How do I do a HTTP GET in Java?

Question

Hello,

How do I do a HTTP GET in Java?

Thanks.

David

Answer 1

Technically you could do it with a straight TCP socket. I wouldn't recommend it however. I would highly recommend you use Apache HttpClient instead. In it's simplest form:

GetMethod get = new GetMethod("http://httpcomponents.apache.org");
// execute method and handle any error responses.
...
InputStream in = get.getResponseBodyAsStream();
// Process the data from the input stream.
get.releaseConnection();

and here is a more complete example.

Answer 2

If you want to stream any webpage, you can use the method below.

import java.io.*;
import java.net.*;

public class c {

   public String getHTML(String urlToRead) {
      URL url;
      HttpURLConnection conn;
      BufferedReader rd;
      String line;
      String result = "";
      try {
         url = new URL(urlToRead);
         conn = (HttpURLConnection) url.openConnection();
         conn.setRequestMethod("GET");
         rd = new BufferedReader(new InputStreamReader(conn.getInputStream()));
         while ((line = rd.readLine()) != null) {
            result += line;
         }
         rd.close();
      } catch (Exception e) {
         e.printStackTrace();
      }
      return result;
   }

   public static void main(String args[])
   {
     c c = new c();
     System.out.println(c.getHTML(args[0]));
   }
}

Answer 3

The simplest way that doesn't require third party libraries it to create a URL object and then call either openConnection or openStream on it. Note that this is a pretty basic API, so you won't have a lot of control over the headers.

Answer 4

If you dont want to use external libraries, you can use URL and URLConnection classes from standard Java API.

An example looks like this:

urlString = "http://wherever.com/someAction?param1=value1&param2=value2....";
URL url = new URL(urlString);
URLConnection conn = url.openConnection();
InputStream is = conn.getInputStream() 
// Do what you want with that stream