output:

{"data":{"gender":"male","name":"john123","id":2772,"email":"abc@def.com","status":"active"},"meta":null}