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URL.javaAPI DocJava SE 6 API45498Tue Jun 10 00:25:42 BST 2008java.net

URL

public final class URL extends Object implements Serializable
Class URL 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:
http://www.socs.uts.edu.au/MosaicDocs-old/url-primer.html

In general, a URL can be broken into several parts. The previous example of a URL indicates that the protocol to use is http (HyperText Transfer Protocol) and that the information resides on a host machine named www.socs.uts.edu.au. The information on that host machine is named /MosaicDocs-old/url-primer.html. 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 path component.

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 http is 80. An alternative port could be specified as:

http://www.socs.uts.edu.au:80/MosaicDocs-old/url-primer.html

The syntax of URL is defined by RFC 2396: Uniform Resource Identifiers (URI): Generic Syntax, amended by RFC 2732: Format for Literal IPv6 Addresses in URLs. The Literal IPv6 address format also supports scope_ids. The syntax and usage of scope_ids is described here.

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,

http://java.sun.com/index.html#chapter1

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 chapter1 attached to it. The meaning of a tag is resource specific.

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:

http://java.sun.com/index.html
contained within it the relative URL:
FAQ.html
it would be a shorthand for:
http://java.sun.com/FAQ.html

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.

The URL class does not itself encode or decode any URL components according to the escaping mechanism defined in RFC2396. It is the responsibility of the caller to encode any fields, which need to be escaped prior to calling URL, and also to decode any escaped fields, that are returned from URL. Furthermore, because URL has no knowledge of URL escaping, it does not recognise equivalence between the encoded or decoded form of the same URL. For example, the two URLs:

 http://foo.com/hello world/ and http://foo.com/hello%20world
would be considered not equal to each other.

Note, the {@link java.net.URI} class does perform escaping of its component fields in certain circumstances. The recommended way to manage the encoding and decoding of URLs is to use {@link java.net.URI}, and to convert between these two classes using {@link #toURI()} and {@link URI#toURL()}.

The {@link URLEncoder} and {@link URLDecoder} classes can also be used, but only for HTML form encoding, which is not the same as the encoding scheme defined in RFC2396.

author
James Gosling
version
1.134, 04/14/06
since
JDK1.0

Fields Summary
static final long
serialVersionUID
private static final String
protocolPathProp
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 .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 String
protocol
The protocol to use (ftp, http, nntp, ... etc.) .
private String
host
The host name to connect to.
private int
port
The protocol port to connect to.
private String
file
The specified file name on that host. file is defined as path[?query]
private transient String
query
The query part of this URL.
private String
authority
The authority part of this URL.
private transient String
path
The path part of this URL.
private transient String
userInfo
The userinfo part of this URL.
private String
ref
# reference.
transient InetAddress
hostAddress
The host's IP address, used in equals and hashCode. Computed on demand. An uninitialized or unknown hostAddress is null.
transient URLStreamHandler
handler
The URLStreamHandler for this URL.
private int
hashCode
static URLStreamHandlerFactory
factory
The URLStreamHandler factory.
static Hashtable
handlers
A table of protocol handlers.
private static Object
streamHandlerLock
Constructors Summary
public URL(String protocol, String host, int port, String file)
Creates a URL object from the specified protocol, host, port number, and file.

host 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 ('[' and ']'), as specified by RFC 2732; However, the literal IPv6 address format defined in RFC 2373: IP Version 6 Addressing Architecture is also accepted.

Specifying a port number of -1 indicates that the URL should use the default port for the protocol.

If this is the first URL object being created with the specified protocol, a stream protocol handler object, an instance of class URLStreamHandler, is created for that protocol:

  1. If the application has previously set up an instance of URLStreamHandlerFactory as the stream handler factory, then the createURLStreamHandler method of that instance is called with the protocol string as an argument to create the stream protocol handler.
  2. If no URLStreamHandlerFactory has yet been set up, or if the factory's createURLStreamHandler method returns null, then the constructor finds the value of the system property:
    java.protocol.handler.pkgs
    
    If the value of that system property is not null, it is interpreted as a list of packages separated by a vertical slash character '|'. The constructor tries to load the class named:
    <package>.<protocol>.Handler
    
    where <package> is replaced by the name of the package and <protocol> 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 URLStreamHandler, then the next package in the list is tried.
  3. If the previous step fails to find a protocol handler, then the constructor tries to load from a system default package.
    <system default package>.<protocol>.Handler
    
    If this class does not exist, or if the class exists but it is not a subclass of URLStreamHandler, then a MalformedURLException is thrown.

