url.java

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/*
 * @(#)URL.java	1.108 06/10/10
 *
 * Copyright  1990-2008 Sun Microsystems, Inc. All Rights Reserved.  
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER  
 *   
 * This program is free software; you can redistribute it and/or  
 * modify it under the terms of the GNU General Public License version  
 * 2 only, as published by the Free Software Foundation.   
 *   
 * This program is distributed in the hope that it will be useful, but  
 * WITHOUT ANY WARRANTY; without even the implied warranty of  
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU  
 * General Public License version 2 for more details (a copy is  
 * included at /legal/license.txt).   
 *   
 * You should have received a copy of the GNU General Public License  
 * version 2 along with this work; if not, write to the Free Software  
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  
 * 02110-1301 USA   
 *   
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa  
 * Clara, CA 95054 or visit www.sun.com if you need additional  
 * information or have any questions. 
 *
 */

package java.net;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Hashtable;
import java.util.StringTokenizer;
import sun.security.util.SecurityConstants;

/**
 * Class <code>URL</code> represents a Uniform Resource
 * Locator, a pointer to a "resource" on the World
 * Wide Web. A resource can be something as simple as a file or a
 * directory, or it can be a reference to a more complicated object,
 * such as a query to a database or to a search engine. More
 * information on the types of URLs and their formats can be found at:
 * <blockquote>
 *     <a href="http://archive.ncsa.uiuc.edu/SDG/Software/Mosaic/Demo/url-primer.html">
 *    <i>http://archive.ncsa.uiuc.edu/SDG/Software/Mosaic/Demo/url-primer.html</i></a>
 * </blockquote>
 * <p>
 * In general, a URL can be broken into several parts. The previous
 * example of a URL indicates that the protocol to use is
 * <code>http</code> (HyperText Transfer Protocol) and that the
 * information resides on a host machine named
 * <code>www.ncsa.uiuc.edu</code>. The information on that host
 * machine is named <code>/SDG/Software/Mosaic/Demo/url-primer.html</code>. The exact
 * meaning of this name on the host machine is both protocol
 * dependent and host dependent. The information normally resides in
 * a file, but it could be generated on the fly. This component of
 * the URL is called the <i>path</i> component.
 * <p>
 * A URL can optionally specify a "port", which is the
 * port number to which the TCP connection is made on the remote host
 * machine. If the port is not specified, the default port for
 * the protocol is used instead. For example, the default port for
 * <code>http</code> is <code>80</code>. An alternative port could be
 * specified as:
 * <blockquote><pre>
 *     http://archive.ncsa.uiuc.edu:80/SDG/Software/Mosaic/Demo/url-primer.html
 * </pre></blockquote>
 * <p>
 * The syntax of <code>URL</code> is defined by  <a
 * href="http://www.ietf.org/rfc/rfc2396.txt""><i>RFC&nbsp;2396: Uniform
 * Resource Identifiers (URI): Generic Syntax</i></a>, amended by <a
 * href="http://www.ietf.org/rfc/rfc2732.txt"><i>RFC&nbsp;2732: Format for
 * Literal IPv6 Addresses in URLs</i></a>.
 * <p>
 * A URL may have appended to it a "fragment", also known
 * as a "ref" or a "reference". The fragment is indicated by the sharp
 * sign character "#" followed by more characters. For example,
 * <blockquote><pre>
 *     http://java.sun.com/index.html#chapter1
 * </pre></blockquote>
 * <p>
 * This fragment is not technically part of the URL. Rather, it
 * indicates that after the specified resource is retrieved, the
 * application is specifically interested in that part of the
 * document that has the tag <code>chapter1</code> attached to it. The
 * meaning of a tag is resource specific.
 * <p>
 * An application can also specify a "relative URL",
 * which contains only enough information to reach the resource
 * relative to another URL. Relative URLs are frequently used within
 * HTML pages. For example, if the contents of the URL:
 * <blockquote><pre>
 *     http://java.sun.com/index.html
 * </pre></blockquote>
 * contained within it the relative URL:
 * <blockquote><pre>
 *     FAQ.html
 * </pre></blockquote>
 * it would be a shorthand for:
 * <blockquote><pre>
 *     http://java.sun.com/FAQ.html
 * </pre></blockquote>
 * <p>
 * The relative URL need not specify all the components of a URL. If
 * the protocol, host name, or port number is missing, the value is
 * inherited from the fully specified URL. The file component must be
 * specified. The optional fragment is not inherited.
 *
 * @author  James Gosling
 * @version 1.108, 10/10/06
 * @since JDK1.0 
 */
public final class URL implements java.io.Serializable {

    static final long serialVersionUID = -7627629688361524110L;

