1. 简介

SpringCloud任务允许用户使用SpringCloud开发和运行短期的微服务，在本地 、云环境中、甚至在SpringCloud Data Flow上运行它们。仅添加注解@EnableTask便可将app作为spring boot app运行。
spring cloud task让创建短期的微服务变得很容易。它提供的功能允许在生产环境中按需执行短期的JVM进程。

2. 环境要求

Java8级更高版本
spring cloud task使用RDB来存储任务运行的结果，当然开发的时候也可以不适用数据库，任务的状态作为taskrepository更新的一部分进行记录。目前支持的RDB有：

• DB2
• H2
• HSQLDB
• MySql
• Oracle
• Postgres
• SqlServer

3. Spring Cloud Task之Hello World

Hello World
引入依赖

<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-task</artifactId>
		</dependency>

启动类

@SpringBootApplication(scanBasePackages = {"com.yuyan"})
@ComponentScan({"com.yuyan"})
@EnableTask
public class StarterApplication {

	private static final Logger log = LoggerFactory.getLogger(StarterApplication.class);

	public static void main(String[] args) {
		SpringApplication.run(StarterApplication.class, args);
	}
	
	@Bean
	public CommandLineRunner commandLineRunner() {
		return new HelloWorldCommandLineRunner();
	}

	public static class HelloWorldCommandLineRunner implements CommandLineRunner {

		@Override
		public void run(String... strings) throws Exception {
			log.info("running a task!!!!");
		}
	}
}

application.properties

spring.application.name=task1

logging.level.org.springframework.cloud.task=DEBUG

CommandLineRunner

@EnableTask
这个类级注解用来开启Spring Cloud Task的功能。默认情况下，会引入一个附加的配置类SimpleTaskConfiguration，这个附加的配置会注册taskrepository和基础资源以供使用。
TaskRepository使用内存的Map来保存Task执行的结果。这个Map在生产环境中并不是有效的解决方案，因为这个Map会随着任务的结束而销毁。
CommandLineRunner

SimpleTaskRepository
默认任务仓库

4. 生命周期

实现接口TaskExecutionListener监听任务的状态

@Component
public class MyTaskListener implements TaskExecutionListener {

    private static final Logger log = LoggerFactory.getLogger(MyTaskListener.class);


    @Override
    public void onTaskStartup(TaskExecution taskExecution) {
        log.info("starting task:" + taskExecution.getTaskName());
    }

    @Override
    public void onTaskEnd(TaskExecution taskExecution) {
        log.info("ending task:" + taskExecution.getTaskName());
    }

    @Override
    public void onTaskFailed(TaskExecution taskExecution, Throwable throwable) {
        log.info("task failed:" + taskExecution.getTaskName());
        log.error("error msg:", throwable);
    }
}

5. 为任务配置数据源

引入jpa的依赖

<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-data-jpa</artifactId>
		</dependency>

修改application.properties

spring.datasource.driver-class-name=org.postgresql.Driver
spring.datasource.url=jdbc:postgresql://127.0.0.1:5432/test?useUnicode=true&characterEncoding=UTF-8
spring.datasource.username=postgres
spring.datasource.password=root

spring.jpa.show-sql=true
spring.jpa.hibernate.ddl-auto=update
spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.PostgreSQLDialect
spring.jpa.properties.hibernate.temp.use_jdbc_metadata_defaults = false
spring.jackson.serialization.indent-output=false

为TaskConfigurer配置数据源

@Autowired
    private DataSource dataSource;

    @Bean
    public DefaultTaskConfigurer getTaskConfigurer() {
        return new DefaultTaskConfigurer(dataSource);
    }

运行task之后数据库中增加如下四张表

task_execution记录了刚刚任务执行的起始时间、结果等数据

6. 集成Spring Batch

引入spring batch依赖

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-batch</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-task-batch</artifactId>
		</dependency>

application.properties中增加

spring.batch.initialize-schema=always

JobConfiguration

    @Autowired
    public JobBuilderFactory jobBuilderFactory;

    @Autowired
    public StepBuilderFactory stepBuilderFactory;
    
    @Bean
    public Job job1() {
        return this.jobBuilderFactory.get("job1")
                .start(this.stepBuilderFactory.get("job1step1")
                        .tasklet(new Tasklet() {
                            @Override
                            public RepeatStatus execute(StepContribution contribution, ChunkContext chunkContext) throws Exception {
                                logger.info("Job1 was run");
                                return RepeatStatus.FINISHED;
                            }
                        })
                        .build())
                .build();
    }

Spring Batch的东西远不止这些。。。

7. 任务实例个数的限制

引入依赖

		<dependency>
			<groupId>org.springframework.integration</groupId>
			<artifactId>spring-integration-core</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework.integration</groupId>
			<artifactId>spring-integration-jdbc</artifactId>
		</dependency>

spring.cloud.task.single-instance-enabled为true表示同一个时刻只能有一个叫这个名字的task执行，否则会抛出Task with name “application” is already running.

#限制同一个时刻只能有一个同名任务执行
spring.cloud.task.single-instance-enabled=true