Protocol handlers for the following protocols are guaranteed to exist on the search path :-

http, https, ftp, file, and jar
Protocol handlers for additional protocols may also be available.

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)


                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               			                                         
            
	 
    
	this(protocol, host, port, file, null);
    
public URL(String protocol, String host, String file)
Creates a URL from the specified protocol name, host name, and file name. The default port for the specified protocol is used.

This method is equivalent to calling the four-argument constructor with the arguments being protocol, host, -1, and file. 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)

	this(protocol, host, -1, file);
    
public URL(String protocol, String host, int port, String file, URLStreamHandler handler)
Creates a URL object from the specified protocol, host, port number, file, and handler. Specifying a port number of -1 indicates that the URL should use the default port for the protocol. Specifying a handler of null 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)

If the handler is not null and there is a security manager, the security manager's checkPermission method is called with a NetPermission("specifyStreamHandler") 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 checkPermission 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

	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;
    
public URL(String spec)
Creates a URL object from the String representation.

This constructor is equivalent to a call to the two-argument constructor with a null first argument.

param
spec the String 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)

	this(null, spec);
    
public URL(URL context, String spec)
Creates a URL by parsing the given spec within a specified context. The new URL is created from the given context URL and the spec argument as described in RFC2396 "Uniform Resource Identifiers : Generic * Syntax" :
<scheme>://<authority><path>?<query>#<fragment>
The reference is parsed into the scheme, authority, path, query and fragment parts. If the path component is empty and the scheme, authority, and query components are undefined, then the new URL is a reference to the current document. Otherwise, the fragment and query parts present in the spec are used in the new URL.

If the scheme component is defined in the given spec and does not match the scheme of the context, then the new URL is created as an absolute URL based on the spec alone. Otherwise the scheme component is inherited from the context URL.

If the authority component is present in the spec then the spec is treated as absolute and the spec authority and path will replace the context authority and path. If the authority component is absent in the spec then the authority of the new URL will be inherited from the context.

If the spec's path component begins with a slash character "/" then the path is treated as absolute and the spec path replaces the context path.

Otherwise, the path is treated as a relative path and is appended to the context path, as described in RFC2396. Also, in this case, the path is canonicalized through the removal of directory changes made by occurences of ".." and ".".

For a more detailed description of URL parsing, refer to RFC2396.

param
context the context in which to parse the specification.
param
spec the String to parse as a URL.
exception
MalformedURLException if no protocol is specified, or an unknown protocol is found.
see
java.net.URL#URL(java.lang.String, java.lang.String, int, java.lang.String)
see
java.net.URLStreamHandler
see
java.net.URLStreamHandler#parseURL(java.net.URL, java.lang.String, int, int)

	this(context, spec, null);
    
public URL(URL context, String spec, URLStreamHandler handler)
Creates a URL by parsing the given spec with the specified handler within a specified context. If the handler is null, the parsing occurs as with the two argument constructor.

param
context the context in which to parse the specification.
param
spec the String to parse as a URL.
param
handler the stream handler for the URL.
exception
MalformedURLException if no protocol is specified, or an unknown protocol is found.
exception
SecurityException if a security manager exists and its checkPermission method doesn't allow specifying a stream handler.
see
java.net.URL#URL(java.lang.String, java.lang.String, int, java.lang.String)
see
java.net.URLStreamHandler
see
java.net.URLStreamHandler#parseURL(java.net.URL, java.lang.String, int, int)

	String original = spec;
	int i, limit, c;
	int start = 0;
	String newProtocol = null;
	boolean aRef=false;
	boolean isRelative = false;

	// Check for permission to specify a handler
	if (handler != null) {
	    SecurityManager sm = System.getSecurityManager();
	    if (sm != null) {
		checkSpecifyHandler(sm);
	    }
	}

	try {
	    limit = spec.length();
	    while ((limit > 0) && (spec.charAt(limit - 1) <= ' ")) {
		limit--;	//eliminate trailing whitespace
	    }
	    while ((start < limit) && (spec.charAt(start) <= ' ")) {
		start++;	// eliminate leading whitespace
	    }

	    if (spec.regionMatches(true, start, "url:", 0, 4)) {
		start += 4;
	    }
	    if (start < spec.length() && spec.charAt(start) == '#") {
		/* we're assuming this is a ref relative to the context URL.
		 * This means protocols cannot start w/ '#', but we must parse
		 * ref URL's like: "hello:there" w/ a ':' in them.
		 */
		aRef=true;
	    }
	    for (i = start ; !aRef && (i < limit) &&
		     ((c = spec.charAt(i)) != '/") ; i++) {
		if (c == ':") {

