HttpURLConnection.java

// HttpURLConnection.java - Subclass of communications links using
//			Hypertext Transfer Protocol.

/* Copyright (C) 1998, 1999, 2000, 2002 Free Software Foundation

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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WITHOUT ANY WARRANTY; without even the implied warranty of
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General Public License for more details.

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Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. 

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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permission to link this library with independent modules to produce an
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terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
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package java.net;

import java.io.*;
import java.security.Permission;

/*
 * Written using on-line Java Platform 1.2 API Specification, as well
 * as "The Java Class Libraries", 2nd edition (Addison-Wesley, 1998).
 * Status:  Believed complete and correct.
 */

/**
 * This class provides a common abstract implementation for those 
 * URL connection classes that will connect using the HTTP protocol.
 * In addition to the functionality provided by the URLConnection
 * class, it defines constants for HTTP return code values and
 * methods for setting the HTTP request method and determining whether
 * or not to follow redirects. 
 *
 * @since 1.1
 *
 * @author Warren Levy (warrenl@cygnus.com)
 * @author Aaron M. Renn (arenn@urbanophile.com)
 */
public abstract class HttpURLConnection extends URLConnection
{
  /* HTTP Success Response Codes */

  /**
   * Indicates that the client may continue with its request.  This value
   * is specified as part of RFC 2068 but was not included in Sun's JDK, so
   * beware of using this value
   */
  static final int HTTP_CONTINUE = 100;
  
  /**
   * Indicates the request succeeded.
   */
  public static final int HTTP_OK		= 200;

  /**
   * The requested resource has been created.
   */
  public static final int HTTP_CREATED		= 201;

  /**
   * The request has been accepted for processing but has not completed.
   * There is no guarantee that the requested action will actually ever
   * be completed succesfully, but everything is ok so far.
   */
  public static final int HTTP_ACCEPTED 	= 202;

  /**
   * The meta-information returned in the header is not the actual data
   * from the original server, but may be from a local or other copy. 
   * Normally this still indicates a successful completion.
   */
  public static final int HTTP_NOT_AUTHORITATIVE = 203;

  /**
   * The server performed the request, but there is no data to send
   * back.  This indicates that the user's display should not be changed.
   */
  public static final int HTTP_NO_CONTENT	= 204;

  /**
   * The server performed the request, but there is no data to sent back,
   * however, the user's display should be "reset" to clear out any form
   * fields entered.
   */
  public static final int HTTP_RESET		= 205;

  /**
   * The server completed the partial GET request for the resource.
   */
  public static final int HTTP_PARTIAL		= 206;


  /* HTTP Redirection Response Codes */

  /**
   * There is a list of choices available for the requested resource.
   */
  public static final int HTTP_MULT_CHOICE = 300;
  
  /**
   * The resource has been permanently moved to a new location.
   */
  public static final int HTTP_MOVED_PERM = 301;
  
  /**
   * The resource requested has been temporarily moved to a new location.
   */
  public static final int HTTP_MOVED_TEMP = 302;
  
  /**
   * The response to the request issued is available at another location.
   */
  public static final int HTTP_SEE_OTHER = 303;
  
  /**
   * The document has not been modified since the criteria specified in
   * a conditional GET.
   */
  public static final int HTTP_NOT_MODIFIED = 304;
  
  
  /* HTTP Client Error Response Codes */

  /**
   * The request was misformed or could not be understood.
   */
  public static final int HTTP_BAD_REQUEST = 400;
  
  /**
   * The request made requires user authorization.  Try again with
   * a correct authentication header.
   */
  public static final int HTTP_UNAUTHORIZED = 401;
  
  /**
   * Code reserved for future use - I hope way in the future.
   */
  public static final int HTTP_PAYMENT_REQUIRED = 402;
  
  /**
   * There is no permission to access the requested resource.
   */
  public static final int HTTP_FORBIDDEN = 403;
  
  /**
   * The requested resource was not found.
   */
  public static final int HTTP_NOT_FOUND = 404;
  
  /**
   * The specified request method is not allowed for this resource.
   */
  public static final int HTTP_BAD_METHOD = 405;
  
  /**
   * Based on the input headers sent, the resource returned in response
   * to the request would not be acceptable to the client.
   */
  public static final int HTTP_NOT_ACCEPTABLE = 406;
  
  /**
   * The client must authenticate with a proxy prior to attempting this
   * request.
   */
  public static final int HTTP_PROXY_AUTH = 407;
  
