How to start in Web Application examples explain the background tasks

Abstract: How to start in Web Application examples explain the background tasks

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We often in Web applications need to write its own services, the purpose of this paper is to provide you with a solution.

Principle

The principle of the programme is to write an interface to achieve the ServletContextListener category, there are two such methods:

Public void contextInitialized (ServletContextEvent sce)

It is activated when the call in the application; Another method is:

Public void contextDestroyed (ServletContextEvent sce)

The method is applied at the end of the call.

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We have to start the application logic on the background contextInitialized method achieved; to release background applications work in the occupied contextDestroyed resources to deal with them. But we started background task is often required, such as time, frequency, and so on, here I use an open-source components: quartz.

Steps

1, writing business called categories:

/ / DumbJob.java import org.quartz .*; import java.util .*; public class DumbJob implements Job (public DumbJob () () public void execute (JobExecutionContext context) throws JobExecutionException (/ / write processing code here. )) </ Td> </ tr> </ table>

This is the main function of quartz in the scheduling of the prescribed rules call implement the necessary business logic.

2, writing class scheduling

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/ / TestShedule.java import org.quartz .*; import java.util .*; public class TestShedule = (static SchedulerFactory schedFact new org.quartz. Impl.StdSchedulerFactory (); static Scheduler sched; public static void run () throws Exception (= schedFact.getScheduler sched () / / Get Scheduling Manager JobDetail jobDetail = new JobDetail ( "myJob" sched.DEFAULT_GROUP, DumbJob.class); / / create work CronTrigger trigger = new CronTrigger ( "myTrigger", "test "," 0 / 10 * * * *? "); / / create Trigger sched.scheduleJob (jobDetail, trigger); / / added to the scheduling manager in sched.start ();// start scheduling management of public) static void stop () throws Exception (sched.shutdown ();)) </ Td> </ tr> </ table>

The purpose of this call is set up the rules, and here I use the "0 / 10 * * * *?" Said that every 10 seconds once.

3, prepared by the start of services:

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/ / ServiceLoader.java import javax.servlet. ServletContextEvent; import javax.servlet. ServletContextListener; public class ServiceLoader implements ServletContextListener (public void contextInitialized (ServletContextEvent sce) (try (TestShedule.run ();) catch (Exception ex) (System. out.println (ex.getMessage ());)) public void contextDestroyed (ServletContextEvent sce) (try (TestShedule.stop ();) catch (Exception ex) (System.out.println (ex.getMessage ());) )) </ Td> </ tr> </ table>

Calling in contextInitialized TestShedule.run () start background task; contextDestroyed Calling TestShedule.stop () stop background tasks.

4, the deployment of such services launched

In web.xml file add the following line in the configuration:

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<? Xml version = "1.0" encoding = "UTF-8"> web-app PUBLIC "- / / Sun Microsystems, Inc / / DTD Web Application 2.3 / / EN" "http://java.sun.com / dtd/web-app_2_3.dtd "> Root ServiceLoader Index.html </ Td> </ tr> </ table>

5, web services can be launched.

Aggregate

In fact, the functions of the realization of this lot, I am here is the application interface and the ServletContextListener revenue api quartz, and hope that you can help the development. Function TempSave (ElementID) (CommentsPersistDiv.setAttribute ( "CommentContent" document.getElementById (ElementID). Value); CommentsPersistDiv.save ( "CommentXMLStore");) function Restore (ElementID) (CommentsPersistDiv.load ( "CommentXMLStore"); document . getElementById (ElementID). CommentsPersistDiv.getAttribute value = ( "CommentContent");) </ td> </ tr> <tr>

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