urlstreamhandler.java

kaffe是一个java虚拟机的源代码。里面包含了一些java例程和标准的java包。

/*
 * Java core library component.
 *
 * Copyright (c) 1997, 1998
 *      Transvirtual Technologies, Inc.  All rights reserved.
 *
 * See the file "license.terms" for information on usage and redistribution
 * of this file.
 */

package java.net;

import java.io.IOException;
import java.util.StringTokenizer;

abstract public class URLStreamHandler {

public URLStreamHandler() {
}

abstract protected URLConnection openConnection(URL u) throws IOException;

protected boolean equals(URL url1, URL url2) {
	return sameFile(url1, url2)
	    && (url1.getRef() == null ?
		(url2.getRef() == null)
		: url1.getRef().equals(url2.getRef()));
}

protected int getDefaultPort() {
	return -1;
}

protected InetAddress getHostAddress(URL u) {
	final String host = u.getHost();

	/* spec says to return null if host is not set.
	 * If we called InetAddress.getByName with null,
	 * we would get the localhost. So we need to
	 * explicitely handle hostname == null here.
	 */
	if (host == null) {
		return null;
	}

	try {
		return InetAddress.getByName(host);
	}
	catch (UnknownHostException e) {
		return null;
	}
}

//
// This algorithm works for most common Internet URLS, eg. http, ftp, etc.
// This is how we parse "spec" (between start and limit):
//
//	spec   ->   [//<hostname>[:<port>]][<file>]
//
// Where "port" is restricted to being between 0 and 65535.
//
protected void parseURL(URL u, String spec0, int start, int limit) {
	String spec = spec0.substring(start, limit);
	boolean gotHost = false;

	String host = u.getHost();
	int port = u.getPort();
	String file = u.getFile();
	int posn = 0;

	// Is a host specified?
	if (spec.length() > 2 && spec.startsWith("//")) {
		posn = 2;
		gotHost = true;
		int colon = spec.indexOf(':', posn);
		int slash = spec.indexOf('/', posn);

		// Is a port specified?
		if (colon != -1 && (slash == -1 || colon < slash)) {
			host = spec.substring(posn, colon);
			String portString = spec.substring(colon + 1,
			    slash != -1 ? slash : spec.length());
			try {
				port = Integer.parseInt(portString);
				// JDK1.2 doesn't range check the port nr.
			} catch (NumberFormatException e) {
				port = u.getPort();	
			}
		} else {
			if (slash != -1) {
				host = spec.substring(posn, slash);
			} else {
				host = spec.substring(posn);
			}
		}
		posn = slash;
	} else {
		if (spec.length() == 0) {
			posn = -1;
		}
	}

	// Is a file specified?
	if (posn != -1) {
		if (file.equals("") || spec.charAt(posn) == '/') {
			file = spec.substring(posn);
		} else {
			int lastSlash = file.lastIndexOf('/');
			if (lastSlash == -1) {
				file = spec.substring(posn);
			} else {
				file = file.substring(0, lastSlash + 1)
				    + spec.substring(posn);
			}
		}
	} else {
		if (gotHost) {
			file = "/";
		}
	}

	setURL(u, u.getProtocol(), host, port, compressFile(file), u.getRef());
}

protected boolean sameFile(URL url1, URL url2) {
	if (url1.getProtocol().equals(url2.getProtocol())
	    && url1.getHost().equals(url2.getHost())
	    && (url1.getPort() == url2.getPort()
		|| (url1.getPort() == -1 && url2.getPort() == getDefaultPort())
		|| (url1.getPort() == getDefaultPort() && url2.getPort() == -1))
	    && url1.getFile().equals(url2.getFile())) {
		return (true);
	}
	return (false);
}

protected void setURL(URL u, String protocol, String host, int port,
		String file, String ref) {
	u.set(protocol, host, port, file, ref);
}

protected String toExternalForm(URL u) {
	StringBuffer buf = new StringBuffer();
	buf.append(u.getProtocol());
	buf.append(":");
	String host = u.getHost();
	if (host != null && !u.getHost().equals("")) {
		buf.append("//");
		buf.append(u.getHost());
		if (u.getPort() != -1) {
			buf.append(":");
			buf.append(Integer.toString(u.getPort()));
		}
	}
	buf.append(u.getFile());
	if (u.getRef() != null && !u.getRef().equals("")) {
		buf.append('#');
		buf.append(u.getRef());
	}
	return (buf.toString());
}

private String compressFile(String file) {
	boolean isAbsolute = file.length() > 0 && file.charAt(0) == '/';
	StringTokenizer tok = new StringTokenizer(file, "/");
	int len = tok.countTokens();
	String[] array = new String[len+2];
	int j = 0;
	for (int i = 0; i < len; i++) {
		String str = tok.nextToken();
		if (str.equals("..")) {
			j--;
		}
		else if (!str.equals(".")) {
			if (i+1 < len || file.endsWith("/")) {
				str = str + '/';
			}
			array[j] = str;
			j++;
		}
	}

	// Build a string of the remaining elements.
	StringBuffer buf = new StringBuffer();
	if (isAbsolute) {
		buf.append('/');
	}
	for (int i = 0; i < j; i++) {
		buf.append(array[i]);
	}

	return (buf.toString());
}

}