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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code 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
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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*/
package java.net;
import java.io.IOException;
import java.util.List;
import sun.security.util.SecurityConstants;
/**
* 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
* {@link java.net.ProxySelector#setDefault setDefault} method. The
* currently registered proxy selector can be retrieved by calling
* {@link java.net.ProxySelector#getDefault getDefault} method.
*
* <p> When a proxy selector is registered, for instance, a subclass
* of URLConnection class should call the {@link #select select}
* method for each URL request so that the proxy selector can decide
* if a direct, or proxied connection should be used. The {@link
* #select select} method returns an iterator over a collection with
* the preferred connection approach.
*
* <p> If a connection cannot be established to a proxy (PROXY or
* SOCKS) servers then the caller should call the proxy selector's
* {@link #connectFailed connectFailed} method to notify the proxy
* selector that the proxy server is unavailable. </p>
*
* <P>The default proxy selector does enforce a
* <a href="doc-files/net-properties.html#Proxies">set of System Properties</a>
* related to proxy settings.</P>
*
* @author Yingxian Wang
* @author Jean-Christophe Collet
* @since 1.5
*/
public abstract class ProxySelector {
/**
* The system wide proxy selector that selects the proxy server to
* use, if any, when connecting to a remote object referenced by
* an URL.
*
* @see #setDefault(ProxySelector)
*/
private static ProxySelector theProxySelector;
static {
try {
Class<?> c = Class.forName("sun.net.spi.DefaultProxySelector");
if (c != null && ProxySelector.class.isAssignableFrom(c)) {
theProxySelector = (ProxySelector) c.newInstance();
}
} catch (Exception e) {
theProxySelector = null;
}
}
/**
* Gets the system-wide proxy selector.
*
* @throws SecurityException
* If a security manager has been installed and it denies
* {@link NetPermission}{@code ("getProxySelector")}
* @see #setDefault(ProxySelector)
* @return the system-wide {@code ProxySelector}
* @since 1.5
*/
public static ProxySelector getDefault() {
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
sm.checkPermission(SecurityConstants.GET_PROXYSELECTOR_PERMISSION);
}
return theProxySelector;
}
/**
* Sets (or unsets) the system-wide proxy selector.
*
* Note: non-standard protocol handlers may ignore this setting.
*
* @param ps The HTTP proxy selector, or
* {@code null} to unset the proxy selector.
*
* @throws SecurityException
* If a security manager has been installed and it denies
* {@link NetPermission}{@code ("setProxySelector")}
*
* @see #getDefault()
* @since 1.5
*/
public static void setDefault(ProxySelector ps) {
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
sm.checkPermission(SecurityConstants.SET_PROXYSELECTOR_PERMISSION);
}
theProxySelector = ps;
}
/**
* 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:
* <UL>
* <LI>http URI for http connections</LI>
* <LI>https URI for https connections
* <LI>{@code socket://host:port}<br>
* for tcp client sockets connections</LI>
* </UL>
*
* @param uri
* The URI that a connection is required to
*
* @return a List of Proxies. Each element in the
* the List is of type
* {@link java.net.Proxy Proxy};
* when no proxy is available, the list will
* contain one element of type
* {@link java.net.Proxy Proxy}
* that represents a direct connection.
* @throws IllegalArgumentException if the argument is null
*/
public abstract List<Proxy> select(URI uri);
/**
* 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 {@link #select(URI)}, using the address
* and the IOException caught when trying to connect.
*
* @param uri
* The URI that the proxy at sa failed to serve.
* @param sa
* The socket address of the proxy/SOCKS server
*
* @param ioe
* The I/O exception thrown when the connect failed.
* @throws IllegalArgumentException if either argument is null
*/
public abstract void connectFailed(URI uri, SocketAddress sa, IOException ioe);
}