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This article introduces the knowledge of "how springboot creates scheduled tasks through annotations and interfaces". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Creation of scheduled tasks in springboot

There are two main ways to create springboot scheduled tasks.

Create by annotations

Implemented through the interfaces provided in springboot

Springboot creates scheduled tasks through annotations

First, pom is introduced.

The @ EnableScheduling annotation is mainly used in the class, all under the package org.springframework:spring-context.

You can use it by introducing org.springframework:spring-context as a package.

Org.springframework spring-context ${spring.version} directly into the code to a chestnut import org.springframework.scheduling.annotation.EnableScheduling;import org.springframework.scheduling.annotation.Scheduled;import org.springframework.stereotype.Component;import java.text.SimpleDateFormat;import java.util.Date;/** * @ createdTime: 16:00 on 2020-4-7. * @ version: 1.0. * / / use @ EnableScheduling to open the timed task @ Component@EnableSchedulingpublic class TestTask {private static ThreadLocal dateFormat = ThreadLocal.withInitial (()-> new SimpleDateFormat ("yyyy-MM-dd HH:mm:ss")) on the type; / / use the @ Scheduled annotation on the method to create a specific timed task @ Scheduled (cron = "0 Scheduled 10 *?") Private void task1 () {System.err.println ("scheduled task is executed, execution time is:" + dateFormat.get () .format (new Date ();}}

Take a look at the execution result:

@ EnableScheduling is used on the class to start timing tasks, and @ Component is used to inject into the spring container. I have not tried whether @ Component will be injected here.

For the specific methods that need to be executed regularly, use the @ Scheduled annotation. There are many parameters in this annotation. I use the cron expression here. Let's introduce the parameters of this annotation.

Parameters of @ Scheduled annotation

Cron

How to use: @ Scheduled (cron = "0ax 10 *?")

Source code definition: String cron () default ""

Description: the cron expression, which is our daily cron, will not be posted.

Zone

How to use: @ Scheduled (zone = "GMT+08:00")

Source code definition: String zone () default ""

Description: time zone, cron expression will be parsed based on this time zone. The default is empty, and it will take the time zone of the server where the application is located. Generally, it is OK to leave it empty, and the TimeZone in jdk uses a unified system, so don't be specific.

FixedDelay

How to use: @ Scheduled (fixedDelay = 1)

Source code definition: long fixedDelay () default-1

Description: after the last execution, how long will it take before execution, in milliseconds

FixedDelayString

Mode of use:

@ Scheduled (fixedDelayString = "1")

@ Scheduled (fixedDelayString = "${values in the configuration file}")

Source code definition: String fixedDelayString () default ""

Description: like fixedDelay, the string type can be filled in milliseconds, and the values in the configuration file can be used in the same way as the spring injection configuration file.

FixedRate

How to use: @ Scheduled (fixedRate = 1)

Source code definition: long fixedRate () default-1

Description: how often will it be executed after the start of the last execution, in milliseconds?

FixedRateString

Mode of use:

@ Scheduled (fixedRateString = "1")

@ Scheduled (fixedRateString = "${values in the configuration file}")

Source code definition: String fixedRateString () default ""

Description: like fixedRate, the string type can be filled in milliseconds, and the values in the configuration file can be used in the same way as the spring injection configuration file.

InitialDelay

How to use: @ Scheduled (initialDelay = 1)

Source code definition: long initialDelay () default-1

Description: how often will it be executed after the last execution, in milliseconds?

InitialDelayString

Mode of use:

@ Scheduled (initialDelayString = "1")

@ Scheduled (initialDelayString = "${values in the configuration file}")

Source code definition: String initialDelayString () default ""

Description: like initialDelay, the string type can be filled in milliseconds, and the values in the configuration file can be used in the same way as the spring injection configuration file.

Springboot creates scheduled tasks through the note interface.

Creating timing through the interface will be more flexible, and the timing cron expression does not have to be written on the comments of the code, but can be stored in a storage system such as a database, and the expression of this configuration can be obtained in the interface. In this way, a simple task scheduling platform can be implemented, and the execution of timing tasks can be managed through database configuration.

Implement interface SchedulingConfigurer

This interface SchedulingConfigurer is mainly used. It is the package path of org.springframework.scheduling.annotation.SchedulingConfigurer. In fact, it is all under the package org.springframework:spring-context.

You can use it by introducing org.springframework:spring-context as a package.

Org.springframework spring-context ${spring.version} main methods

Override the configureTasks method, which adds timed tasks through ScheduledTaskRegistrar. Roughly speaking, the input parameter is basically a thread object, and the latter parameter is the same as in the annotation. There are mainly cron expressions. After the last execution of delay, how much time will it take to execute it? initial and so on will not be repeated.

Go straight to the code and give me a chestnut.

Import org.springframework.scheduling.TaskScheduler;import org.springframework.scheduling.annotation.EnableScheduling;import org.springframework.scheduling.annotation.SchedulingConfigurer;import org.springframework.scheduling.config.ScheduledTaskRegistrar;import org.springframework.scheduling.config.Task;import org.springframework.stereotype.Component;import java.text.SimpleDateFormat;import java.util.Date;/** * @ createdTime: 18:33 on 2020-4-7. * @ version: 1.0. * / @ Component@EnableSchedulingpublic class TestTask2 implements SchedulingConfigurer {private static ThreadLocal dateFormat = ThreadLocal.withInitial (()-> new SimpleDateFormat ("yyyy-MM-dd HH:mm:ss")); / * * Callback allowing a {@ link TaskScheduler * TaskScheduler} and specific {@ link Task Task} * instances to be registered against the given the {@ link ScheduledTaskRegistrar}. * * @ param taskRegistrar the registrar to be configured. * / @ Override public void configureTasks (ScheduledTaskRegistrar taskRegistrar) {System.err.println ("pretending to get a configured scheduled task execution plan from the database"); String cron = "0ram 10 *?" TaskRegistrar.addCronTask (()-> {System.err.println ("API timed task executes scheduled task, execution time is" + dateFormat.get () .format (new Date ();}, cron);}}

Here, by rewriting the configureTasks method, using the ScheduledTaskRegistrar object to create a scheduled task, and then the expression can be read from the database and other places, the code will not be written during the demonstration, so a simple task scheduling platform can be easily implemented.

Take a look at the execution result:

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