彻底理解spring的定制任务（scheduling） 作者: wuhua

starxing

信做软件的朋友都有这样的经历，我的软件是不是少了点什么东西呢？比如定时任务啊，
  
就拿新闻发布系统来说，如果新闻的数据更新太快，势必涉及一个问题，这些新闻不能由人工的去发布，应该让系统自己发布，这就需要用到定时定制任务了，以前
定制任务无非就是设计一个Thread，并且设置运行时间片，让它到了那个时间执行一次，就ok了，让系统启动的时候启动它，想来也够简单的。不过有了
spring，我想这事情就更简单了。
看看spring的配置文件，想来就只有这个配置文件了
xml 代码
bean id="infoCenterAutoBuildTask"      class="com.teesoo.teanet.scheduling.InfoCenterAutoBuildTask">      property name="baseService" ref="baseService" />      property name="htmlCreator" ref="htmlCreator" />  bean>    bean id="scheduledTask"      class="org.springframework.scheduling.timer.ScheduledTimerTask">            property name="delay" value="10000" />            property name="period" value="1000000" />      property name="timerTask" ref="infoCenterAutoBuildTask" />  bean>      bean id="timerFactory" class="org.springframework.scheduling.timer.TimerFactoryBean">     property name="scheduledTimerTasks">         list>                          ref bean="scheduledTask" />         list>     property>  bean>  
上面三个配置文件中只有一个配置文件是涉及到您自己的class的，其他的都是spring的类。很简单吧
我们只需要涉及一个class让他继承java.util.TimerTask;
java 代码
BaseTask extends java.util.TimerTask {   //用户只需要实现这个方面，把自己的任务放到这里   public void run(){   }   }  

