A ServletContextListner that can be used to initialize Quartz.
配置和集成 Quartz 到 Web 应用的一种方式。从 2.3 版本的 Servlet API 开始，能创建监听器，由容器在其生命周期中的某个特定时间回调。其中的一个监听器接口叫做 java.servlet.ServletContextListener，它包括有两个方法：
public void contextInitialized(ServletContextEvent sce); public void contextDestroyed(ServeltContextEvent sce);
容器会在启动和关闭的时候相应的调用这两个方法。这就可以在 contextInitialized() 方法中初始化 Quartz Scheduler，并通过 contextDestroyed() 方法关闭它。
下面是QuartzInitializerListener 源码：
/**//*
* Copyright 2004-2005 OpenSymphony
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy
* of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
*/
/**//*
* Previously Copyright (c) 2001-2004 James House
*/
package org.quartz.ee.servlet;
import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import org.quartz.Scheduler;
import org.quartz.impl.StdSchedulerFactory;
/** *//**
* <p>
* A ServletContextListner that can be used to initialize Quartz.
* </p>
*
* <p>
* You'll want to add something like this to your WEB-INF/web.xml file:
*
* <pre>
* <context-param>
* <param-name>config-file</param-name>
* <param-value>/some/path/my_quartz.properties</param-value>
* </context-param>
* <context-param>
* <param-name>shutdown-on-unload</param-name>
* <param-value>true</param-value>
* </context-param>
* <context-param>
* <param-name>start-scheduler-on-load</param-name>
* <param-value>true</param-value>
* </context-param>
*
* <listener>
* <listener-class>
* org.quartz.ee.servlet.QuartzInitializerListener
* </listener-class>
* </listener>
* </pre>
*
* </p>
* <p>
* The init parameter 'config-file' can be used to specify the path (and
* filename) of your Quartz properties file. If you leave out this parameter,
* the default ("quartz.properties") will be used.
* </p>
*
* <p>
* The init parameter 'shutdown-on-unload' can be used to specify whether you
* want scheduler.shutdown() called when the servlet is unloaded (usually when
* the application server is being shutdown). Possible values are "true" or
* "false". The default is "true".
* </p>
*
* <p>
* The init parameter 'start-scheduler-on-load' can be used to specify whether
* you want the scheduler.start() method called when the servlet is first loaded.
* If set to false, your application will need to call the start() method before
* the scheduler begins to run and process jobs. Possible values are "true" or
* "false". The default is "true", which means the scheduler is started.
* </p>
*
* A StdSchedulerFactory instance is stored into the ServletContext. You can gain access
* to the factory from a ServletContext instance like this:
* <br>
* <pre>
* StdSchedulerFactory factory = (StdSchedulerFactory) ctx
* .getAttribute(QuartzInitializerListener.QUARTZ_FACTORY_KEY);</pre>
* <p>
* The init parameter 'servlet-context-factory-key' can be used to override the
* name under which the StdSchedulerFactory is stored into the ServletContext, in
* which case you will want to use this name rather than
* <code>QuartzInitializerListener.QUARTZ_FACTORY_KEY</code> in the above example.
* </p>
*
* <p>
* The init parameter 'start-delay-seconds' can be used to specify the amount
* of time to wait after initializing the scheduler before scheduler.start()
* is called.
* </p>
*
* Once you have the factory instance, you can retrieve the Scheduler instance by calling
* <code>getScheduler()</code> on the factory.
*
* @author James House
* @author Chuck Cavaness
* @author John Petrocik
*/
public class QuartzInitializerListener implements ServletContextListener {
public static final String QUARTZ_FACTORY_KEY = "org.quartz.impl.StdSchedulerFactory.KEY";
private boolean performShutdown = true;
private Scheduler scheduler = null;
/**//*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* Interface.
*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/
public void contextInitialized(ServletContextEvent sce) {
System.out.println("Quartz Initializer Servlet loaded, initializing Scheduler");
ServletContext servletContext = sce.getServletContext();
StdSchedulerFactory factory;
try {
String configFile = servletContext.getInitParameter("config-file");
String shutdownPref = servletContext.getInitParameter("shutdown-on-unload");
if (shutdownPref != null) {
performShutdown = Boolean.valueOf(shutdownPref).booleanValue();
}
// get Properties
if (configFile != null) {
factory = new StdSchedulerFactory(configFile);
} else {
factory = new StdSchedulerFactory();
}
// Always want to get the scheduler, even if it isn't starting,
// to make sure it is both initialized and registered.
scheduler = factory.getScheduler();
// Should the Scheduler being started now or later
String startOnLoad = servletContext
.getInitParameter("start-scheduler-on-load");
int startDelay = 0;
String startDelayS = servletContext.getInitParameter("start-delay-seconds");
try {
if(startDelayS != null && startDelayS.trim().length() > 0)
startDelay = Integer.parseInt(startDelayS);
} catch(Exception e) {
System.out.println("Cannot parse value of 'start-delay-seconds' to an integer: " + startDelayS + ", defaulting to 5 seconds.");
startDelay = 5;
}
/**//*
* If the "start-scheduler-on-load" init-parameter is not specified,
* the scheduler will be started. This is to maintain backwards
* compatability.
*/
if (startOnLoad == null || (Boolean.valueOf(startOnLoad).booleanValue())) {
if(startDelay <= 0) {
// Start now
scheduler.start();
System.out.println("Scheduler has been started");
}
else {
// Start delayed
scheduler.startDelayed(startDelay);
System.out.println("Scheduler will start in " + startDelay + " seconds.");
}
} else {
System.out.println("Scheduler has not been started. Use scheduler.start()");
}
String factoryKey =
servletContext.getInitParameter("servlet-context-factory-key");
if (factoryKey == null) {
factoryKey = QUARTZ_FACTORY_KEY;
}
System.out.println("Storing the Quartz Scheduler Factory in the servlet context at key: "
+ factoryKey);
servletContext.setAttribute(factoryKey, factory);
} catch (Exception e) {
System.out.println("Quartz Scheduler failed to initialize: " + e.toString());
e.printStackTrace();
}
}
public void contextDestroyed(ServletContextEvent sce) {
if (!performShutdown) {
return;
}
try {
if (scheduler != null) {
scheduler.shutdown();
}
} catch (Exception e) {
System.out.println("Quartz Scheduler failed to shutdown cleanly: " + e.toString());
e.printStackTrace();
}
System.out.println("Quartz Scheduler successful shutdown.");
}
}