urlconnectiontest.java

char44-4 URL连接测试 提供了本书第4章的URL连接测试实例的源程序

//URLConnectionTest.java
import java.io.*;
import java.net.*;
import java.util.*;
/**
此程序连接到一个URL地址，并打印出所请求的信息的前10行
*/
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();
			// 设置用户名和密码
			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();
			
			// 打印出头文件
			
			int n = 1;
			String key;
			while ((key = connection.getHeaderFieldKey(n)) != null)
			{
				String value = connection.getHeaderField(n);
				System.out.println(key + ": " + value);
				n++;
			}
			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("----------");
			
			
			BufferedReader in = new BufferedReader(new
				InputStreamReader(connection.getInputStream()));
			
			// 打印出前10行内容
			
			String line;
			n = 1;
			while ((line = in.readLine()) != null && n <= 10)
			{
				System.out.println(line);
				n++;
			}
			if (line != null) System.out.println(". . .");
        }
		catch (IOException exception)
		{
			exception.printStackTrace();
		}
	}
	
	/**
	计算通过 Base64 编码的字符串
	*/
	public static String base64Encode(String s)
	{
		ByteArrayOutputStream bOut
			= new ByteArrayOutputStream();
		Base64OutputStream out = new Base64OutputStream(bOut);
		try
		{
			out.write(s.getBytes());
			out.flush();
		}
		catch (IOException exception)
		{
		}
		return bOut.toString();
	}
}

/**
这个流过滤器将流转变为Base64编码的形式  
  Base64 编码将3个字节转换为4个字符
*/
  class Base64OutputStream extends FilterOutputStream
  {
  /**
构建流过滤器
	*/
	  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];
}