URLStreamHandler

AI-generated Key Takeaways

• URLStreamHandler is an abstract class serving as the base for all stream protocol handlers.

• It defines how to establish connections for protocols like HTTP or HTTPS, handling protocol-specific logic.

• Subclasses are loaded automatically when a new protocol is encountered during URL creation, ensuring efficient resource management.

• It offers protected methods for tasks such as parsing URLs, retrieving host addresses, opening connections, and comparing URLs, promoting code reusability and maintainability.

• The openConnection method establishes connections to the resource specified by a URL and returns a URLConnection object for interaction.

public abstract class URLStreamHandler extends Object

The abstract class URLStreamHandler is the common superclass for all stream protocol handlers. A stream protocol handler knows how to make a connection for a particular protocol type, such as http or https.

In most cases, an instance of a URLStreamHandler subclass is not created directly by an application. Rather, the first time a protocol name is encountered when constructing a URL, the appropriate stream protocol handler is automatically loaded.

See Also

• URL.URL(java.lang.String, java.lang.String, int, java.lang.String)

Public Constructor Summary

URLStreamHandler()

Protected Method Summary

boolean	equals(URL u1, URL u2) Provides the default equals calculation.
int	getDefaultPort() Returns the default port for a URL parsed by this handler.
synchronized InetAddress	getHostAddress(URL u) Get the IP address of our host.
int	hashCode(URL u) Provides the default hash calculation.
boolean	hostsEqual(URL u1, URL u2) Compares the host components of two URLs.
abstract URLConnection	openConnection(URL u) Opens a connection to the object referenced by the URL argument.
URLConnection	openConnection(URL u, Proxy p) Same as openConnection(URL), except that the connection will be made through the specified proxy; Protocol handlers that do not support proxying will ignore the proxy parameter and make a normal connection.
void	parseURL(URL u, String spec, int start, int limit) Parses the string representation of a URL into a URL object.
boolean	sameFile(URL u1, URL u2) Compare two urls to see whether they refer to the same file, i.e., having the same protocol, host, port, and path.
void	setURL(URL u, String protocol, String host, int port, String file, String ref) This method is deprecated. Use setURL(URL, String, String, int, String, String, String, String);
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.
String	toExternalForm(URL u) Converts a URL of a specific protocol to a String.

Inherited Method Summary

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

Public Constructors

public URLStreamHandler ()

Protected Methods

protected boolean equals (URL u1, URL u2)

Provides the default equals calculation. May be overidden by handlers for other protocols that have different requirements for equals(). This method requires that none of its arguments is null. This is guaranteed by the fact that it is only called by java.net.URL class.

Parameters

u1	a URL object
u2	a URL object

Returns

• true if the two urls are considered equal, ie. they refer to the same fragment in the same file.

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 for a URL parsed by this handler.

protected synchronized InetAddress getHostAddress (URL u)

Get the IP address of our host. An empty host field or a DNS failure will result in a null return.

Parameters

u	a URL object

Returns

• an InetAddress representing the host IP address.

protected int hashCode (URL u)

Provides the default hash calculation. May be overidden by handlers for other protocols that have different requirements for hashCode calculation.

Parameters

u	a URL object

Returns

• an int suitable for hash table indexing

protected boolean hostsEqual (URL u1, URL u2)

Compares the host components of two URLs.

Parameters

u1	the URL of the first host to compare
u2	the URL of the second host to compare

Returns

• true if and only if they are equal, false otherwise.

protected abstract URLConnection openConnection (URL u)

Opens a connection to the object referenced by the URL argument. This method should be overridden by a subclass.

If for the handler'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.

Parameters

u	the URL that this connects to.

Returns

• a URLConnection object for the URL.

Throws

IOException	if an I/O error occurs while opening the connection.

protected URLConnection openConnection (URL u, Proxy p)

Same as openConnection(URL), except that the connection will be made through the specified proxy; Protocol handlers that do not support proxying will ignore the proxy parameter and make a normal connection. Calling this method preempts the system's default ProxySelector settings.

Parameters

u	the URL that this connects to.
p	the proxy through which the connection will be made. If direct connection is desired, Proxy.NO_PROXY should be specified.

Returns

• a URLConnection object for the URL.

Throws

IOException	if an I/O error occurs while opening the connection.
IllegalArgumentException	if either u or p is null, or p has the wrong type.
UnsupportedOperationException	if the subclass that implements the protocol doesn't support this method.

protected void parseURL (URL u, String spec, int start, int limit)

Parses the string representation of a URL into a URL object.

If there is any inherited context, then it has already been copied into the URL argument.

The parseURL method of URLStreamHandler parses the string representation as if it were an http specification. Most URL protocol families have a similar parsing. A stream protocol handler for a protocol that has a different syntax must override this routine.

Parameters

u	the URL to receive the result of parsing the spec.
spec	the String representing the URL that must be parsed.
start	the character index at which to begin parsing. This is just past the ':' (if there is one) that specifies the determination of the protocol name.
limit	the character position to stop parsing at. This is the end of the string or the position of the "#" character, if present. All information after the sharp sign indicates an anchor.

protected boolean sameFile (URL u1, URL u2)

Compare two urls to see whether they refer to the same file, i.e., having the same protocol, host, port, and path. This method requires that none of its arguments is null. This is guaranteed by the fact that it is only called indirectly by java.net.URL class.

Parameters

u1	a URL object
u2	a URL object

Returns

• true if u1 and u2 refer to the same file

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

This method is deprecated.
Use setURL(URL, String, String, int, String, String, String, String);

Sets the fields of the URL argument to the indicated values. Only classes derived from URLStreamHandler are able to use this method to set the values of the URL fields.

Parameters

u	the URL to modify.
protocol	the protocol name. This value is ignored since 1.2.
host	the remote host value for the URL.
port	the port on the remote machine.
file	the file.
ref	the reference.

Throws

SecurityException	if the protocol handler of the URL is different from this one

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. Only classes derived from URLStreamHandler are able to use this method to set the values of the URL fields.

Parameters

u	the URL to modify.
protocol	the protocol name.
host	the remote host value for the URL.
port	the port on the remote machine.
authority	the authority part for the URL.
userInfo	the userInfo part of the URL.
path	the path component of the URL.
query	the query part for the URL.
ref	the reference.

Throws

SecurityException	if the protocol handler of the URL is different from this one

See Also

• URL.set(java.lang.String, java.lang.String, int, java.lang.String, java.lang.String)

protected String toExternalForm (URL u)

Converts a URL of a specific protocol to a String.

Parameters

u	the URL.

Returns

• a string representation of the URL argument.