在前面的例子中，我们配置的任务都是在项目启动的时候自动运行，我们也可以通过JobLauncher或者JobOperator手动控制任务的运行时机，这节记录下它们的用法。

框架搭建

新建一个Spring Boot项目，版本为2.2.4.RELEASE，artifactId为spring-batch-launcher，项目结构如下图所示：

Spring Batch任务调度 - 图1

剩下的数据库层的准备，项目配置，依赖引入和Spring Batch入门文章中的框架搭建步骤一致，这里就不再赘述。

此外，本节我们需要演示在Controller里通过JobLauncher或者JobOperator调度任务，所以我们还需在pom里引入web依赖：

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

然后准备个任务，用于后续测试。在cc.mrbird.batch包下新建job包，然后在该包下新建MyJob：

@Component
public class MyJob{
    @Autowired
    private JobBuilderFactory jobBuilderFactory;
    @Autowired
    private StepBuilderFactory stepBuilderFactory;
    @Bean
    public Job job(){
        return jobBuilderFactory.get("job")
                .start(step())
                .build();
    }
    private Step step(){
        return stepBuilderFactory.get("step")
                .tasklet((stepContribution, chunkContext) -> {
                    StepExecution stepExecution = chunkContext.getStepContext().getStepExecution();
                    Map<String, JobParameter> parameters = stepExecution.getJobParameters().getParameters();
                    System.out.println(parameters.get("message").getValue());
                    return RepeatStatus.FINISHED;
                })
                .listener(this)
                .build();
    }
}

在step()方法中，我们通过执行上下文获取了key为message的参数值。

JobLauncher

在cc.mrbird.batch包下新建controller包，然后在该包下新建JobController：

@RestController
@RequestMapping("job")
public class JobController {
    @Autowired
    private Job job;
    @Autowired
    private JobLauncher jobLauncher;
    @GetMapping("launcher/{message}")
    public String launcher(@PathVariable String message) throws Exception {
        JobParameters parameters = new JobParametersBuilder()
                .addString("message", message)
                .toJobParameters();
        // 将参数传递给任务
        jobLauncher.run(job, parameters);
        return "success";
    }
}

上面代码中，我们注入了JobLauncher和上面配置的Job，然后通过JobLauncher的run(Job job, JobParameters jobParameters)方法运行指定的任务Job，并且传递了参数。

要关闭Spring Batch启动项目自动运行任务的机制，需要在项目配置文件application.yml中添加如下配置：

spring:
  batch:
    job:
      enabled: false

启动项目，在浏览器地址栏访问：http://localhost:8080/job/launcher/hello：

Spring Batch任务调度 - 图2

项目控制台日志打印如下：

2020-03-12 10:24:31.547  INFO 41266 --- [nio-8080-exec-4] o.s.b.c.l.support.SimpleJobLauncher      : Job: [SimpleJob: [name=job]] launched with the following parameters: [{message=hello}]
2020-03-12 10:24:31.583  INFO 41266 --- [nio-8080-exec-4] o.s.batch.core.job.SimpleStepHandler     : Executing step: [step]
hello
2020-03-12 10:24:31.610  INFO 41266 --- [nio-8080-exec-4] o.s.batch.core.step.AbstractStep         : Step: [step] executed in 27ms
2020-03-12 10:24:31.632  INFO 41266 --- [nio-8080-exec-4] o.s.b.c.l.support.SimpleJobLauncher      : Job: [SimpleJob: [name=job]] completed with the following parameters: [{message=hello}] and the following status: [COMPLETED] in 76ms

此外，需要注意的是：同样的参数，同样的任务再次运行的时候将抛出JobInstanceAlreadyCompleteException异常，比如在浏览器中再次访问http://localhost:8080/job/launcher/hello，项目控制台日志打印如下：

org.springframework.batch.core.repository.JobInstanceAlreadyCompleteException: A job instance already exists and is complete for parameters={message=hello}.  If you want to run this job again, change the parameters.
    at org.springframework.batch.core.repository.support.SimpleJobRepository.createJobExecution(SimpleJobRepository.java:131) ~[spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_231]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_231]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_231]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_231]
    at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:344) ~[spring-aop-5.2.4.RELEASE.jar:5.2.4.RELEASE]
    ...

所以我们在任务调度的时候，应避免参数重复。

JobOperator

在JobController里添加一个新的端点：

@RestController
@RequestMapping("job")
public class JobController {
    @Autowired
    private JobOperator jobOperator;
    @GetMapping("operator/{message}")
    public String operator(@PathVariable String message) throws Exception {
        // 传递任务名称，参数使用 kv方式
        jobOperator.start("job", "message=" + message);
        return "success";
    }
}

上面代码中，我们注入了JobOperator，JobOperator的start(String jobName, String parameters)方法传入的是任务的名称（任务在Spring IOC容器中的名称）,并且参数使用key-value的方式传递。

要通过任务名称获取到相应的Bean，还需要添加一个额外的配置。在cc.mrbird.batch包下新建configure包，然后在该包下新建JobConfigure：

@Configuration
public class JobConfigure {
    /**
     * 注册JobRegistryBeanPostProcessor bean
     * 用于将任务名称和实际的任务关联起来
     */
    @Bean
    public JobRegistryBeanPostProcessor processor(JobRegistry jobRegistry, ApplicationContext applicationContext) {
        JobRegistryBeanPostProcessor postProcessor = new JobRegistryBeanPostProcessor();
        postProcessor.setJobRegistry(jobRegistry);
        postProcessor.setBeanFactory(applicationContext.getAutowireCapableBeanFactory());
        return postProcessor;
    }
}

如果没有这段配置，在任务调度的时候将报org.springframework.batch.core.launch.NoSuchJobException: No job configuration with the name [job] was registered。

启动任务，浏览器访问：http://localhost:8080/job/operator/mrbird：

Spring Batch任务调度 - 图3

项目控制台日志打印如下：

2020-03-12 10:51:20.174  INFO 41405 --- [nio-8080-exec-2] o.s.b.c.l.support.SimpleJobOperator      : Checking status of job with name=job
2020-03-12 10:51:20.183  INFO 41405 --- [nio-8080-exec-2] o.s.b.c.l.support.SimpleJobOperator      : Attempting to launch job with name=job and parameters=message=mrbird
2020-03-12 10:51:20.239  INFO 41405 --- [nio-8080-exec-2] o.s.b.c.l.support.SimpleJobLauncher      : Job: [SimpleJob: [name=job]] launched with the following parameters: [{message=mrbird}]
2020-03-12 10:51:20.293  INFO 41405 --- [nio-8080-exec-2] o.s.batch.core.job.SimpleStepHandler     : Executing step: [step]
mrbird
2020-03-12 10:51:20.324  INFO 41405 --- [nio-8080-exec-2] o.s.batch.core.step.AbstractStep         : Step: [step] executed in 31ms
2020-03-12 10:51:20.344  INFO 41405 --- [nio-8080-exec-2] o.s.b.c.l.support.SimpleJobLauncher      : Job: [SimpleJob: [name=job]] completed with the following parameters: [{message=mrbird}] and the following status: [COMPLETED] in 83ms

JobOperator包含了许多实用的方法：

Spring Batch任务调度 - 图4

具体可以自己尝试玩一玩。