Java tutorial
/* * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved. * 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. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ 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)) { @SuppressWarnings("deprecation") ProxySelector tmp = (ProxySelector) c.newInstance(); theProxySelector = tmp; } } 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 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); /** * Returns a ProxySelector which uses the given proxy address for all HTTP * and HTTPS requests. If proxy is {@code null} then proxying is disabled. * * @param proxyAddress * The address of the proxy * * @return a ProxySelector * * @since 9 */ public static ProxySelector of(InetSocketAddress proxyAddress) { return new StaticProxySelector(proxyAddress); } static class StaticProxySelector extends ProxySelector { private static final List<Proxy> NO_PROXY_LIST = List.of(Proxy.NO_PROXY); final List<Proxy> list; StaticProxySelector(InetSocketAddress address) { Proxy p; if (address == null) { p = Proxy.NO_PROXY; } else { p = new Proxy(Proxy.Type.HTTP, address); } list = List.of(p); } @Override public void connectFailed(URI uri, SocketAddress sa, IOException e) { /* ignore */ } @Override public synchronized List<Proxy> select(URI uri) { String scheme = uri.getScheme().toLowerCase(); if (scheme.equals("http") || scheme.equals("https")) { return list; } else { return NO_PROXY_LIST; } } } }