Java tutorial
/** * * (C) Copyright 2008-2011 syslog4j.org * * All rights reserved. This program and the accompanying materials * are made available under the terms of the GNU Lesser General Public License * (LGPL) version 2.1 which accompanies this distribution, and is available at * http://www.gnu.org/licenses/lgpl-2.1.html * * This library 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 * Lesser General Public License for more details. */ package com.nesscomputing.syslog4j; import java.util.Iterator; import java.util.Map; import java.util.Set; import org.apache.commons.lang3.StringUtils; import com.google.common.base.Preconditions; import com.google.common.collect.Maps; import com.nesscomputing.syslog4j.impl.net.tcp.TCPNetSyslogConfig; import com.nesscomputing.syslog4j.impl.net.udp.UDPNetSyslogConfig; import com.nesscomputing.syslog4j.impl.unix.UnixSyslogConfig; import com.nesscomputing.syslog4j.impl.unix.socket.UnixSocketSyslogConfig; import com.nesscomputing.syslog4j.util.OSDetectUtility; import com.nesscomputing.syslog4j.util.SyslogUtility; /** * This class provides a Singleton interface for Syslog4j client implementations. * * <p>Usage examples:</p> * * <b>Direct</b> * <pre> * Syslog.getInstance("udp").info("log message"); * </pre> * * <b>Via Instance</b> * <pre> * SyslogIF syslog = Syslog.getInstance("udp"); * syslog.info(); * </pre> * * <p>Syslog4j is licensed under the Lesser GNU Public License v2.1. A copy * of the LGPL license is available in the META-INF folder in all * distributions of Syslog4j and in the base directory of the "doc" ZIP.</p> * * @author <syslog4j@productivity.org> * @version $Id: Syslog.java,v 1.23 2011/01/23 20:49:12 cvs Exp $ */ public final class Syslog { protected static final Map<String, SyslogIF> instances = Maps.newHashMap(); /** * Set up the default TCP and UDP Syslog protocols, as * well as UNIX_SYSLOG and UNIX_SOCKET (if running on a Unix-based system). */ static { initialize(); } /** * Syslog is a singleton. */ private Syslog() { // } /** * Use getInstance(protocol) as the starting point for Syslog4j. * * @param protocol - the Syslog protocol to use, e.g. "udp", "tcp", "unix_syslog", "unix_socket", or a custom protocol * @return Returns an instance of SyslogIF. * @throws SyslogRuntimeException */ public static SyslogIF getInstance(String protocol) throws SyslogRuntimeException { String _protocol = protocol.toLowerCase(); if (instances.containsKey(_protocol)) { return instances.get(_protocol); } else { StringBuffer message = new StringBuffer("Syslog protocol \"" + protocol + "\" not defined; call Syslogger.createSyslogInstance(protocol,config) first"); if (instances.size() > 0) { message.append(" or use one of the following instances: "); Iterator<String> i = instances.keySet().iterator(); while (i.hasNext()) { String k = (String) i.next(); message.append(k); if (i.hasNext()) { message.append(' '); } } } throw new SyslogRuntimeException(message.toString()); } } /** * Use createInstance(protocol,config) to create your own Syslog instance. * * <p>First, create an implementation of SyslogConfigIF, such as UdpNetSyslogConfig.</p> * * <p>Second, configure that configuration instance.</p> * * <p>Third, call createInstance(protocol,config) using a short & simple * String for the protocol argument.</p> * * <p>Fourth, either use the returned instance of SyslogIF, or in later code * call getInstance(protocol) with the protocol chosen in the previous step.