下面让我们来看看 spring的源代码
java 代码
/*   * Copyright 2002-2005 the original author or authors.   *    * 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.   */    package org.springframework.scheduling.timer;     import java.util.TimerTask;     /**   * JavaBean that describes a scheduled TimerTask, consisting of   * the TimerTask itself (or a Runnable to create a TimerTask for)   * and a delay plus period. Period needs to be specified;   * there is no point in a default for it.   *   *
The JDK Timer does not offer more sophisticated scheduling
  * options such as  cron expressions. Consider using Quartz for   * such advanced needs.   *   *
Note that Timer uses a TimerTask instance that is shared
  * between repeated executions, in contrast to Quartz which   * instantiates a new Job for each execution.   *   * @author Juergen Hoeller   * @since 19.02.2004   * @see java.util.TimerTask   * @see java.util.Timer#schedule(TimerTask, long, long)   * @see java.util.Timer#scheduleAtFixedRate(TimerTask, long, long)   */  public class ScheduledTimerTask {         private TimerTask timerTask;         private long delay = 0;         private long period = 0;         private boolean fixedRate = false;           /**       * Create a new ScheduledTimerTask,       * to be populated via bean properties.       * @see #setTimerTask       * @see #setDelay       * @see #setPeriod       * @see #setFixedRate       */      public ScheduledTimerTask() {       }         /**       * Create a new ScheduledTimerTask, with default       * one-time execution without delay.       * @param timerTask the TimerTask to schedule       */      public ScheduledTimerTask(TimerTask timerTask) {           this.timerTask = timerTask;       }         /**       * Create a new ScheduledTimerTask, with default       * one-time execution with the given delay.       * @param timerTask the TimerTask to schedule       * @param delay the delay before starting the task for the first time (ms)       */      public ScheduledTimerTask(TimerTask timerTask, long delay) {           this.timerTask = timerTask;           this.delay = delay;       }         /**       * Create a new ScheduledTimerTask.       * @param timerTask the TimerTask to schedule       * @param delay the delay before starting the task for the first time (ms)       * @param period the period between repeated task executions (ms)       * @param fixedRate whether to schedule as fixed-rate execution       */      public ScheduledTimerTask(TimerTask timerTask, long delay, long period, boolean fixedRate) {           this.timerTask = timerTask;           this.delay = delay;           this.period = period;           this.fixedRate = fixedRate;       }         /**       * Create a new ScheduledTimerTask, with default       * one-time execution without delay.       * @param timerTask the Runnable to schedule as TimerTask       */      public ScheduledTimerTask(Runnable timerTask) {           setRunnable(timerTask);       }         /**       * Create a new ScheduledTimerTask, with default       * one-time execution with the given delay.       * @param timerTask the Runnable to schedule as TimerTask       * @param delay the delay before starting the task for the first time (ms)       */      public ScheduledTimerTask(Runnable timerTask, long delay) {           setRunnable(timerTask);           this.delay = delay;       }         /**       * Create a new ScheduledTimerTask.       * @param timerTask the Runnable to schedule as TimerTask       * @param delay the delay before starting the task for the first time (ms)       * @param period the period between repeated task executions (ms)       * @param fixedRate whether to schedule as fixed-rate execution       */      public ScheduledTimerTask(Runnable timerTask, long delay, long period, boolean fixedRate) {           setRunnable(timerTask);           this.delay = delay;           this.period = period;           this.fixedRate = fixedRate;       }           /**       * Set the Runnable to schedule as TimerTask.       * @see DelegatingTimerTask       */      public void setRunnable(Runnable timerTask) {           this.timerTask = new DelegatingTimerTask(timerTask);       }         /**       * Set the TimerTask to schedule.       */      public void setTimerTask(TimerTask timerTask) {           this.timerTask = timerTask;       }         /**       * Return the TimerTask to schedule.       */      public TimerTask getTimerTask() {           return timerTask;       }         /**       * Set the delay before starting the task for the first time,       * in milliseconds. Default is 0, immediately starting the       * task after successful scheduling.       */      public void setDelay(long delay) {           this.delay = delay;       }         /**       * Return the delay before starting the job for the first time.       */      public long getDelay() {           return delay;       }         /**       * Set the period between repeated task executions, in milliseconds.       * Default is 0, leading to one-time execution. In case of a positive       * value, the task will be executed repeatedly, with the given interval       * inbetween executions.       *
Note that the semantics of the period vary between fixed-rate
      * and fixed-delay execution.       * @see #setFixedRate       */      public void setPeriod(long period) {           this.period = period;       }         /**       * Return the period between repeated task executions.       */      public long getPeriod() {           return period;       }         /**       * Set whether to schedule as fixed-rate execution, rather than       * fixed-delay execution. Default is "false", i.e. fixed delay.       *
See Timer javadoc for details on those execution modes.
      * @see java.util.Timer#schedule(TimerTask, long, long)       * @see java.util.Timer#scheduleAtFixedRate(TimerTask, long, long)       */      public void setFixedRate(boolean fixedRate) {           this.fixedRate = fixedRate;       }         /**       * Return whether to schedule as fixed-rate execution.       */      public boolean isFixedRate() {           return fixedRate;       }     }                                            
说实话这个类也没什么，只是简单的包装了我们的timertask，里面也就只有几个属性，一个是时间片，一个是任务等。
真正运行我们的任务的类是：
java 代码
/*   * Copyright 2002-2006 the original author or authors.   *   * 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.   */    package org.springframework.scheduling.timer;     import java.util.Timer;     import org.apache.commons.logging.Log;   import org.apache.commons.logging.LogFactory;     import org.springframework.beans.factory.DisposableBean;   import org.springframework.beans.factory.FactoryBean;   import org.springframework.beans.factory.InitializingBean;     /**   * FactoryBean that sets up a JDK 1.3+ Timer and exposes it for bean references.   *   *
Allows for registration of ScheduledTimerTasks, automatically starting
  * the Timer on initialization and cancelling it on destruction of the context.   * In scenarios that just require static registration of tasks at startup,   * there is no need to access the Timer instance itself in application code.   *   *
Note that Timer uses a TimerTask instance that is shared between
  * repeated executions, in contrast to Quartz which instantiates a new   * Job for each execution.   *   * @author Juergen Hoeller   * @since 19.02.2004   * @see ScheduledTimerTask   * @see java.util.Timer   * @see java.util.TimerTask   */  public class TimerFactoryBean implements FactoryBean, InitializingBean, DisposableBean {         protected final Log logger = LogFactory.getLog(getClass());         private ScheduledTimerTask[] scheduledTimerTasks;         private boolean daemon = false;         private Timer timer;           /**       * Register a list of ScheduledTimerTask objects with the Timer that       * this FactoryBean creates. Depending on each SchedulerTimerTask's       * settings, it will be registered via one of Timer's schedule methods.       * @see java.util.Timer#schedule(java.util.TimerTask, long)       * @see java.util.Timer#schedule(java.util.TimerTask, long, long)       * @see java.util.Timer#scheduleAtFixedRate(java.util.TimerTask, long, long)       */      public void setScheduledTimerTasks(ScheduledTimerTask[] scheduledTimerTasks) {           this.scheduledTimerTasks = scheduledTimerTasks;       }         /**       * Set whether the timer should use a daemon thread,       * just executing as long as the application itself is running.       *
Default is "false": The timer will automatically get cancelled on
      * destruction of this FactoryBean. Hence, if the application shuts down,       * tasks will by default finish their execution. Specify "true" for eager       * shutdown of threads that execute tasks.       * @see java.util.Timer#Timer(boolean)       */      public void setDaemon(boolean daemon) {           this.daemon = daemon;       }           public void afterPropertiesSet() {           logger.info("Initializing Timer");           this.timer = createTimer(this.daemon);             // Register all ScheduledTimerTasks.           if (this.scheduledTimerTasks != null) {               for (int i = 0; i this.scheduledTimerTasks.length; i++) {                   ScheduledTimerTask scheduledTask = this.scheduledTimerTasks;                   if (scheduledTask.getPeriod() > 0) {                       // repeated task execution                       if (scheduledTask.isFixedRate()) {                           this.timer.scheduleAtFixedRate(                                   scheduledTask.getTimerTask(), scheduledTask.getDelay(), scheduledTask.getPeriod());                       }                       else {                           this.timer.schedule(                                   scheduledTask.getTimerTask(), scheduledTask.getDelay(), scheduledTask.getPeriod());                       }                   }                   else {                       // One-time task execution.                       this.timer.schedule(scheduledTask.getTimerTask(), scheduledTask.getDelay());                   }               }           }       }         /**       * Create a new Timer instance. Called by afterPropertiesSet.       * Can be overridden in subclasses to provide custom Timer subclasses.       * @param daemon whether to create a Timer that runs as daemon thread       * @return a new Timer instance       * @see #afterPropertiesSet()       * @see java.util.Timer#Timer(boolean)       */      protected Timer createTimer(boolean daemon) {           return new Timer(daemon);       }           public Object getObject() {           return this.timer;       }         public Class getObjectType() {           return Timer.class;       }         public boolean isSingleton() {           return true;       }           /**       * Cancel the Timer on bean factory shutdown, stopping all scheduled tasks.       * @see java.util.Timer#cancel()       */      public void destroy() {           logger.info("Cancelling Timer");           this.timer.cancel();       }     }   
               
               
               

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