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应用启动数据初始化接口CommandLineRunner和Application详解

2021-12-21 18:54:29 来源:易采站长站 作者:

应用启动数据初始化接口CommandLineRunner和Application详解,接口,参数,初始化,顺序,方法

应用启动数据初始化接口CommandLineRunner和Application详解

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目录
应用启动数据初始化接口CommandLineRunner和Application详解1 运行时机2 实现接口3 执行顺序4 设置启动参数5 运行效果ApplicationRunner和CommandLineRunner用法区别ApplicationRunnerCommandLineRunner

应用启动数据初始化接口CommandLineRunner和Application详解

在SpringBoot项目中创建组件类实现CommandLineRunner或ApplicationRunner接口可实现在应用启动之后及时进行一些初始化操作,如缓存预热、索引重建等等类似一些数据初始化操作。

两个接口功能相同,都有个run方法需要重写,只是实现方法的参数不同。

CommandLineRunner接收原始的命令行启动参数,ApplicationRunner则将启动参数对象化。

1 运行时机

两个接口都是在SpringBoot应用初始化好上下文之后运行,所以在运行过程中,可以使用上下文中的所有信息,例如一些Bean等等。在框架SpringApplication类源码的run方法中,可查看Runner的调用时机callRunners,如下:

/**
 * Run the Spring application, creating and refreshing a new
 * [email protected] ApplicationContext}.
 * @param args the application arguments (usually passed from a Java main method)
 * @return a running [email protected] ApplicationContext}
 */
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);
		//调用Runner,执行初始化操作
		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 实现接口

2.1 CommandLineRunner

简单实现如下,打印启动参数信息:

@Order(1)
@Component
public class CommandLineRunnerInit implements CommandLineRunner {
    private Logger logger = LoggerFactory.getLogger(this.getClass());
    private final String LOG_PREFIX = ">>>>>>>>>>CommandLineRunner >>>>>>>>>> ";
    @Override
    public void run(String... args) throws Exception {
        try {
            this.logger.error("{} args:{}", LOG_PREFIX, StringUtils.join(args, ","));
        } catch (Exception e) {
            logger.error("CommandLineRunnerInit run failed", e);
        }
    }
}

2.2 ApplicationRunner

简单实现如下,打印启动参数信息,并调用Bean的方法(查询用户数量):

@Order(2)
@Component
public class ApplicationRunnerInit implements ApplicationRunner {
    private Logger logger = LoggerFactory.getLogger(this.getClass());
    private final String LOG_PREFIX = ">>>>>>>>>>ApplicationRunner >>>>>>>>>> ";
    private final UserRepository userRepository;
    public ApplicationRunnerInit(UserRepository userRepository) {
        this.userRepository = userRepository;
    }
    @Override
    public void run(ApplicationArguments args) throws Exception {
        try {
            this.logger.error("{} args:{}", LOG_PREFIX, JSONObject.toJSONString(args));
            for (String optionName : args.getOptionNames()) {
                this.logger.error("{} argName:{} argValue:{}", LOG_PREFIX, optionName, args.getOptionValues(optionName));
            }
            this.logger.error("{} user count:{}", LOG_PREFIX, this.userRepository.count());
        } catch (Exception e) {
            logger.error("CommandLineRunnerInit run failed", e);
        }
    }
}

3 执行顺序

如果实现了多个Runner,默认会按照添加顺序先执行ApplicationRunner的实现再执行CommandLineRunner的实现,如果多个Runner之间的初始化逻辑有先后顺序,[email protected],可在源码SpringApplication类的callRunners方法中查看,如下:

private void callRunners(ApplicationContext context, ApplicationArguments args) {
 List<Object> runners = new ArrayList<>();
 //先添加的ApplicationRunner实现
 runners.addAll(context.getBeansOfType(ApplicationRunner.class).values());
 //再添加的CommandLineRunner实现
 runners.addAll(context.getBeansOfType(CommandLineRunner.class).values());
 //如果设置了顺序,则按设定顺序重新排序
 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);
  }
 }
}

4 设置启动参数

为了便于对比效果,在Idea中设置启动参数如下图(生产环境中会自动读取命令行启动参数):

在这里插入图片描述

5 运行效果

在上面的两个Runner中,设定了CommandLineRunnerInit是第一个,ApplicationRunnerInit是第二个。启动应用,运行效果如下图:

在这里插入图片描述

ApplicationRunner和CommandLineRunner用法区别

业务场景:

应用服务启动时,加载一些数据和执行一些应用的初始化动作。如:删除临时文件,清除缓存信息,读取配置文件信息,数据库连接等。

1、SpringBoot提供了CommandLineRunner和ApplicationRunner接口。当接口有多个实现类时,[email protected],也可以实现Ordered接口来自定义顺序。

注意:数字越小,优先级越高,[email protected](1)[email protected](2)注解的类之前执行。

两者的区别在于:

ApplicationRunner中run方法的参数为ApplicationArguments,而CommandLineRunner接口中run方法的参数为String数组。想要更详细地获取命令行参数,那就使用ApplicationRunner接口

ApplicationRunner

@Component
@Order(value = 10)
public class AgentApplicationRun2 implements ApplicationRunner {
 @Override
 public void run(ApplicationArguments applicationArguments) throws Exception {
 }
}

CommandLineRunner

@Component
@Order(value = 11)
public class AgentApplicationRun implements CommandLineRunner {
 @Override
 public void run(String... strings) throws Exception {
 }
}

以上为个人经验,希望能给大家一个参考,也希望大家多多支持易采站长站。

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