		    String s = spec.substring(start, i).toLowerCase();
		    if (isValidProtocol(s)) {
			newProtocol = s;
			start = i + 1;
		    }
		    break;
		}
	    }

	    // Only use our context if the protocols match.
	    protocol = newProtocol;
	    if ((context != null) && ((newProtocol == null) ||
			    newProtocol.equalsIgnoreCase(context.protocol))) {
                // inherit the protocol handler from the context
		// if not specified to the constructor
		if (handler == null) {
		    handler = context.handler;
		}

                // If the context is a hierarchical URL scheme and the spec
		// contains a matching scheme then maintain backwards
		// compatibility and treat it as if the spec didn't contain
		// the scheme; see 5.2.3 of RFC2396
		if (context.path != null && context.path.startsWith("/"))
		    newProtocol = null;

                if (newProtocol == null) {
                    protocol = context.protocol;
		    authority = context.authority;
		    userInfo = context.userInfo;
                    host = context.host;
                    port = context.port;
                    file = context.file;
		    path = context.path;
		    isRelative = true;
                }
	    }

	    if (protocol == null) {
		throw new MalformedURLException("no protocol: "+original);
	    }

	    // Get the protocol handler if not specified or the protocol
	    // of the context could not be used
	    if (handler == null &&
	        (handler = getURLStreamHandler(protocol)) == null) {
		throw new MalformedURLException("unknown protocol: "+protocol);
	    }

	    this.handler = handler;

	    i = spec.indexOf('#", start);
	    if (i >= 0) {
		ref = spec.substring(i + 1, limit);
		limit = i;
	    }
	    
	    /*
	     * Handle special case inheritance of query and fragment
	     * implied by RFC2396 section 5.2.2.
	     */
	    if (isRelative && start == limit) {
		query = context.query;
		if (ref == null) {
		    ref = context.ref;
		}
	    }

	    handler.parseURL(this, spec, start, limit);

	} catch(MalformedURLException e) {
	    throw e;
	} catch(Exception e) {
	    throw new MalformedURLException(e.getMessage());
	}
    
Methods Summary
private voidcheckSpecifyHandler(java.lang.SecurityManager sm)

	sm.checkPermission(SecurityConstants.SPECIFY_HANDLER_PERMISSION);
    
public booleanequals(java.lang.Object obj)
Compares this URL for equality with another object.

If the given object is not a URL then this method immediately returns false.

Two URL objects are equal if they have the same protocol, reference equivalent hosts, have the same port number on the host, and the same file and fragment of the file.

Two hosts are considered equivalent if both host names can be resolved into the same IP addresses; else if either host name can't be resolved, the host names must be equal without regard to case; or both host names equal to null.

Since hosts comparison requires name resolution, this operation is a blocking operation.

Note: The defined behavior for equals is known to be inconsistent with virtual hosting in HTTP.

param
obj the URL to compare against.
return
true if the objects are the same; false otherwise.

        if (!(obj instanceof URL))
            return false;
	URL u2 = (URL)obj;

        return handler.equals(this, u2);
    
public java.lang.StringgetAuthority()
Gets the authority part of this URL.

return
the authority part of this URL
since
1.3

	return authority;
    
public final java.lang.ObjectgetContent()
Gets the contents of this URL. This method is a shorthand for:
openConnection().getContent()

return
the contents of this URL.
exception
IOException if an I/O exception occurs.
see
java.net.URLConnection#getContent()

	return openConnection().getContent();
    
public final java.lang.ObjectgetContent(java.lang.Class[] classes)
Gets the contents of this URL. This method is a shorthand for:
openConnection().getContent(Class[])

param
classes an array of Java types
return
the content object of this URL that is the first match of the types specified in the classes array. null if none of the requested types are supported.
exception
IOException if an I/O exception occurs.
see
java.net.URLConnection#getContent(Class[])
since
1.3

	return openConnection().getContent(classes);
    
public intgetDefaultPort()
Gets the default port number of the protocol associated with this URL. If the URL scheme or the URLStreamHandler for the URL do not define a default port number, then -1 is returned.

