Java tutorial
/* * RHQ Management Platform * Copyright (C) 2005-2008 Red Hat, Inc. * All rights reserved. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License, version 2, as * published by the Free Software Foundation, and/or the GNU Lesser * General Public License, version 2.1, also as published by the Free * Software Foundation. * * This program 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 and the GNU Lesser General Public License * for more details. * * You should have received a copy of the GNU General Public License * and the GNU Lesser General Public License along with this program; * if not, write to the Free Software Foundation, Inc., * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ package org.rhq.plugins.platform.content.yum; import java.io.File; import java.io.PrintWriter; import java.net.InetAddress; import java.net.ServerSocket; import java.net.Socket; import java.net.SocketTimeoutException; import java.net.UnknownHostException; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; /** * Provides a bare-bones http server for yum requests. It is designed to be a non-concurrent server to ensure that * requests are handled <i>one at a tiem</i>. This is neccessary because the server caches the local metadata files. A * concurrent server would either duplicate the work required (separate files per thread) to construct the <i>local</i> * metadata or each thread would step-on the shared metadata files. Either way, a concurrent server should be sufficient * for a single client. * * @author jortel */ public class YumServer { /** * The server socket used to listen for requests. */ private ServerSocket socket = null; /** * The server thread. */ private Thread thread = null; /** * The server thread run flag. */ private boolean run = true; /** * The server's context. */ YumContext context; /** * The yum configuration file constant */ private static final String yumconf = "/etc/yum.repos.d/rhq.repo"; private final Log log = LogFactory.getLog(YumServer.class); /** * Starts the server. This will initialize and start a server thread. If the server is already running, this request * is treated as a restart. The server thread is stopped (run=false) and a new thread is initialized are started. * * @param context The server's context. * * @throws Exception On all errors. */ public void start(YumContext context) throws Exception { this.context = context; if (thread != null) { log.warn("Already started, restarting ..."); halt(); } setupYumConfiguration(); int port = context.baseurl().getPort(); InetAddress host = bindAddress(); log.info("Binding: " + host + ":" + port); socket = new ServerSocket(port, 20, host); socket.setSoTimeout(2000); start(port); } /** * Stop (halt/run=false) the server thread. The request is ignored if the server thread isn't running. */ public void halt() { if (thread == null) { log.info("Stop ignored: not running"); return; } try { run = false; thread.join(); thread = null; socket.close(); log.info("Stopped"); } catch (Exception e) { log.error("halt falied", e); } finally { removeYumConfiguration(); } } public boolean isStarted() { return this.thread != null; } /** * Clean the cached metadata. */ public void cleanMetadata() { try { Request request = new Request(this, null); request.cleanMetadata(); } catch (Exception e) { log.error("Clean metadata failed", e); } } /** * Start a server thread listening on the <i>loopback</i> ethernet interface on the specifed port. The thread * listens for yum/http requests uisng a finite timeout so changes in the <i>run</i> flag can be detected. * * @param port The tcp port to listen on. */ private void start(int port) { run = true; thread = new Thread("yum:" + port) { @Override public void run() { log.info("listening ..."); while (run) { listen(); } } }; thread.start(); log.info("Started, listening on port: " + port); } /** * Listen for and process requests. */ private void listen() { try { Socket client = socket.accept(); client.setTcpNoDelay(true); client.setSoLinger(false, 0); Request request = new Request(this, client); request.process(); } catch (SocketTimeoutException te) { // expected } catch (Exception e) { log.warn("listen failed", e); run = false; } } /** * Setup the /etc/yum.repos.d configuration for this server. The file is over-written to ensure proper content. */ private void setupYumConfiguration() { File file = new File(yumconf); try { PrintWriter writer = new PrintWriter(file); try { writer.println("[rhq]"); writer.println("name=RHQ"); writer.printf("baseurl=%s\n", context.baseurl()); writer.printf("metadata_expire=%d\n", context.getMetadataCacheTimeout()); writer.println("enabled=1"); writer.println("gpgcheck=0"); writer.println("keepalive=0"); writer.println("timeout=90"); } finally { writer.close(); } } catch (Exception e) { String msg = "The yum repo configuration file '" + file + "' could not be created/updated!"; log.error(msg, e); } } /** * Remove the etc/yum.repos.d/ackbar.conf configuration file. */ public void removeYumConfiguration() { File file = new File(yumconf); try { file.delete(); } catch (Exception e) { String msg = "The yum repo configuration file '" + file + "' could not be removed!"; log.error(msg, e); } } /** * Get the bind IP address. * * @return An address to bind. * * @throws UnknownHostException */ private InetAddress bindAddress() throws UnknownHostException { byte[] host = { 127, 0, 0, 1 }; return InetAddress.getByAddress(host); } }