  /**
   * The request timed out.
   */
  public static final int HTTP_CLIENT_TIMEOUT = 408;
  
  /**
   * There is a conflict between the current state of the resource and the
   * requested action.
   */
  public static final int HTTP_CONFLICT = 409;
  
  /**
   * The requested resource is no longer available.  This ususally indicates
   * a permanent condition.
   */
  public static final int HTTP_GONE = 410;

  /**
   * A Content-Length header is required for this request, but was not
   * supplied.
   */
  public static final int HTTP_LENGTH_REQUIRED = 411;
  
  /**
   * A client specified pre-condition was not met on the server.
   */
  public static final int HTTP_PRECON_FAILED = 412;
  
  /**
   * The request sent was too large for the server to handle.
   */
  public static final int HTTP_ENTITY_TOO_LARGE = 413;
  
  /**
   * The name of the resource specified was too long.
   */
  public static final int HTTP_REQ_TOO_LONG = 414;
  
  /**
   * The request is in a format not supported by the requested resource.
   */
  public static final int HTTP_UNSUPPORTED_TYPE = 415;


  /* HTTP Server Error Response Codes */

  /**
   * This error code indicates that some sort of server error occurred.
   */
  public static final int HTTP_SERVER_ERROR    = 500;

  /**
   * The server encountered an unexpected error (such as a CGI script crash)
   * that prevents the request from being fulfilled.
   */
  public static final int HTTP_INTERNAL_ERROR   = 500;

  /**
   * The server does not support the requested functionality.  
   * @since 1.3
   */
  static final int HTTP_NOT_IMPLEMENTED = 501;

  /**
   * The proxy encountered a bad response from the server it was proxy-ing for
   */
  public static final int HTTP_BAD_GATEWAY = 502;

  /**
   * The HTTP service is not availalble, such as because it is overloaded
   * and does not want additional requests.
   */
  public static final int HTTP_UNAVAILABLE = 503;

  /**
   * The proxy timed out getting a reply from the remote server it was
   * proxy-ing for.
   */
  public static final int HTTP_GATEWAY_TIMEOUT = 504;

  /**
   * This server does not support the protocol version requested.
   */
  public static final int HTTP_VERSION = 505;

  // Non-HTTP response static variables

  /**
   * Flag to indicate whether or not redirects should be automatically
   * followed by default.
   */
  private static boolean followRedirects = true;

  /**
   * This is a list of valid request methods, separated by "|" characters.
   */
  private static String valid_methods
      = "|GET|POST|HEAD|OPTIONS|PUT|DELETE|TRACE|";

  // Instance Variables

  /**
   * The requested method in use for this connection. Default is GET.
   */
  protected String method = "GET";

  /**
   * The response code received from the server
   */
  protected int responseCode = -1;

  /**
   * The response message string received from the server.
   */
  protected String responseMessage = null;

  /**
   * If this instance should follow redirect requests.
   */
  protected boolean instanceFollowRedirects = followRedirects;

  /**
   * Whether we alreadt got a valid response code for this connection.
   * Used by <code>getResponceCode()</code> and
   * <code>getResponseMessage()</code>.
   */
  private boolean gotResponseVals = false;

  /**
   * Create an HttpURLConnection for the specified URL
   *
   * @param url The URL to create this connection for.
   */
  protected HttpURLConnection(URL url)
  {
    super(url);
  }
  
  /**   
   * Closes the connection to the server.
   */
  public abstract void disconnect();

  /** 
   * Returns a boolean indicating whether or not this connection is going
   * through a proxy
   * 
   * @return true if through a proxy, false otherwise
   */
  public abstract boolean usingProxy();

  /**
   * Sets whether HTTP redirects (requests with response code 3xx) should be
   * automatically followed by this class. True by default
   *
   * @param set true if redirects should be followed, false otherwis.
   *
   * @exception SecurityException If a security manager exists and its
   * checkSetFactory method doesn't allow the operation
   */
  public static void setFollowRedirects(boolean set)
  {
    // Throw an exception if an extant security mgr precludes
    // setting the factory.
    SecurityManager s = System.getSecurityManager();
    if (s != null)
      s.checkSetFactory();

    followRedirects = set;
  }

  /**
   * Returns a boolean indicating whether or not HTTP redirects will 
   * automatically be followed or not.
   *
   * @return true if redirects will be followed, false otherwise
   */
  public static boolean getFollowRedirects()
  {
    return followRedirects;
  }