return
the port number
since
1.4

	return handler.getDefaultPort();
    
public java.lang.StringgetFile()
Gets the file name of this URL. The returned file portion will be the same as getPath(), plus the concatenation of the value of getQuery(), if any. If there is no query portion, this method and getPath() will return identical results.

return
the file name of this URL, or an empty string if one does not exist

	return file;
    
public java.lang.StringgetHost()
Gets the host name of this URL, if applicable. The format of the host conforms to RFC 2732, i.e. for a literal IPv6 address, this method will return the IPv6 address enclosed in square brackets ('[' and ']').

return
the host name of this URL.

	return host;
    
public java.lang.StringgetPath()
Gets the path part of this URL.

return
the path part of this URL, or an empty string if one does not exist
since
1.3

	return path;
    
public intgetPort()
Gets the port number of this URL.

return
the port number, or -1 if the port is not set

	return port;
    
public java.lang.StringgetProtocol()
Gets the protocol name of this URL.

return
the protocol of this URL.

	return protocol;
    
public java.lang.StringgetQuery()
Gets the query part of this URL.

return
the query part of this URL, or null if one does not exist
since
1.3

	return query;
    
public java.lang.StringgetRef()
Gets the anchor (also known as the "reference") of this URL.

return
the anchor (also known as the "reference") of this URL, or null if one does not exist

	return ref;
    
static java.net.URLStreamHandlergetURLStreamHandler(java.lang.String protocol)
Returns the Stream Handler.

param
protocol the protocol to use


                   
        

	URLStreamHandler handler = (URLStreamHandler)handlers.get(protocol);
	if (handler == null) {

	    boolean checkedWithFactory = false;

	    // Use the factory (if any)
	    if (factory != null) {
		handler = factory.createURLStreamHandler(protocol);
		checkedWithFactory = true;
	    }

	    // Try java protocol handler
	    if (handler == null) {
		String packagePrefixList = null;

		packagePrefixList
		    = (String) java.security.AccessController.doPrivileged(
                    new sun.security.action.GetPropertyAction(
		        protocolPathProp,""));
		if (packagePrefixList != "") {
		    packagePrefixList += "|";
		}

		// REMIND: decide whether to allow the "null" class prefix
		// or not.
		packagePrefixList += "sun.net.www.protocol";

		StringTokenizer packagePrefixIter =
		    new StringTokenizer(packagePrefixList, "|");

		while (handler == null &&
		       packagePrefixIter.hasMoreTokens()) {

		    String packagePrefix =
		      packagePrefixIter.nextToken().trim();
		    try {
		        String clsName = packagePrefix + "." + protocol +
			  ".Handler";
			Class cls = null;
			try {
                            cls = Class.forName(clsName);
                        } catch (ClassNotFoundException e) {
			    ClassLoader cl = ClassLoader.getSystemClassLoader();
			    if (cl != null) {
			        cls = cl.loadClass(clsName);
			    }
			}
			if (cls != null) {
			    handler  =
			      (URLStreamHandler)cls.newInstance();
			}
		    } catch (Exception e) {
			// any number of exceptions can get thrown here
		    }
		}
	    }

	    synchronized (streamHandlerLock) {

		URLStreamHandler handler2 = null;

		// Check again with hashtable just in case another
		// thread created a handler since we last checked
		handler2 = (URLStreamHandler)handlers.get(protocol);

		if (handler2 != null) {
		    return handler2;
		}

		// Check with factory if another thread set a
		// factory since our last check
		if (!checkedWithFactory && factory != null) {
		    handler2 = factory.createURLStreamHandler(protocol);
		}

		if (handler2 != null) {
		    // The handler from the factory must be given more
		    // importance. Discard the default handler that
		    // this thread created.
		    handler = handler2;
		}

		// Insert this handler into the hashtable
		if (handler != null) {
		    handlers.put(protocol, handler);
		}

	    }
	}

	return handler;

    
public java.lang.StringgetUserInfo()
Gets the userInfo part of this URL.

return
the userInfo part of this URL, or null if one does not exist
since
1.3

	return userInfo;
    
public synchronized inthashCode()
Creates an integer suitable for hash table indexing.

The hash code is based upon all the URL components relevant for URL comparison. As such, this operation is a blocking operation.

return
a hash code for this URL.

	if (hashCode != -1)
            return hashCode;

        hashCode = handler.hashCode(this);
	return hashCode;
    
private booleanisValidProtocol(java.lang.String protocol)

	int len = protocol.length();
        if (len < 1)
            return false;
        char c = protocol.charAt(0);
        if (!Character.isLetter(c))
            return false;
	for (int i = 1; i < len; i++) {
	    c = protocol.charAt(i);
	    if (!Character.isLetterOrDigit(c) && c != '." && c != '+" &&
		c != '-") {
		return false;
	    }
	}
	return true;
    
public java.net.URLConnectionopenConnection()
Returns a URLConnection object that represents a connection to the remote object referred to by the URL.

