CommandLineRunner、ApplicationRunner of SpringBoot

た入场券 2022-05-16 00:25 197阅读 0赞

如果需要在容器启动的时候就开始执行一些内容。比如配置初始化等，SpringBoot提供的这个接口就是干这个的。同时，通过其源码发现，它还提供了另外一个有同样功能的接口叫ApplicationRunner。两者的区别在于所接受的参数类型不一样。

CommandLineRunner的run方法定义如下：

/**
    	 * Callback used to run the bean.
    	 * @param args incoming main method arguments
    	 * @throws Exception on error
    	 */
    	void run(String... args) throws Exception;

而ApplicationRunner的定义如下：

/**
    	 * Callback used to run the bean.
    	 * @param args incoming application arguments
    	 * @throws Exception on error
    	 */
    	void run(ApplicationArguments args) throws Exception;

其他方面没什么区别。都是在容器启动时做指定动作。

简单使用示例：

@SpringBootApplication(exclude = {DataSourceAutoConfiguration.class})
    public class Application implements CommandLineRunner {
    
    	@Autowired
    	CollectorExecRateService collectorExecRateService;
    
    	public static void main(String[] args) {
    		SpringApplication.run(Application.class, args);
    	}
    
    	@Override
    	public void run(String... strings) throws Exception {
    		DefaultExports.initialize();
    		//do something you need
    	}
    }

**最后，对于CommandLineRunner中run方法的执行时机，是在Spring容器完全启动完成的时候被执行。**

看下源码中的说明：（ 源码位置：SpringApplication.run(String... args)，springboot版本：2.0.2 ）

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);
                //这里是去调用CommandLineRunner or ApplicationRunner的run方法
    			callRunners(context, applicationArguments);
    		}

callRunners的方法很简单，就是排序后执行run方法：

private void callRunners(ApplicationContext context, ApplicationArguments args) {
    		List<Object> runners = new ArrayList<>();
            //注册所有实现两个接口的class
    		runners.addAll(context.getBeansOfType(ApplicationRunner.class).values());
    		runners.addAll(context.getBeansOfType(CommandLineRunner.class).values());
    		//根据order排序
            AnnotationAwareOrderComparator.sort(runners);
            //遍历所有注册的方法，执行其内容
    		for (Object runner : new LinkedHashSet<>(runners)) {
    			if (runner instanceof ApplicationRunner) {
                    //执行ApplicationRunner中的run
    				callRunner((ApplicationRunner) runner, args);
    			}
    			if (runner instanceof CommandLineRunner) {
                    //执行CommandLineRunner中的run
    				callRunner((CommandLineRunner) runner, args);
    			}
    		}
    	}
    
    
        //执行ApplicationRunner
        private void callRunner(ApplicationRunner runner, ApplicationArguments args) {
    		try {
    			(runner).run(args);
    		}
    		catch (Exception ex) {
    			throw new IllegalStateException("Failed to execute ApplicationRunner", ex);
    		}
    	}
        //执行CommandLineRunner
    	private void callRunner(CommandLineRunner runner, ApplicationArguments args) {
    		try {
    			(runner).run(args.getSourceArgs());
    		}
    		catch (Exception ex) {
    			throw new IllegalStateException("Failed to execute CommandLineRunner", ex);
    		}
    	}