    /**
     * The property which specifies the package prefix list to be scanned
     * for protocol handlers.  The value of this property (if any) should
     * be a vertical bar delimited list of package names to search through
     * for a protocol handler to load.  The policy of this class is that
     * all protocol handlers will be in a class called <protocolname>.Handler,
     * and each package in the list is examined in turn for a matching
     * handler.  If none are found (or the property is not specified), the
     * default package prefix, sun.net.www.protocol, is used.  The search
     * proceeds from the first package in the list to the last and stops
     * when a match is found.
     */
    private static final String protocolPathProp = "java.protocol.handler.pkgs";

    /**
     * The protocol to use (ftp, http, nntp, ... etc.) .
     * @serial
     */
    private String protocol;

    /**
     * The host name to connect to.
     * @serial
     */
    private String host;

    /**
     * The protocol port to connect to.
     * @serial
     */
    private int port = -1;

    /**
     * The specified file name on that host. <code>file</code> is
     * defined as <code>path[?query]</code>
     * @serial
     */
    private String file;

    /**
     * The query part of this URL.
     */
    private transient String query;

    /**
     * The authority part of this URL.
     * @serial
     */
    private String authority;

    /**
     * The path part of this URL.
     */
    private transient String path;

    /**
     * The userinfo part of this URL.
     */
    private transient String userInfo;

    /**
     * # reference.
     * @serial
     */
    private String ref;

    /**
     * The host's IP address, used in equals and hashCode.
     * Computed on demand. An uninitialized or unknown hostAddress is null.
     */
    transient InetAddress hostAddress;

    /**
     * The URLStreamHandler for this URL.
     */
    transient URLStreamHandler handler;

    /* Our hash code.
     * @serial
     */
    private int hashCode = -1;

    /**
     * Creates a <code>URL</code> object from the specified
     * <code>protocol</code>, <code>host</code>, <code>port</code>
     * number, and <code>file</code>.<p>
     *
     * <code>host</code> can be expressed as a host name or a literal
     * IP address. If IPv6 literal address is used, it should be
     * enclosed in square brackets (<tt>'['</tt> and <tt>']'</tt>), as
     * specified by <a
     * href="http://www.ietf.org/rfc/rfc2732.txt">RFC&nbsp;2732</a>;
     * However, the literal IPv6 address format defined in <a
     * href="http://www.ietf.org/rfc/rfc2373.txt"><i>RFC&nbsp;2373: IP
     * Version 6 Addressing Architecture</i></a> is also accepted.<p>
     *
     * Specifying a <code>port</code> number of <code>-1</code>
     * indicates that the URL should use the default port for the
     * protocol.<p>
     *
     * If this is the first URL object being created with the specified
     * protocol, a <i>stream protocol handler</i> object, an instance of
     * class <code>URLStreamHandler</code>, is created for that protocol:
     * <ol>
     * <li>If the application has previously set up an instance of
     *     <code>URLStreamHandlerFactory</code> as the stream handler factory,
     *     then the <code>createURLStreamHandler</code> method of that instance
     *     is called with the protocol string as an argument to create the
     *     stream protocol handler.
     * <li>If no <code>URLStreamHandlerFactory</code> has yet been set up,
     *     or if the factory's <code>createURLStreamHandler</code> method
     *     returns <code>null</code>, then the constructor finds the
     *     value of the system property:
     *     <blockquote><pre>
     *         java.protocol.handler.pkgs
     *     </pre></blockquote>
     *     If the value of that system property is not <code>null</code>,
     *     it is interpreted as a list of packages separated by a vertical
     *     slash character '<code>|</code>'. The constructor tries to load
     *     the class named:
     *     <blockquote><pre>
     *         &lt;<i>package</i>&gt;.&lt;<i>protocol</i>&gt;.Handler
     *     </pre></blockquote>
     *     where &lt;<i>package</i>&gt; is replaced by the name of the package
     *     and &lt;<i>protocol</i>&gt; is replaced by the name of the protocol.
     *     If this class does not exist, or if the class exists but it is not
     *     a subclass of <code>URLStreamHandler</code>, then the next package
     *     in the list is tried.
     * <li>If the previous step fails to find a protocol handler, then the
     *     constructor tries to load from a system default package.
     *     <blockquote><pre>
     *         &lt;<i>system default package</i>&gt;.&lt;<i>protocol</i>&gt;.Handler
     *     </pre></blockquote>
     *     If this class does not exist, or if the class exists but it is not a
     *     subclass of <code>URLStreamHandler</code>, then a
     *     <code>MalformedURLException</code> is thrown.
     * </ol>
     *
     * <p>No validation of the inputs is performed by this constructor.
     *
     * @param      protocol   the name of the protocol to use.
     * @param      host       the name of the host.
     * @param      port       the port number on the host.
     * @param      file       the file on the host
     * @exception  MalformedURLException  if an unknown protocol is specified.
     * @see        java.lang.System#getProperty(java.lang.String)
     * @see        java.net.URL#setURLStreamHandlerFactory(
     *			java.net.URLStreamHandlerFactory)
     * @see        java.net.URLStreamHandler
     * @see        java.net.URLStreamHandlerFactory#createURLStreamHandler(
     *                  java.lang.String)
     */
    public URL(String protocol, String host, int port, String file)
	throws MalformedURLException
    {
	this(protocol, host, port, file, null);
    }