  /**
   * Returns the value of this HttpURLConnection's instanceFollowRedirects
   * field
   */
  public boolean getInstanceFollowRedirects ()
  {
    return instanceFollowRedirects;
  }

  /**
   * Sets the value of this HttpURLConnection's instanceFollowRedirects field
   */
  public void setInstanceFollowRedirects (boolean follow)
  {
    instanceFollowRedirects = follow;
  }

  /**
   * Set the method for the URL request, one of:
   * GET POST HEAD OPTIONS PUT DELETE TRACE are legal
   *
   * @exception ProtocolException If the method cannot be reset or if the
   * requested method isn't valid for HTTP
   */
  public void setRequestMethod(String method) throws ProtocolException
  {
    if (connected)
      throw new ProtocolException("Already connected");

    method = method.toUpperCase();
    if (valid_methods.indexOf("|" + method + "|") != -1)
      this.method = method;
    else
      throw new ProtocolException("Invalid HTTP request method: " + method);

  }

  /**
   * The request method currently in use for this connection.
   *
   * @return The request method
   */
  public String getRequestMethod()
  {
    return method;
  }

  /**
   * Gets the status code from an HTTP response message, or -1 if
   * the response code could not be determined.
   * Note that all valid response codes have class variables
   * defined for them in this class.
   *
   * @return The response code
   *
   * @exception IOException If an error occurs
   */
  public int getResponseCode() throws IOException
  {
    if (!gotResponseVals)
      getResponseVals();
    return responseCode;
  }

  /**
   * Gets the HTTP response message, if any, returned along with the
   * response code from a server. Null if no response message was set
   * or an error occured while connecting.
   *
   * @return The response message
   *
   * @exception IOException If an error occurs
   */
  public String getResponseMessage() throws IOException
  {
    if (!gotResponseVals)
      getResponseVals();
    return responseMessage;
  }

  private void getResponseVals() throws IOException
  {
    // getHeaderField() will connect for us, but do it here first in
    // order to pick up IOExceptions.
    if (!connected)
      connect();
      
    gotResponseVals = true;
    // Response is the first header received from the connection.
    String respField = getHeaderField(0);
    
    if (respField == null || ! respField.startsWith("HTTP/"))
      {
	// Set to default values on failure.
        responseCode = -1;
	responseMessage = null;
	return;
      }

    int firstSpc, nextSpc;
    firstSpc = respField.indexOf(' ');
    nextSpc = respField.indexOf(' ', firstSpc + 1);
    responseMessage = respField.substring(nextSpc + 1);
    String codeStr = respField.substring(firstSpc + 1, nextSpc);
    try
      {
	responseCode = Integer.parseInt(codeStr);
      }
    catch (NumberFormatException e)
      {
	// Set to default values on failure.
        responseCode = -1;
	responseMessage = null;
      }
  }

  /**
   * Returns a permission object representing the permission necessary to make
   * the connection represented by this object
   *
   * @exception IOException If an error occurs
   */
  public Permission getPermission() throws IOException
  {
    URL url = getURL();
    String host = url.getHost();
    int port = url.getPort();
    if (port == -1)
      port = 80;
    
    host = host + ":" + port;
    
    return new SocketPermission(host, "connect");
  }

  /**
   * This method allows the caller to retrieve any data that might have
   * been sent despite the fact that an error occurred.  For example, the
   * HTML page sent along with a 404 File Not Found error.  If the socket
   * is not connected, or if no error occurred or no data was returned,
   * this method returns <code>null</code>.
   *
   * @return An <code>InputStream</code> for reading error data.
   */
  public InputStream getErrorStream ()
  {
    if (!connected)
      return(null);
    
    int code;
    try 
      {
	code = getResponseCode();
      }
    catch(IOException e)
      {
	code = -1;
      }
    
    if (code == -1)
      return(null);
    
    if (((code/100) != 4) || ((code/100) != 5))
      return(null); 
    
    try
      {
	PushbackInputStream pbis = new PushbackInputStream(getInputStream());
	
	int i = pbis.read();
	if (i == -1)
	  return(null);
	
	pbis.unread(i);
	return(pbis);
      }
    catch(IOException e)
      {
	return(null);
      }
  }

  /**
   * Returns the value of the named field parsed as date
   */
  public long getHeaderFieldDate (String key, long value)
  {
    // FIXME: implement this correctly
    // http://www.w3.org/Protocols/HTTP-NG/ng-notes.txt
    
    return super.getHeaderFieldDate (key, value);
  }
}