HttpURLConnection class from java.net package can be used to send Java HTTP Request programmatically. Today we will learn how to use HttpURLConnection in java program to send GET and POST requests and then print the response.
Java HTTP Request
For our HttpURLConnection example, I am using sample project from Spring MVC Tutorial because it has URLs for GET and POST HTTP methods. Below are the images for this web application, I have deployed it on my localhost tomcat server.
Java HTTP GET Request
Java HTTP GET Request for Login Page
Java HTTP POST Request
For Java HTTP GET requests, we have all the information in the browser URL itself. So from above images, we know that we have following GET requests URL.
- http://localhost:9090/SpringMVCExample/
- http://localhost:9090/SpringMVCExample/login
Above URL’s don’t have any parameters but as we know that in HTTP GET requests parameters are part of URL itself, so for example if we have to send a parameter named userName with value as Pankaj then the URLs would have been like below.
- http://localhost:9090/SpringMVCExample?userName=Pankaj
- http://localhost:9090/SpringMVCExample/login?userName=Pankaj&pwd=apple123 – for multiple params
If we know the POST URL and what parameters it’s expecting, it’s awesome but in this case we will figure it out from the login form source.
Below is the HTML code we get when we view source of the login page in any of the browser.
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://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>
Look at the form method in the source, as expected it’s POST. Now see that action is “home”, so the POST URL would be http://localhost:9090/SpringMVCExample/home. Now check the different elements in the form, from above form we can deduce that we need to send one POST parameter with name userName and it’s of type String.
So now we have complete details of GET and POST requests and we can proceed for the Java HTTP Request example program.
Below are the steps we need to follow for sending Java HTTP requests using HttpURLConnection class.
- Create
URLobject from the GET/POST URL String. - Call openConnection() method on URL object that returns instance of
HttpURLConnection - Set the request method in
HttpURLConnectioninstance, default value is GET. - Call setRequestProperty() method on
HttpURLConnectioninstance to set request header values, such as “User-Agent” and “Accept-Language” etc. - We can call
getResponseCode()to get the response HTTP code. This way we know if the request was processed successfully or there was any HTTP error message thrown. - For GET, we can simply use Reader and InputStream to read the response and process it accordingly.
- For POST, before we read response we need to get the OutputStream from
HttpURLConnectioninstance and write POST parameters into it.
HttpURLConnection Example
Based on the above steps, below is the example program showing usage of HttpURLConnection to send Java GET and POST requests.
HttpURLConnectionExample.java code:
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 = "http://localhost:9090/SpringMVCExample";
private static final String POST_URL = "http://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 not worked");
}
}
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 not worked");
}
}
}
When we execute above program, we get below response.
GET 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" "http://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
Just compare it with the browser HTTP response and you will see that it’s same. You can also save response into any HTML file and open it to compare the responses visually.
Quick Tip: If you have to send GET/POST requests over HTTPS protocol, then all you need is to use javax.net.ssl.HttpsURLConnection instead of java.net.HttpURLConnection. Rest all the steps will be same as above, HttpsURLConnection will take care of SSL handshake and encryption.
Greshma John says
Hi ,
I am getting the following error for post request
Exception in thread “main” java.io.IOException: Unable to tunnel through proxy. Proxy returns “HTTP/1.1 400 Bad Request” .
I have added extra proxy settings in the sendPOST() method .
Kristina Mendoza says
Thanks for the informative post! I’m still a newbie when it comes to programming using Java programming language but reading posts like this really helps me understand it even more. Cheers!
Mahadev says
Hai, how much it will take to get a response once we hit the url??
Deepak says
Hi
I am using httpsurlconnection.
Url: “https://localhost:8443/LoginApp”
+ “/restservice/agentchildservice/getAttributesForIdentity”;
connection.respose is 200. Its a post call. But the values are not getting fetched , its showing me the login page html content.
BufferedReader br = new BufferedReader(new InputStreamReader((conn.getInputStream())));
StringBuilder sb = new StringBuilder();
String output;
while ((output = br.readLine()) != null) {
sb.append(output);
}
System.out.println(sb);
on printing it will give me the login page html in stringbuilder variable.
I want to get the values. Can you please suggest.
kiran says
Hi Pankaj,
I have an end point url, and i tried through the SOUP UI using REST its giving expected response.
Now i need to implement through java code and test wether i am getting expected response.
can you help on this please. For the first time i am working on web services.
would like to in detail, will be required any jars in eclipse/project etc.
Thanks,
Kiran
kiran says
I have request xml for this as well. how to include while calling web service.
Samas says
Connection exceptioni s coming when I run the java code. Will you please help me to use the code. Is it to run the java code and automatically the code runs?
Vandens says
Awesome…. I have changed POST_PARAMS into custom xml data in string and it works!
Thanks you.
naresh says
hi sir..
output::
GET Response Code :: 200
Home Hello world! The time on the server is March 6, 2015 9:31:04 PM IST.
GET DONE
POST Response Code :: 200
User Home PageHi Pankaj
POST DONE
how to display in web page sir ….
every time copy paste in browser cannot possible sir … i mean direct when run the programe out put will be display in web page sir
same like above pages
thanks sir
Nidh says
Really awesome tutorials so easy to understand. Thanks pankaj.
Mathew Eickmeyer says
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!
suman says
is there any way to get request url from browser console
Andrew says
Many thanks – I’ve been puzzling over how to POST from a Spring Controller and your article was a great help.
Andrew (Sheffield UK)
Pankaj says
Thanks Andrew, I hope you will find my other articles useful too. 🙂
naresh says
can you give your mail id
KIRAN says
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.
Pankaj says
Did you used
Rinaldes Duma says
Thanks 😀
Pankaj says
you are welcome.
mbrean says
This tutorial is great and clear. But how about 2 parameters?
Mostafa Anter Sayd says
String params = “name=mostafa&age=22”;
u r welcome
Pankaj says
Thanks for answering the question Mostafa.
akshay says
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?
Pankaj says
POST parameters are not part of URL, so you see them in URL or print them.
Gurgen says
Thanks man! This really worked as expected. Good job (y)
Pankaj says
You are welcome Gurgen.
abhineet says
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 ?
Pankaj says
It may be because the browser/rest client is not displaying them. Can you try through Chrome Postman or similar kind of tool and check the raw response?
You can also print the response at the server side before sending it to confirm this.