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java.net

Class URLStreamHandler

public abstract class URLStreamHandler
extends Object
This class is the superclass of all URL protocol handlers. The URL class loads the appropriate protocol handler to establish a connection to a (possibly) remote service (eg, "http", "ftp") and to do protocol specific parsing of URL's. Refer to the URL class documentation for details on how that class locates and loads protocol handlers.

A protocol handler implementation should override the openConnection() method, and optionally override the parseURL() and toExternalForm() methods if necessary. (The default implementations will parse/write all URL's in the same form as http URL's). A protocol specific subclass of URLConnection will most likely need to be created as well.

Note that the instance methods in this class are called as if they were static methods. That is, a URL object to act on is passed with every call rather than the caller assuming the URL is stored in an instance variable of the "this" object.

The methods in this class are protected and accessible only to subclasses. URLStreamConnection objects are intended for use by the URL class only, not by other classes (unless those classes are implementing protocols).

See Also:
URL

Constructor Summary

URLStreamHandler()
Creates a URLStreamHander

Method Summary

protected boolean
equals(URL url1, URL url2)
This is the default method for computing whether two URLs are equivalent.
protected int
getDefaultPort()
Returns the default port for a URL parsed by this handler.
protected InetAddress
getHostAddress(URL url)
Get the IP address of our host.
protected int
hashCode(URL url)
Provides the default hash calculation.
protected boolean
hostsEqual(URL url1, URL url2)
Compares the host components of two URLs.
protected abstract URLConnection
openConnection(URL url)
Returns a URLConnection for the passed in URL.
protected void
parseURL(URL url, String spec, int start, int end)
This method parses the string passed in as a URL and set's the instance data fields in the URL object passed in to the various values parsed out of the string.
protected boolean
sameFile(URL url1, URL url2)
Compares two URLs, excluding the fragment component
protected void
setURL(URL u, String protocol, String host, int port, String file, String ref)
Deprecated. 1.2 Please use #setURL(URL,String,String,int,String,String,String,String);
protected void
setURL(URL u, String protocol, String host, int port, String authority, String userInfo, String path, String query, String ref)
Sets the fields of the URL argument to the indicated values
protected String
toExternalForm(URL url)
This method converts a URL object into a String.

Methods inherited from class java.lang.Object

clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

URLStreamHandler

public URLStreamHandler()
Creates a URLStreamHander

Method Details

equals

protected boolean equals(URL url1,
                         URL url2)
This is the default method for computing whether two URLs are equivalent. This method assumes that neither URL is null.
Parameters:
url1 - An URL object
url2 - Another URL object
Returns:
True if both given URLs are equal, false otherwise.

getDefaultPort

protected int getDefaultPort()
Returns the default port for a URL parsed by this handler. This method is meant to be overidden by handlers with default port numbers.
Returns:
The default port number.

getHostAddress

protected InetAddress getHostAddress(URL url)
Get the IP address of our host. An empty host field or a DNS failure will result in a null return.
Parameters:
url - The URL to return the host address for.
Returns:
The address of the hostname in url.

hashCode

protected int hashCode(URL url)
Provides the default hash calculation. May be overidden by handlers for other protocols that have different requirements for hashCode calculation.
Parameters:
url - The URL to calc the hashcode for.
Returns:
The hashcode for the given URL.

hostsEqual

protected boolean hostsEqual(URL url1,
                             URL url2)
Compares the host components of two URLs.
Parameters:
url1 - The first URL.
url2 - The second URL.
Returns:
True if both URLs contain the same host.

openConnection

protected abstract URLConnection openConnection(URL url)
            throws IOException
Returns a URLConnection for the passed in URL. Note that this should not actually create the connection to the (possibly) remote host, but rather simply return a URLConnection object. The connect() method of URL connection is used to establish the actual connection, possibly after the caller sets up various connection options.
Parameters:
url - The URL to get a connection object for
Returns:
A URLConnection object for the given URL
Throws:
IOException - If an error occurs

parseURL

protected void parseURL(URL url,
                        String spec,
                        int start,
                        int end)
This method parses the string passed in as a URL and set's the instance data fields in the URL object passed in to the various values parsed out of the string. The start parameter is the position to start scanning the string. This is usually the position after the ":" which terminates the protocol name. The end parameter is the position to stop scanning. This will be either the end of the String, or the position of the "#" character, which separates the "file" portion of the URL from the "anchor" portion.

This method assumes URL's are formatted like http protocol URL's, so subclasses that implement protocols with URL's the follow a different syntax should override this method. The lone exception is that if the protocol name set in the URL is "file", this method will accept an empty hostname (i.e., "file:///"), which is legal for that protocol

Parameters:
url - The URL object in which to store the results
spec - The String-ized URL to parse
start - The position in the string to start scanning from
end - The position in the string to stop scanning

sameFile

protected boolean sameFile(URL url1,
                           URL url2)
Compares two URLs, excluding the fragment component
Parameters:
url1 - The first url
url2 - The second url to compare with the first
Returns:
True if both URLs point to the same file, false otherwise.

setURL

protected void setURL(URL u,
                      String protocol,
                      String host,
                      int port,
                      String file,
                      String ref)

Deprecated. 1.2 Please use #setURL(URL,String,String,int,String,String,String,String);

This methods sets the instance variables representing the various fields of the URL to the values passed in.
Parameters:
u - The URL to modify
protocol - The protocol to set
host - The host name to et
port - The port number to set
file - The filename to set
ref - The reference
Throws:
SecurityException - If the protocol handler of the URL is different from this one

setURL

protected void setURL(URL u,
                      String protocol,
                      String host,
                      int port,
                      String authority,
                      String userInfo,
                      String path,
                      String query,
                      String ref)
Sets the fields of the URL argument to the indicated values
Parameters:
u - The URL to modify
protocol - The protocol to set
host - The host name to set
port - The port number to set
authority - The authority to set
userInfo - The user information to set
path - The path/filename to set
query - The query part to set
ref - The reference
Throws:
SecurityException - If the protocol handler of the URL is different from this one

toExternalForm

protected String toExternalForm(URL url)
This method converts a URL object into a String. This method creates Strings in the mold of http URL's, so protocol handlers which use URL's that have a different syntax should override this method
Parameters:
url - The URL object to convert
Returns:
A string representation of the url
URLStreamHandler.java -- Abstract superclass for all protocol handlers Copyright (C) 1998, 1999, 2002, 2003, 2004 Free Software Foundation, Inc. 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 the Free Software Foundation; either version 2, or (at your option) any later version. GNU Classpath 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 for more details. You should have received a copy of the GNU General Public License along with GNU Classpath; see the file COPYING. If not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. Linking this library statically or dynamically with other modules is making a combined work based on this library. Thus, the terms and conditions of the GNU General Public License cover the whole combination. As a special exception, the copyright holders of this library give you permission to link this library with independent modules to produce an executable, regardless of the license terms of these independent modules, and to copy and distribute the resulting executable under terms of your choice, provided that you also meet, for each linked independent module, the terms and conditions of the license of that module. An independent module is a module which is not derived from or based on this library. If you modify this library, you may extend this exception to your version of the library, but you are not obligated to do so. If you do not wish to do so, delete this exception statement from your version.

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