Writing timed tasks in a Java Web project

Prior to the company has a special task scheduling framework, need to use a jar package to add a configuration and annotations can be used, there is a dedicated platform to maintain the running of the machine and monitor the status of execution and so on.

Now suddenly without the tool, but also write a timed task, what to do?

For non-Web applications, we can use quartz, which is simple and powerful.

For Java Web Applications, of course, you can also use Quartz (one blog describes the method: http://blog.csdn.net/sadfishsc/article/details/50808027), but there are more convenient tools, That's what spring comes with to support the Scheduled Tasks feature.

Spring's scheduled tasks in Spring-context, the simple configuration template is as follows:

<?xml version= "1.0" encoding= "UTF-8"? ><beans xmlns= "Http://www.springframework.org/schema/beans" xmlns: Xsi= "Http://www.w3.org/2001/XMLSchema-instance"       xmlns:task= "Http://www.springframework.org/schema/task"       xsi:schemalocation= "Http://www.springframework.org/schema/beans http://www.springframework.org/schema/ Beans/spring-beans-3.2.xsd       Http://www.springframework.org/schema/task Http://www.springframework.org/schema /task/spring-task.xsd ">    <task:scheduler id=" Scheduler "pool-size="/> <task    : Scheduled-tasks>        <!--your task--        <task:scheduled ref= "Xxxtask" method= "execute" cron= "0 0 * * *?" />    </task:scheduled-tasks>    <task:annotation-driven scheduler= "Scheduler"/></beans>

Where Task:scheduler specifies the scheduler to perform a timed task, using Org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler by default;

Task:annotation-driven allows the use of @async and @scheduled annotations;

A task is defined in Task:scheduler-tasks, where the execution cycle can use a cron expression, and you can specify how the delay or frequency is.

There is a conversion cron online tool very useful, recommend to everyone (note here may show 7 characters, remove the last * can be):

http://cron.qqe2.com/

Then there is a problem, usually our online environment is a clustered environment, there are more than one machine, and these scheduled tasks are usually only on a platform, how to control it?

Now think of two ways to share to everyone:

1. Using the Redis global cache

This is not a detailed introduction, you can refer to the following two articles:

http://blog.csdn.net/lihao21/article/details/49104695

http://blog.csdn.net/liubenlong007/article/details/53782934

2. By judging the way the file

By judging whether a file exists, to decide whether to perform the task (whether to load the spring configuration file for the task), refer to the code:

@Componentpublic class Xxxlistener implements Applicationcontextaware {    //Prevent loading multiple    private static final Atomicinteger Init_lock = new Atomicinteger (0);    @Override public    void Setapplicationcontext (ApplicationContext applicationcontext) throws Beansexception {        if (Init_lock.incrementandget () > 1) {            //class has loaded            return;        }        Resource Resource = Applicationcontext.getresource ("classpath:< identification File >");        if (!resource.exists ()) {            //file does not exist, do not start            return;        }                Classpathxmlapplicationcontext context = new Classpathxmlapplicationcontext (applicationcontext);        Context.setconfiglocations ("Classpath:spring/job.xml");        Context.refresh ();    }}

Writing timed tasks in a Java Web project