A new connection is opened every time by calling the openConnection method of the protocol handler for this URL.

If for the URL's protocol (such as HTTP or JAR), there exists a public, specialized URLConnection subclass belonging to one of the following packages or one of their subpackages: java.lang, java.io, java.util, java.net, the connection returned will be of that subclass. For example, for HTTP an HttpURLConnection will be returned, and for JAR a JarURLConnection will be returned.

return
a URLConnection to the URL.
exception
IOException if an I/O exception occurs.
see
java.net.URL#URL(java.lang.String, java.lang.String, int, java.lang.String)
see
java.net.URLConnection
see
java.net.URLStreamHandler#openConnection(java.net.URL)

	return handler.openConnection(this);
    
public java.net.URLConnectionopenConnection(java.net.Proxy proxy)
Same as openConnection(), except that the connection will be made through the specified proxy; Protocol handlers that do not support proxing will ignore the proxy parameter and make a normal connection. Calling this method preempts the system's default ProxySelector settings.

param
proxy the Proxy through which this connection will be made. If direct connection is desired, Proxy.NO_PROXY should be specified.
return
a URLConnection to the URL.
exception
IOException if an I/O exception occurs.
exception
SecurityException if a security manager is present and the caller doesn't have permission to connect to the proxy.
exception
IllegalArgumentException will be thrown if proxy is null, or proxy has the wrong type
exception
UnsupportedOperationException if the subclass that implements the protocol handler doesn't support this method.
see
java.net.URL#URL(java.lang.String, java.lang.String, int, java.lang.String)
see
java.net.URLConnection
see
java.net.URLStreamHandler#openConnection(java.net.URL, java.net.Proxy)
since
1.5

	if (proxy == null) {
	    throw new IllegalArgumentException("proxy can not be null");
	}
	
	SecurityManager sm = System.getSecurityManager();
	if (proxy.type() != Proxy.Type.DIRECT && sm != null) {
	    InetSocketAddress epoint = (InetSocketAddress) proxy.address();
	    if (epoint.isUnresolved())
		sm.checkConnect(epoint.getHostName(), epoint.getPort());
	    else
		sm.checkConnect(epoint.getAddress().getHostAddress(),
				epoint.getPort());
	}
	return handler.openConnection(this, proxy);
    
public final java.io.InputStreamopenStream()
Opens a connection to this URL and returns an InputStream for reading from that connection. This method is a shorthand for:
openConnection().getInputStream()

return
an input stream for reading from the URL connection.
exception
IOException if an I/O exception occurs.
see
java.net.URL#openConnection()
see
java.net.URLConnection#getInputStream()

	return openConnection().getInputStream();
    
private synchronized voidreadObject(java.io.ObjectInputStream s)
readObject is called to restore the state of the URL from the stream. It reads the components of the URL and finds the local stream handler.

	s.defaultReadObject();	// read the fields
	if ((handler = getURLStreamHandler(protocol)) == null) {
	    throw new IOException("unknown protocol: " + protocol);
	}

        // Construct authority part
        if (authority == null &&
	    ((host != null && host.length() > 0) || port != -1)) {
	    if (host == null)
		host = "";
            authority = (port == -1) ? host : host + ":" + port;

            // Handle hosts with userInfo in them
            int at = host.lastIndexOf('@");
            if (at != -1) {
                userInfo = host.substring(0, at);
                host = host.substring(at+1);
	    }
        } else if (authority != null) {
            // Construct user info part
            int ind = authority.indexOf('@");
            if (ind != -1)
                userInfo = authority.substring(0, ind);
	}

        // Construct path and query part
        path = null;
        query = null;
        if (file != null) {
	    // Fix: only do this if hierarchical?
            int q = file.lastIndexOf('?");
            if (q != -1) {
                query = file.substring(q+1);
                path = file.substring(0, q);
            } else
                path = file;
        }
    
public booleansameFile(java.net.URL other)
Compares two URLs, excluding the fragment component.

