urlconnectiontest.java

Java经典教程core java

/**
   version 1.10 2004-08-04
   author Cay Horstmann
*/

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

/**
   This program connects to an URL and displays the 
   response header data and the first 10 lines of the
   requested data. 

   Supply the URL and an optional username and password (for
   HTTP basic authentication) on the command line.
*/
public class URLConnectionTest
{  
   public static void main(String[] args)
   {  
      try
      {  
         String urlName;
         if (args.length > 0)
            urlName = args[0];
         else
            urlName = "http://java.sun.com";

         URL url = new URL(urlName);
         URLConnection connection = url.openConnection();

         // set username, password if specified on command line

         if (args.length > 2)
         {  
            String username = args[1];
            String password = args[2];
            String input = username + ":" + password;
            String encoding = base64Encode(input);
            connection.setRequestProperty("Authorization", "Basic " + encoding);
         }

         connection.connect();

         // print header fields

         Map<String, List<String>> headers = connection.getHeaderFields();
         for (Map.Entry<String, List<String>> entry : headers.entrySet())
         {
            String key = entry.getKey();
            for (String value : entry.getValue())
               System.out.println(key + ": " + value);
         }

         // print convenience functions

         System.out.println("----------");
         System.out.println("getContentType: " + connection.getContentType());
         System.out.println("getContentLength: " + connection.getContentLength());
         System.out.println("getContentEncoding: " + connection.getContentEncoding());
         System.out.println("getDate: " + connection.getDate());
         System.out.println("getExpiration: " + connection.getExpiration());
         System.out.println("getLastModifed: " + connection.getLastModified());
         System.out.println("----------");

         Scanner in = new Scanner(connection.getInputStream());

         // print first ten lines of contents

         for (int n = 1; in.hasNextLine() && n <= 10; n++)
            System.out.println(in.nextLine());
         if (in.hasNextLine()) System.out.println(". . .");
      }
      catch (IOException e)
      {  
         e.printStackTrace();
      }
   }

   /**
      Computes the Base64 encoding of a string
      @param s a string
      @return the Base 64 encoding of s
   */
   public static String base64Encode(String s)
   {  
      ByteArrayOutputStream bOut = new ByteArrayOutputStream();
      Base64OutputStream out = new Base64OutputStream(bOut);
      try
      {  
         out.write(s.getBytes());
         out.flush();
      }
      catch (IOException e)
      {
      }
      return bOut.toString();
   }
}

/**
   This stream filter converts a stream of bytes to their
   Base64 encoding.

   Base64 encoding encodes 3 bytes into 4 characters.
   |11111122|22223333|33444444|
   Each set of 6 bits is encoded according to the
   toBase64 map. If the number of input bytes is not
   a multiple of 3, then the last group of 4 characters
   is padded with one or two = signs. Each output line
   is at most 76 characters.
*/
class Base64OutputStream extends FilterOutputStream
{
   /**
      Constructs the stream filter
      @param out the stream to filter
   */
   public Base64OutputStream(OutputStream out)
   {  
      super(out);
   }

   public void write(int c) throws IOException
   {  
      inbuf[i] = c;
      i++;
      if (i == 3)
      {  
         super.write(toBase64[(inbuf[0] & 0xFC) >> 2]);
         super.write(toBase64[((inbuf[0] & 0x03) << 4) | ((inbuf[1] & 0xF0) >> 4)]);
         super.write(toBase64[((inbuf[1] & 0x0F) << 2) | ((inbuf[2] & 0xC0) >> 6)]);
         super.write(toBase64[inbuf[2] & 0x3F]);
         col += 4;
         i = 0;
         if (col >= 76)
         {  
            super.write('\n');
            col = 0;
         }
      }
   }

   public void flush() throws IOException
   {  
      if (i == 1)
      {  
         super.write(toBase64[(inbuf[0] & 0xFC) >> 2]);
         super.write(toBase64[(inbuf[0] & 0x03) << 4]);
         super.write('=');
         super.write('=');
      }
      else if (i == 2)
      {  
         super.write(toBase64[(inbuf[0] & 0xFC) >> 2]);
         super.write(toBase64[((inbuf[0] & 0x03) << 4) | ((inbuf[1] & 0xF0) >> 4)]);
         super.write(toBase64[(inbuf[1] & 0x0F) << 2]);
         super.write('=');
      }
   }

   private static char[] toBase64 =
   {  
      'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
      'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
      'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
      'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'
   };

   private int col = 0;
   private int i = 0;
   private int[] inbuf = new int[3];
}