How to send HTTP request GET/POST in Java

In this post, we will see how to send HTTP Get/Post in java.
There are many times when you need to send http get or post request. You can use HttpURLConnection for sending get/post request in java. It belongs to java.net package.

HttpURLConnection example:

We are going to send get or post request to URLs used in restful web services CRUD example, so instead of using PostMan , we will send request using java.

Get Url:

http://localhost:8080/JAXRSJsonCRUDExample/rest/countries
It will give you list of country in json format.

Post URL:

http://localhost:8080/JAXRSJsonCRUDExample/rest/countries
Post data:{"id":5,"countryName":"USA","population":8000}
It will create a new country resource and add it to list of counties.
Java code:
package org.arpit.java2blog.corejava;

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
/**
 * @author Arpit Mandliya
 */
public class HttpURLConnectionExample {

 private final String USER_AGENT = "Mozilla/5.0";

 public static void main(String[] args) throws Exception {

  HttpURLConnectionExample http = new HttpURLConnectionExample();

     // Sending get request
  http.sendingGetRequest();
  
    // Sending post request
  http.sendingPostRequest();

 }

 // HTTP GET request
 private void sendingGetRequest() throws Exception {

  String urlString = "http://localhost:8080/JAXRSJsonCRUDExample/rest/countries";
  
  URL url = new URL(urlString);
  HttpURLConnection con = (HttpURLConnection) url.openConnection();

  // By default it is GET request
  con.setRequestMethod("GET");

  //add request header
  con.setRequestProperty("User-Agent", USER_AGENT);

  int responseCode = con.getResponseCode();
  System.out.println("Sending get request : "+ url);
  System.out.println("Response code : "+ responseCode);

  // Reading response from input Stream
  BufferedReader in = new BufferedReader(
          new InputStreamReader(con.getInputStream()));
  String output;
  StringBuffer response = new StringBuffer();

  while ((output = in.readLine()) != null) {
   response.append(output);
  }
  in.close();

  //printing result from response
  System.out.println(response.toString());

 }
 
 // HTTP Post request
 private void sendingPostRequest() throws Exception {

  String url = "http://localhost:8080/JAXRSJsonCRUDExample/rest/countries";
  URL obj = new URL(url);
  HttpURLConnection con = (HttpURLConnection) obj.openConnection();

        // Setting basic post request
  con.setRequestMethod("POST");
  con.setRequestProperty("User-Agent", USER_AGENT);
  con.setRequestProperty("Accept-Language", "en-US,en;q=0.5");
  con.setRequestProperty("Content-Type","application/json");

  String postJsonData = "{\"id\":5,\"countryName\":\"USA\",\"population\":8000}";
  
  // Send post request
  con.setDoOutput(true);
  DataOutputStream wr = new DataOutputStream(con.getOutputStream());
  wr.writeBytes(postJsonData);
  wr.flush();
  wr.close();

  int responseCode = con.getResponseCode();
  System.out.println("\nSending 'POST' request to URL : " + url);
  System.out.println("Post Data : " + postJsonData);
  System.out.println("Response Code : " + responseCode);

  BufferedReader in = new BufferedReader(
          new InputStreamReader(con.getInputStream()));
  String output;
  StringBuffer response = new StringBuffer();

  while ((output = in.readLine()) != null) {
   response.append(output);
  }
  in.close();
  
  //printing result from response
  System.out.println(response.toString());
 }
}
When you run above program, you will get below output:
Sending get request : http://localhost:8080/JAXRSJsonCRUDExample/rest/countries
Response code : 200
[{"id":1,"countryName":"India","population":10000},{"id":2,"countryName":"Bhutan","population":7000},{"id":3,"countryName":"Nepal","population":8000},{"id":4,"countryName":"China","population":20000}]

Sending 'POST' request to URL : http://localhost:8080/JAXRSJsonCRUDExample/rest/countries
Post Data : {"id":5,"countryName":"USA","population":8000}
Response Code : 200
{"id":5,"countryName":"USA","population":8000}
If you comment http.sendingPostRequest(); and send only get request. You will get below output:
[{"id":1,"countryName":"India","population":10000},{"id":2,"countryName":"Bhutan","population":7000},{"id":3,"countryName":"Nepal","population":8000},{"id":4,"countryName":"China","population":20000},
{"id":5,"countryName":"USA","population":8000}]
You can see USA is added to country list.

Written by Arpit:

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