How To Use Java HttpURLConnection for HTTP GET and POST Requests

Updated on November 19, 2022

How To Use Java HttpURLConnection for HTTP GET and POST Requests

Introduction

The HttpURLConnection class from java.net package can be used to send a Java HTTP Request programmatically. In this article, you will learn how to use HttpURLConnection in a Java program to send GET and POST requests and then print the response.

Prerequisites

For this HttpURLConnection example, you should have completed the Spring MVC Tutorial because it has URLs for GET and POST HTTP methods.

Consider deploying to a localhost Tomcat server.

SpringMVCExample Summary

Java HTTP GET Request

localhost:8080/SpringMVCExample/

Java HTTP GET Request for Login Page

localhost:8080/SpringMVCExample/login

Java HTTP POST Request

localhost:8080/SpringMVCExample?userName=Pankaj
localhost:8080/SpringMVCExample/login?userName=Pankaj&pwd=apple123 - for multiple params

Deriving parameters from the form

The HTML of the login page contains the following form:

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "https://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Login Page</title>
</head>
<body>
<form action="home" method="post">
<input type="text" name="userName"><br>
<input type="submit" value="Login">
</form>
</body>
</html>

The method is POST.
The action is home.
- localhost:8080/SpringMVCExample/home
userName is of type text.

You can construct a POST request to:

localhost:8080/SpringMVCExample/home?userName=Pankaj

This will serve as the basis for the HttpURLConnection example.

`HttpURLConnection` Example

Here are the steps for sending Java HTTP requests using HttpURLConnection class:

Create a URL object from the GET or POST URL String.
Call the openConnection() method on the URL object that returns an instance of HttpURLConnection.
Set the request method in HttpURLConnection instance (default value is GET).
Call setRequestProperty() method on HttpURLConnection instance to set request header values (such as "User-Agent", "Accept-Language", etc).
We can call getResponseCode() to get the response HTTP code. This way, we know if the request was processed successfully or if there was any HTTP error message thrown.
For GET, use Reader and InputStream to read the response and process it accordingly.
For POST, before the code handles the response, it needs to get the OutputStream from the HttpURLConnection instance and write POST parameters into it.

Here is an example program that uses HttpURLConnection to send Java GET and POST requests:

HttpURLConnectionExample.java

package com.journaldev.utils;

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

public class HttpURLConnectionExample {

	private static final String USER_AGENT = "Mozilla/5.0";

	private static final String GET_URL = "https://localhost:9090/SpringMVCExample";

	private static final String POST_URL = "https://localhost:9090/SpringMVCExample/home";

	private static final String POST_PARAMS = "userName=Pankaj";

	public static void main(String[] args) throws IOException {
		sendGET();
		System.out.println("GET DONE");
		sendPOST();
		System.out.println("POST DONE");
	}

	private static void sendGET() throws IOException {
		URL obj = new URL(GET_URL);
		HttpURLConnection con = (HttpURLConnection) obj.openConnection();
		con.setRequestMethod("GET");
		con.setRequestProperty("User-Agent", USER_AGENT);
		int responseCode = con.getResponseCode();
		System.out.println("GET Response Code :: " + responseCode);
		if (responseCode == HttpURLConnection.HTTP_OK) { // success
			BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
			String inputLine;
			StringBuffer response = new StringBuffer();

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

			// print result
			System.out.println(response.toString());
		} else {
			System.out.println("GET request did not work.");
		}

	}

	private static void sendPOST() throws IOException {
		URL obj = new URL(POST_URL);
		HttpURLConnection con = (HttpURLConnection) obj.openConnection();
		con.setRequestMethod("POST");
		con.setRequestProperty("User-Agent", USER_AGENT);

		// For POST only - START
		con.setDoOutput(true);
		OutputStream os = con.getOutputStream();
		os.write(POST_PARAMS.getBytes());
		os.flush();
		os.close();
		// For POST only - END

		int responseCode = con.getResponseCode();
		System.out.println("POST Response Code :: " + responseCode);

		if (responseCode == HttpURLConnection.HTTP_OK) { //success
			BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
			String inputLine;
			StringBuffer response = new StringBuffer();

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

			// print result
			System.out.println(response.toString());
		} else {
			System.out.println("POST request did not work.");
		}
	}

}

Compile and run the code. It will produce the following output:

OutputGET Response Code :: 200
<html><head>	<title>Home</title></head><body><h1>	Hello world!  </h1><P>  The time on the server is March 6, 2015 9:31:04 PM IST. </P></body></html>
GET DONE
POST Response Code :: 200
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "https://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>User Home Page</title></head><body><h3>Hi Pankaj</h3></body></html>
POST DONE

Compare this output to the browser HTTP response.

If you have to send GET and POST requests over HTTPS protocol, then you need to use javax.net.ssl.HttpsURLConnection instead of java.net.HttpURLConnection. HttpsURLConnection will handle the SSL handshake and encryption.

Conclusion

In this article, you learned how to use HttpURLConnection in a Java program to send GET and POST requests and then print the response.

Continue your learning with more Java tutorials.

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About the author(s)

Pankaj Kumar

Author

See author profile

Java and Python Developer for 20+ years, Open Source Enthusiast, Founder of https://www.askpython.com/, https://www.linuxfordevices.com/, and JournalDev.com (acquired by DigitalOcean). Passionate about writing technical articles and sharing knowledge with others. Love Java, Python, Unix and related technologies. Follow my X @PankajWebDev

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Bradley Kouchi

Editor

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Category:

Tutorial

Tags:

Java

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Was this helpful?

JournalDev

July 6, 2015

Hi, I wast tried to hit an end point which is get to fetch the detail using apache http, the json response that I get has got some attributes which are empty array. But the same end point I hit thru a browser or a rest client I don’t see these attributes as part of json response. Why is that ?

- abhineet

JournalDev

September 25, 2015

Thanks man! This really worked as expected. Good job (y)

- Gurgen

JournalDev

November 29, 2015

Nice tutorial. Well I didn’t get on thing. `os.write(POST_PARAMS.getBytes()); os.flush(); os.close();` How can I print my complete POST URL, after adding parameters. Is that possible to output the URL?

- akshay

JournalDev

December 8, 2015

This tutorial is great and clear. But how about 2 parameters?

- mbrean

JournalDev

December 16, 2015

Thanks :D

- Rinaldes Duma

JournalDev

February 16, 2016

hello am getting error : javax.net.ssl.SSLHandshakeException: Remote host closed connection during handshake. I did same as above except for https connection. please help.

- KIRAN

JournalDev

April 4, 2016

Many thanks - I’ve been puzzling over how to POST from a Spring Controller and your article was a great help. Andrew (Sheffield UK)

- Andrew

JournalDev

June 7, 2016

is there any way to get request url from browser console

- suman

JournalDev

June 23, 2016

I have to say I’m new to Java but have worked with C, C++ , python and several other languages. Java was the hardest for me to understand and work with but this little tutorial made it very plain how to use the java.net module the way I wanted. Very Nice Job!

- Mathew Eickmeyer

JournalDev

November 8, 2016

Really awesome tutorials so easy to understand. Thanks pankaj.

- Nidh