    /**
     * Creates a URL from the specified <code>protocol</code>
     * name, <code>host</code> name, and <code>file</code> name. The
     * default port for the specified protocol is used.
     * <p>
     * This method is equivalent to calling the four-argument
     * constructor with the arguments being <code>protocol</code>,
     * <code>host</code>, <code>-1</code>, and <code>file</code>.
     *
     * No validation of the inputs is performed by this constructor.
     *
     * @param      protocol   the name of the protocol to use.
     * @param      host       the name of the host.
     * @param      file       the file on the host.
     * @exception  MalformedURLException  if an unknown protocol is specified.
     * @see        java.net.URL#URL(java.lang.String, java.lang.String,
     *			int, java.lang.String)
     */
    public URL(String protocol, String host, String file)
	    throws MalformedURLException {
	this(protocol, host, -1, file);
    }

    /**
     * Creates a <code>URL</code> object from the specified
     * <code>protocol</code>, <code>host</code>, <code>port</code>
     * number, <code>file</code>, and <code>handler</code>. Specifying
     * a <code>port</code> number of <code>-1</code> indicates that
     * the URL should use the default port for the protocol. Specifying
     * a <code>handler</code> of <code>null</code> indicates that the URL
     * should use a default stream handler for the protocol, as outlined
     * for:
     *     java.net.URL#URL(java.lang.String, java.lang.String, int,
     *                      java.lang.String)
     *
     * <p>If the handler is not null and there is a security manager,
     * the security manager's <code>checkPermission</code>
     * method is called with a
     * <code>NetPermission("specifyStreamHandler")</code> permission.
     * This may result in a SecurityException.
     *
     * No validation of the inputs is performed by this constructor.
     *
     * @param      protocol   the name of the protocol to use.
     * @param      host       the name of the host.
     * @param      port       the port number on the host.
     * @param      file       the file on the host
     * @param	   handler    the stream handler for the URL.
     * @exception  MalformedURLException  if an unknown protocol is specified.
     * @exception  SecurityException
     *        if a security manager exists and its
     *        <code>checkPermission</code> method doesn't allow
     *        specifying a stream handler explicitly.
     * @see        java.lang.System#getProperty(java.lang.String)
     * @see        java.net.URL#setURLStreamHandlerFactory(
     *			java.net.URLStreamHandlerFactory)
     * @see        java.net.URLStreamHandler
     * @see        java.net.URLStreamHandlerFactory#createURLStreamHandler(
     *			java.lang.String)
     * @see        SecurityManager#checkPermission
     * @see        java.net.NetPermission
     */
    public URL(String protocol, String host, int port, String file,
	       URLStreamHandler handler) throws MalformedURLException {
	if (handler != null) {
            SecurityManager sm = System.getSecurityManager();
            if (sm != null) {
                // check for permission to specify a handler
                checkSpecifyHandler(sm);
            }
        }

	protocol = protocol.toLowerCase();
        this.protocol = protocol;
 	if (host != null) {

            /**
	     * if host is a literal IPv6 address,
             * we will make it conform to RFC 2732
	     */
            if (host != null && host.indexOf(':') >= 0
                    && !host.startsWith("[")) {
                host = "["+host+"]";
            }
            this.host = host;

	    if (port < -1) {
		throw new MalformedURLException("Invalid port number :" +
                                                    port);
	    }
            this.port = port;
	    authority = (port == -1) ? host : host + ":" + port;
	}

	Parts parts = new Parts(file);
        path = parts.getPath();
        query = parts.getQuery();

        if (query != null) {
            this.file = path + "?" + query;
        } else {
            this.file = path;
        }
	ref = parts.getRef();	

	// Note: we don't do validation of the URL here. Too risky to change
        // right now, but worth considering for future reference. -br
        if (handler == null &&
            (handler = getURLStreamHandler(protocol)) == null) {
            throw new MalformedURLException("unknown protocol: " + protocol);
        }
        this.handler = handler;
    }

    /**
     * Creates a <code>URL</code> object from the <code>String</code>
     * representation.
     * <p>
     * This constructor is equivalent to a call to the two-argument
     * constructor with a <code>null</code> first argument.
     *
     * @param      spec   the <code>String</code> to parse as a URL.
     * @exception  MalformedURLException  If the string specifies an
     *               unknown protocol.
     * @see        java.net.URL#URL(java.net.URL, java.lang.String)
     */
    public URL(String spec) throws MalformedURLException {
	this(null, spec);
    }