SpringBatch 之 spring.batch.job.enabled

spring.batch.job.enabled 配置用于启动时是否创建JobLauncherCommandLineRunner, 若spring.batch.job.enabled=true, 则会创建JobLauncherCommandLineRunner实例并且执行。spring.batch.job.enabled=false则不会创建实例。那SpringBoot是如何做到的呢？

首先，如何自动创建JobLauncherCommandLineRunner，在源码中找到BatchAutoConfiguration这个类，然后可以找到jobLauncherCommandLineRunner， 这个方法就是用于创建JobLauncherCommandLineRunner实例。可以看到创建该实例的条件是不存在相同的bean并且spring.batch.job.enabled=true，若不存在spring.batch.job.enabled默认创建。

 @Bean
    @ConditionalOnMissingBean
    @ConditionalOnProperty(
        prefix = "spring.batch.job",
        name = {"enabled"},
        havingValue = "true",
        matchIfMissing = true
    )
    public JobLauncherCommandLineRunner jobLauncherCommandLineRunner(JobLauncher jobLauncher, JobExplorer jobExplorer) {
        JobLauncherCommandLineRunner runner = new JobLauncherCommandLineRunner(jobLauncher, jobExplorer);
        String jobNames = this.properties.getJob().getNames();
        if (StringUtils.hasText(jobNames)) {
            runner.setJobNames(jobNames);
        }

        return runner;
    }

找到了创建bean的地方，那它是如何自动执行的run方法的呢？我们都知道，运行SpringBoot项目，我们可以通过SpringApplication.run(Object source, String… args)，在SpringApplication中会执行run方法， run方法中会调用afterRefresh方法，最终会调用callRunners方法，在这里可以看到，默认执行了ApplicationRunner和CommandLineRunner的run方法，而JobLauncherCommandLineRunner正是实现了CommandLineRunner接口。最终执行了JobLauncherCommandLineRunner的run方法。

public ConfigurableApplicationContext run(String... args) {
        StopWatch stopWatch = new StopWatch();
        stopWatch.start();
        ConfigurableApplicationContext context = null;
        FailureAnalyzers analyzers = null;
        this.configureHeadlessProperty();
        SpringApplicationRunListeners listeners = this.getRunListeners(args);
        listeners.starting();

        try {
            ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
            ConfigurableEnvironment environment = this.prepareEnvironment(listeners, applicationArguments);
            Banner printedBanner = this.printBanner(environment);
            context = this.createApplicationContext();
            new FailureAnalyzers(context);
            this.prepareContext(context, environment, listeners, applicationArguments, printedBanner);
            this.refreshContext(context);
            this.afterRefresh(context, applicationArguments);
            listeners.finished(context, (Throwable)null);
            stopWatch.stop();
            if (this.logStartupInfo) {
                (new StartupInfoLogger(this.mainApplicationClass)).logStarted(this.getApplicationLog(), stopWatch);
            }

            return context;
        } catch (Throwable var9) {
            this.handleRunFailure(context, listeners, (FailureAnalyzers)analyzers, var9);
            throw new IllegalStateException(var9);
        }
    }
    protected void afterRefresh(ConfigurableApplicationContext context, ApplicationArguments args) {
        this.callRunners(context, args);
    }

    private void callRunners(ApplicationContext context, ApplicationArguments args) {
        List<Object> runners = new ArrayList();
        runners.addAll(context.getBeansOfType(ApplicationRunner.class).values());
        runners.addAll(context.getBeansOfType(CommandLineRunner.class).values());
        AnnotationAwareOrderComparator.sort(runners);
        Iterator var4 = (new LinkedHashSet(runners)).iterator();

        while(var4.hasNext()) {
            Object runner = var4.next();
            if (runner instanceof ApplicationRunner) {
                this.callRunner((ApplicationRunner)runner, args);
            }

            if (runner instanceof CommandLineRunner) {
                this.callRunner((CommandLineRunner)runner, args);
            }
        }

    }