Chip 1997 October/Chip_1997-10_cd.bin/tema/sybase/powerj/java.z/URLStreamHandler.java

Text File | 1996-05-03 | 5KB | 156 lines

/*
 * @(#)URLStreamHandler.java    1.14 96/03/06
 *
 * Copyright (c) 1994 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Permission to use, copy, modify, and distribute this software and its
 * documentation for NON-COMMERCIAL purposes and without fee is hereby
 * granted provided that this copyright notice appears in all copies. Please
 * refer to the file "copyright.html" for further important copyright and
 * licensing information.
 *
 * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
 * SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE,
 * OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY
 * LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR
 * ITS DERIVATIVES.
 */

package java.net;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Hashtable;

/**
 * Abstract class for URL stream openers.
 * Subclasses of this class know how to create streams for particular
 * protocol types.
 *
 * @version     1.12, 18 Dec 1995
 * @author     James Gosling
 */
public abstract class URLStreamHandler {
    /**
     * Opens an input stream to the object referenced by the URL.  This method should be
     * overridden by a subclass.
     * @param u the URL that this connects to
     */
    abstract protected URLConnection openConnection(URL u) throws IOException;

    /**
     * This method is called to parse the string spec into URL u.  If
     * there is any inherited context then it has already been copied
     * into u.  The parameters <code>start</code> and
     * <code>limit</code> refer to the range of characters in spec
     * that should be parsed.  The default method uses parsing rules
     * that match the http spec, which most URL protocol families
     * follow.  If you are writing a protocol handler that has a
     * different syntax, override this routine.

     * @param    u the URL to receive the result of parsing the spec
     * @param    spec the URL string to parse
     * @param    start the character position to start parsing at.  This is
     *         just past the ':' (if there is one).
     * @param    limit the character position to stop parsing at.  This is
     *         the end of the string or the position of the "#"
     *         character if present (the "#" reference syntax is
     *         protocol independent).
     */
    protected void parseURL(URL u, String spec, int start, int limit) {
    String protocol = u.getProtocol();
    String host = u.getHost();
    int port = u.getPort();
    String file = u.getFile();
    String ref = u.getRef();

    int i;
    if ((start <= limit - 2) &&
        (spec.charAt(start) == '/') &&
        (spec.charAt(start + 1) == '/')) {
        start += 2;
        i = spec.indexOf('/', start);
        if (i < 0) {
        i = limit;
        }
        int prn = spec.indexOf(':', start);
        port = -1;
        if ((prn < i) && (prn >= 0)) {
        try {
            port = Integer.parseInt(spec.substring(prn + 1, i));
        } catch(Exception e) {
            // ignore bogus port numbers
        }
        if (prn > start) {
            host = spec.substring(start, prn);
        }
        } else {
        host = spec.substring(start, i);
        }
        start = i;
        file = null;
    } else if (host == null) {
        host = "";
    }
    if (start < limit) {
        if (spec.charAt(start) == '/') {
        file = spec.substring(start, limit);
        } else {
        file = (file != null ?
              file.substring(0, file.lastIndexOf('/')) : "")
            + "/" + spec.substring(start, limit);
        }
    }
    if ((file == null) || (file.length() == 0)) {
        file = "/";
    }
    while ((i = file.indexOf("/./")) >= 0) {
        file = file.substring(0, i) + file.substring(i + 2);
    }
    while ((i = file.indexOf("/../")) >= 0) {
        if ((limit = file.lastIndexOf('/', i - 1)) >= 0) {
        file = file.substring(0, limit) + file.substring(i + 3);
        } else {
        file = file.substring(i + 3);
        }
    }

    u.set(protocol, host, port, file, ref);
    }

    /**
     * Reverses the parsing of the URL.  This should probably be overridden if
     * you override parseURL().
     * @param u the URL
     * @return    the textual representation of the fully qualified URL (i.e.
     *        after the context and canonicalization have been applied).
     */
    protected String toExternalForm(URL u) {
    String result = u.getProtocol() + ":";
    if ((u.getHost() != null) && (u.getHost().length() > 0)) {
        result = result + "//" + u.getHost();
        if (u.getPort() != -1) {
        result += ":" + u.getPort();
        }
    }
    result += u.getFile();
    if (u.getRef() != null) {
        result += "#" + u.getRef();
    }
    return result;
    }

    /**
     * Calls the (protected) set method out of the URL given.  Only
     * classes derived from URLStreamHandler are supposed to be able
     * to call the set() method on a URL.
     * @see URL#set
     */
    protected void setURL(URL u, String protocol, String host, int port,
              String file, String ref) {
        u.set(protocol, host, port, file, ref);
    }
}