How to send HTTP request in java? [duplicate]

Answer 1

Here's a complete Java 7 program:

class GETHTTPResource {
  public static void main(String[] args) throws Exception {
    try (java.util.Scanner s = new java.util.Scanner(new java.net.URL("http://tools.ietf.org/rfc/rfc768.txt").openStream())) {
      System.out.println(s.useDelimiter("\\A").next());
    }
  }
}

The new try-with-resources will auto-close the Scanner, which will auto-close the InputStream.

Answer 2

You may use Socket for this like

String host = "www.yourhost.com";
Socket socket = new Socket(host, 80);
String request = "GET / HTTP/1.0\r\n\r\n";
OutputStream os = socket.getOutputStream();
os.write(request.getBytes());
os.flush();

InputStream is = socket.getInputStream();
int ch;
while( (ch=is.read())!= -1)
    System.out.print((char)ch);
socket.close();    

Answer 3

There's a great link about sending a POST request here by Example Depot::

try {
    // Construct data
    String data = URLEncoder.encode("key1", "UTF-8") + "=" + URLEncoder.encode("value1", "UTF-8");
    data += "&" + URLEncoder.encode("key2", "UTF-8") + "=" + URLEncoder.encode("value2", "UTF-8");

    // Send data
    URL url = new URL("http://hostname:80/cgi");
    URLConnection conn = url.openConnection();
    conn.setDoOutput(true);
    OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream());
    wr.write(data);
    wr.flush();

    // Get the response
    BufferedReader rd = new BufferedReader(new InputStreamReader(conn.getInputStream()));
    String line;
    while ((line = rd.readLine()) != null) {
        // Process line...
    }
    wr.close();
    rd.close();
} catch (Exception e) {
}

If you want to send a GET request you can modify the code slightly to suit your needs. Specifically you have to add the parameters inside the constructor of the URL. Then, also comment out this wr.write(data);

One thing that's not written and you should beware of, is the timeouts. Especially if you want to use it in WebServices you have to set timeouts, otherwise the above code will wait indefinitely or for a very long time at least and it's something presumably you don't want.

Timeouts are set like this conn.setReadTimeout(2000); the input parameter is in milliseconds