ProxySelector

AI-generated Key Takeaways

• ProxySelector is an abstract class used for selecting proxy servers when connecting to network resources, allowing for direct or proxied connections based on the URL.

• It provides methods to select proxies (select), handle connection failures (connectFailed), get (getDefault), and set (setDefault) the system-wide proxy selector.

• Subclasses implement the select and connectFailed methods to provide custom proxy selection logic and failure handling.

• URLConnection classes use the select method to determine the appropriate connection approach for each URL request.

• The default ProxySelector enforces system properties related to proxy settings.

public abstract class ProxySelector extends Object

Selects the proxy server to use, if any, when connecting to the network resource referenced by a URL. A proxy selector is a concrete sub-class of this class and is registered by invoking the setDefault method. The currently registered proxy selector can be retrieved by calling getDefault method.

When a proxy selector is registered, for instance, a subclass of URLConnection class should call the select method for each URL request so that the proxy selector can decide if a direct, or proxied connection should be used. The select method returns an iterator over a collection with the preferred connection approach.

If a connection cannot be established to a proxy (PROXY or SOCKS) servers then the caller should call the proxy selector's connectFailed method to notify the proxy selector that the proxy server is unavailable.

The default proxy selector does enforce a set of System Properties related to proxy settings.

Public Constructor Summary

ProxySelector()

Public Method Summary

abstract void	connectFailed(URI uri, SocketAddress sa, IOException ioe) Called to indicate that a connection could not be established to a proxy/socks server.
static ProxySelector	getDefault() Gets the system-wide proxy selector.
abstract List<Proxy>	select(URI uri) Selects all the applicable proxies based on the protocol to access the resource with and a destination address to access the resource at.
static void	setDefault(ProxySelector ps) Sets (or unsets) the system-wide proxy selector.

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 ProxySelector ()

Public Methods

public abstract void connectFailed (URI uri, SocketAddress sa, IOException ioe)

Called to indicate that a connection could not be established to a proxy/socks server. An implementation of this method can temporarily remove the proxies or reorder the sequence of proxies returned by select(URI), using the address and the IOException caught when trying to connect.

Parameters

uri	The URI that the proxy at sa failed to serve.
sa	The socket address of the proxy/SOCKS server
ioe	The I/O exception thrown when the connect failed.

Throws

IllegalArgumentException	if either argument is null

public static ProxySelector getDefault ()

Gets the system-wide proxy selector.

Returns

• the system-wide ProxySelector

Throws

SecurityException	If a security manager has been installed and it denies NetPermission("getProxySelector")

See Also

• setDefault(ProxySelector)

public abstract List<Proxy> select (URI uri)

Selects all the applicable proxies based on the protocol to access the resource with and a destination address to access the resource at. The format of the URI is defined as follow:

• http URI for http connections
• https URI for https connections
• socket://host:port
  for tcp client sockets connections

Parameters

uri	The URI that a connection is required to

Returns

• a List of Proxies. Each element in the the List is of type Proxy; when no proxy is available, the list will contain one element of type Proxy that represents a direct connection.

Throws

IllegalArgumentException	if the argument is null

public static void setDefault (ProxySelector ps)

Sets (or unsets) the system-wide proxy selector. Note: non-standard protocol handlers may ignore this setting.

Parameters

ps	The HTTP proxy selector, or null to unset the proxy selector.

Throws

SecurityException	If a security manager has been installed and it denies NetPermission("setProxySelector")

See Also

• getDefault()