使用CommandLineRunner和ApplicationRunner接口及其源码分析

一 、使用实例

　　1.1  CommandLineRunner接口

　　使用CommandLineRunner接口类似于Main方法启动，可以接受一个字符串数组的命令行参数，以下为具体实现：

@Component
public class MyCommandLineRunner implements CommandLineRunner{

    @Override
    public void run(String... args) throws Exception{
        //假装有代码
    }
}

　　1.2 ApplicationRunner 接口

　　此种方式与实现CommandLineRunner接口的区别就是他的参数是ApplicationArguments。

@Order(value = 1)
@Component
public class MyApplicationRunner implements ApplicationRunner{

    @Override
    public void run(ApplicationArguments args) throws Exception{
        //假装有代码
    }
}

二、源码分析

　　2.1 主程序启动

 public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

　　2.2  ConfigurableApplicationContext run(String... args)方法

　　调用以下方法，完成容器的初始化和其他必要的操作之后，执行callRunners(context, applicationArguments)方法。

public ConfigurableApplicationContext run(String... args) {
        StopWatch stopWatch = new StopWatch();
        stopWatch.start();
        ConfigurableApplicationContext context = null;
        Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();
        configureHeadlessProperty();
        SpringApplicationRunListeners listeners = getRunListeners(args);
        listeners.starting();
        try {
            ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
            ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments);
            configureIgnoreBeanInfo(environment);
            Banner printedBanner = printBanner(environment);
            context = createApplicationContext();
            exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,
                    new Class[] { ConfigurableApplicationContext.class }, context);
            prepareContext(context, environment, listeners, applicationArguments, printedBanner);
            refreshContext(context);
            afterRefresh(context, applicationArguments);
            stopWatch.stop();
            if (this.logStartupInfo) {
                new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);
            }
            listeners.started(context);
            callRunners(context, applicationArguments);
        }
        catch (Throwable ex) {
            handleRunFailure(context, ex, exceptionReporters, listeners);
            throw new IllegalStateException(ex);
        }

        try {
            listeners.running(context);
        }
        catch (Throwable ex) {
            handleRunFailure(context, ex, exceptionReporters, null);
            throw new IllegalStateException(ex);
        }
        return context;
    }

 2.3 callRunners方法

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());
　　　　　　// 根据优先级进行排序，其中ApplicationRuner.class和CommandLineRunner.class混合在一起进行排序。
        AnnotationAwareOrderComparator.sort(runners);
        for (Object runner : new LinkedHashSet<>(runners)) {
            if (runner instanceof ApplicationRunner) {
                callRunner((ApplicationRunner) runner, args);
            }
            if (runner instanceof CommandLineRunner) {
                callRunner((CommandLineRunner) runner, args);
            }
        }
    }