Returns true if this URL and the other argument are equal without taking the fragment component into consideration.

param
other the URL to compare against.
return
true if they reference the same remote object; false otherwise.

        return handler.sameFile(this, other);
    
protected voidset(java.lang.String protocol, java.lang.String host, int port, java.lang.String authority, java.lang.String userInfo, java.lang.String path, java.lang.String query, java.lang.String ref)
Sets the specified 8 fields of the URL. This is not a public method so that only URLStreamHandlers can modify URL fields. URLs are otherwise constant.

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
authority the authority part for the url
param
userInfo the username and password
param
path the file on the host
param
ref the internal reference in the URL
param
query the query part of this URL
since
1.3

	synchronized (this) {
	    this.protocol = protocol;
	    this.host = host;
	    this.port = port;
	    this.file = query == null ? path : path + "?" + query;
            this.userInfo = userInfo;
            this.path = path;
	    this.ref = ref;
	    /* This is very important. We must recompute this after the
	     * URL has been changed. */
	    hashCode = -1;
            hostAddress = null;
            this.query = query;
            this.authority = authority;
	}
    
protected voidset(java.lang.String protocol, java.lang.String host, int port, java.lang.String file, java.lang.String ref)
Sets the fields of the URL. This is not a public method so that only URLStreamHandlers can modify URL fields. URLs are otherwise constant.

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
ref the internal reference in the URL

	synchronized (this) {
	    this.protocol = protocol;
	    this.host = host;
            authority = port == -1 ? host : host + ":" + port;
	    this.port = port;
	    this.file = file;
	    this.ref = ref;
	    /* This is very important. We must recompute this after the
	     * URL has been changed. */
	    hashCode = -1;
            hostAddress = null;
            int q = file.lastIndexOf('?");
            if (q != -1) {
                query = file.substring(q+1);
                path = file.substring(0, q);
            } else
                path = file;
	}
    
public static voidsetURLStreamHandlerFactory(java.net.URLStreamHandlerFactory fac)
Sets an application's URLStreamHandlerFactory. This method can be called at most once in a given Java Virtual Machine.

The URLStreamHandlerFactory instance is used to construct a stream protocol handler from a protocol name.

If there is a security manager, this method first calls the security manager's checkSetFactory method to ensure the operation is allowed. This could result in a SecurityException.

param
fac the desired factory.
exception
Error if the application has already set a factory.
exception
SecurityException if a security manager exists and its checkSetFactory method doesn't allow the operation.
see
java.net.URL#URL(java.lang.String, java.lang.String, int, java.lang.String)
see
java.net.URLStreamHandlerFactory
see
SecurityManager#checkSetFactory

	synchronized (streamHandlerLock) {
	    if (factory != null) {
		throw new Error("factory already defined");
	    }
	    SecurityManager security = System.getSecurityManager();
	    if (security != null) {
		security.checkSetFactory();
	    }
	    handlers.clear();
	    factory = fac;
	}
    
public java.lang.StringtoExternalForm()
Constructs a string representation of this URL. The string is created by calling the toExternalForm method of the stream protocol handler for this object.

return
a string representation of this object.
see
java.net.URL#URL(java.lang.String, java.lang.String, int, java.lang.String)
see
java.net.URLStreamHandler#toExternalForm(java.net.URL)

	return handler.toExternalForm(this);
    
public java.lang.StringtoString()
Constructs a string representation of this URL. The string is created by calling the toExternalForm method of the stream protocol handler for this object.

return
a string representation of this object.
see
java.net.URL#URL(java.lang.String, java.lang.String, int, java.lang.String)
see
java.net.URLStreamHandler#toExternalForm(java.net.URL)

	return toExternalForm();
    
public java.net.URItoURI()
Returns a {@link java.net.URI} equivalent to this URL. This method functions in the same way as new URI (this.toString()).

Note, any URL instance that complies with RFC 2396 can be converted to a URI. However, some URLs that are not strictly in compliance can not be converted to a URI.

exception
URISyntaxException if this URL is not formatted strictly according to to RFC2396 and cannot be converted to a URI.
return
a URI instance equivalent to this URL.
since
1.5

	return new URI (toString());
    
private synchronized voidwriteObject(java.io.ObjectOutputStream s)
WriteObject is called to save the state of the URL to an ObjectOutputStream. The handler is not saved since it is specific to this system.

serialData
the default write object value. When read back in, the reader must ensure that calling getURLStreamHandler with the protocol variable returns a valid URLStreamHandler and throw an IOException if it does not.

	s.defaultWriteObject();	// write the fields