usinghttpurlconnection.java

Java网络编程与分布式计算, 主要分析java网络各方面的编程, 提供许多实用安全

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

// Chapter 9, Listing 5
public class UsingHttpURLConnection
{
	public static void main(String args[]) throws Exception
	{
		int argc = args.length;

		// Check for valid number of parameters
		if (argc != 1)
		{
			System.out.println ("Syntax :");
			System.out.println ("java UsingHttpURLConnection url");
			return;
		}
	
		// Catch any thrown exceptions
		try
		{
			// Create an instance of java.net.URL
			java.net.URL myURL = new URL ( args[0] );

			// Create a URLConnection object, for this URL
			// NOTE : no connection has yet been established
			URLConnection connection = myURL.openConnection();

			// Check to see if connection is a HttpURLConnection instance
			if (connection instanceof java.net.HttpURLConnection)
			{
				// Yes... cast to a HttpURLConnection instance
				HttpURLConnection hConnection = (HttpURLConnection) connection;

				// Disable automatic redirection, to see the status header
				hConnection.setFollowRedirects(false);

				// Connect to server
				hConnection.connect();

				// Check to see if a proxy server is being used
				if (hConnection.usingProxy())
				{
					System.out.println ("Proxy server used to access resource");
				}
				else
				{
					System.out.println ("No proxy server used to access resource");
				}


				// Get the status code
				int   code = hConnection.getResponseCode();

				// Get the status message
				String msg = hConnection.getResponseMessage();

				// If a 'normal' response
				if ( code == HttpURLConnection.HTTP_OK )
				{
					// Notify user
					System.out.println ("Normal response returned : " +
						code + " " + msg );
				}
				else
				{
					// Output status code and message
					System.out.println ("Abnormal response returned : " 
						+ code + " " + msg );
				}

				// Pause for user
				System.out.println ("Hit enter to continue");
				System.in.read();
			}
			else
			{
				System.err.println ("Invalid transport protocol - not http!");
				return;
			}
		}
		// MalformedURLException indicates parsing error
		catch (MalformedURLException mue)
		{
			System.err.println ("Unable to parse URL!");
			return;
		}
		// IOException indicates network or I/O error
		catch (IOException ioe)
		{
			System.err.println ("I/O Error : " + ioe);
			return;
		}
	}
}