</p> * * @param protocol * @param config * @return Returns an instance of SyslogIF. * @throws SyslogRuntimeException */ public static SyslogIF createInstance(String protocol, SyslogConfigIF config) throws SyslogRuntimeException { Preconditions.checkArgument(!StringUtils.isBlank(protocol), "Instance protocol cannot be null or empty"); Preconditions.checkArgument(config != null, "SyslogConfig cannot be null"); String syslogProtocol = protocol.toLowerCase(); SyslogIF syslog = null; synchronized (instances) { Preconditions.checkState(!instances.containsKey(syslogProtocol), "Syslog protocol \"%s\" already defined", protocol); try { Class<? extends SyslogIF> syslogClass = config.getSyslogClass(); syslog = syslogClass.newInstance(); } catch (ClassCastException cse) { if (!config.isThrowExceptionOnInitialize()) { throw new SyslogRuntimeException(cse); } else { return null; } } catch (IllegalAccessException iae) { if (!config.isThrowExceptionOnInitialize()) { throw new SyslogRuntimeException(iae); } else { return null; } } catch (InstantiationException ie) { if (!config.isThrowExceptionOnInitialize()) { throw new SyslogRuntimeException(ie); } else { return null; } } syslog.initialize(syslogProtocol, config); instances.put(syslogProtocol, syslog); } return syslog; } /** * @param protocol - Syslog protocol * @return Returns whether the protocol has been previously defined. */ public static boolean exists(String protocol) { if (StringUtils.isBlank(protocol)) { return false; } return instances.containsKey(protocol.toLowerCase()); } /** * shutdown() gracefully shuts down all defined Syslog protocols, * which includes flushing all queues and connections and finally * clearing all instances (including those initialized by default). */ public synchronized static void shutdown() { Set<String> protocols = instances.keySet(); if (protocols.size() > 0) { Iterator<String> i = protocols.iterator(); SyslogUtility.sleep(SyslogConstants.THREAD_LOOP_INTERVAL_DEFAULT); while (i.hasNext()) { String protocol = i.next(); SyslogIF syslog = instances.get(protocol); syslog.shutdown(); } instances.clear(); } } private synchronized static void initialize() { createInstance(SyslogConstants.UDP, new UDPNetSyslogConfig()); createInstance(SyslogConstants.TCP, new TCPNetSyslogConfig()); if (OSDetectUtility.isUnix() && SyslogUtility.isClassExists(SyslogConstants.JNA_NATIVE_CLASS)) { createInstance(SyslogConstants.UNIX_SYSLOG, new UnixSyslogConfig()); createInstance(SyslogConstants.UNIX_SOCKET, new UnixSocketSyslogConfig()); } } static void reset() throws InterruptedException { shutdown(); Thread.sleep(200L); initialize(); } /** * destroyInstance() gracefully shuts down the specified Syslog protocol and * removes the instance from Syslog4j. * * @param protocol - the Syslog protocol to destroy * @throws SyslogRuntimeException */ public synchronized static void destroyInstance(String protocol) throws SyslogRuntimeException { if (StringUtils.isBlank(protocol)) { return; } String _protocol = protocol.toLowerCase(); if (instances.containsKey(_protocol)) { SyslogUtility.sleep(SyslogConstants.THREAD_LOOP_INTERVAL_DEFAULT); SyslogIF syslog = instances.get(_protocol); try { syslog.shutdown(); } finally { instances.remove(_protocol); } } else { throw new SyslogRuntimeException("Cannot destroy protocol \"%s\" instance; call shutdown instead", protocol); } } /** * destroyInstance() gracefully shuts down the specified Syslog instance and * removes it from Syslog4j. * * @param syslog - the Syslog instance to destroy * @throws SyslogRuntimeException */ public synchronized static void destroyInstance(SyslogIF syslog) throws SyslogRuntimeException { if (syslog == null) { return; } String protocol = syslog.getProtocol().toLowerCase(); if (instances.containsKey(protocol)) { try { syslog.shutdown(); } finally { instances.remove(protocol); } } else { throw new SyslogRuntimeException("Cannot destroy protocol \"%s\" instance; call shutdown instead", protocol); } } public static void main(String[] args) throws Exception { SyslogMain.main(args); } }