Spring Boot - ApplicationRunner && CommandLineRunner扩展接口

文章目录

• Pre
• org.springframework.boot.CommandLineRunner
• 使用场景
• 源码解析
• 扩展示例
  • ApplicationRunner
  • CommandLineRunner

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Pre

Spring Boot - 扩展接口一览

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org.springframework.boot.CommandLineRunner

代码语言：javascript复制

/**
 * Interface used to indicate that a bean should <em>run</em> when it is contained within
 * a {@link SpringApplication}. Multiple {@link CommandLineRunner} beans can be defined
 * within the same application context and can be ordered using the {@link Ordered}
 * interface or {@link Order @Order} annotation.
 * <p>
 * If you need access to {@link ApplicationArguments} instead of the raw String array
 * consider using {@link ApplicationRunner}.
 *
 * @author Dave Syer
 * @since 1.0.0
 * @see ApplicationRunner
 */
@FunctionalInterface
public interface CommandLineRunner {

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

}

接口也只有一个方法：run(String... args)

如果有多个CommandLineRunner，可以利用@Order来进行排序, 按照@Order中的value值从小到大依次执行。

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使用场景

• 触发时机为整个项目启动完毕后（执行时机为容器启动完成的时候），自动执行。
• 扩展此接口，进行启动项目之后一些业务的预处理。

---

源码解析

代码语言：javascript复制

	/**
	 * Run the Spring application, creating and refreshing a new
	 * {@link ApplicationContext}.
	 * @param args the application arguments (usually passed from a Java main method)
	 * @return a running {@link ApplicationContext}
	 */
	public ConfigurableApplicationContext run(String... args) {
	    // 创建并启动计时监控类
		StopWatch stopWatch = new StopWatch();
		stopWatch.start();
		DefaultBootstrapContext bootstrapContext = createBootstrapContext();
		ConfigurableApplicationContext context = null;
		configureHeadlessProperty();
		// 创建所有 Spring 运行监听器并发布应用启动事件
		SpringApplicationRunListeners listeners = getRunListeners(args);
		listeners.starting(bootstrapContext, this.mainApplicationClass);
		try {
		    // 处理 args 参数
			ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
			
			// 准备环境
			ConfigurableEnvironment environment = prepareEnvironment(listeners, bootstrapContext, applicationArguments);
			configureIgnoreBeanInfo(environment);
			
			Banner printedBanner = printBanner(environment);
			// 创建应用上下文
			context = createApplicationContext();
			context.setApplicationStartup(this.applicationStartup);
			// 准备应用上下文
			prepareContext(bootstrapContext, context, environment, listeners, applicationArguments, printedBanner);
			// 刷新应用上下文
			refreshContext(context);
			// 应用上下文刷新之后的事件的处理
			afterRefresh(context, applicationArguments);
			stopWatch.stop();
			if (this.logStartupInfo) {
				new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);
			}
			// 发布应用上下文启动完成事件
			listeners.started(context);]
			// 执行所有 Runner 运行器
			callRunners(context, applicationArguments);
		}
		catch (Throwable ex) {
			handleRunFailure(context, ex, listeners);
			throw new IllegalStateException(ex);
		}

		try {
			
			 // 发布应用上下文就绪事件
			listeners.running(context);
		}
		catch (Throwable ex) {
			handleRunFailure(context, ex, null);
			throw new IllegalStateException(ex);
		}
		return context;
	}

继续 this.callRunners(context, applicationArguments);

核心方法 callRunners

代码语言：javascript复制

private void callRunners(ApplicationContext context, ApplicationArguments args) {
		//将实现ApplicationRunner和CommandLineRunner接口的类，存储到集合中
		List<Object> runners = new ArrayList<>();
		// 从Spring容器中查找类型为ApplicationRunner的Bean
		runners.addAll(context.getBeansOfType(ApplicationRunner.class).values());
		// 从Spring容器中查找类型为CommandLineRunner的Bean
		runners.addAll(context.getBeansOfType(CommandLineRunner.class).values());
		
		 //按照加载先后顺序排序
		AnnotationAwareOrderComparator.sort(runners);
		
		//调用执行
		for (Object runner : new LinkedHashSet<>(runners)) {
			//如果是ApplicationRunner的实例
			if (runner instanceof ApplicationRunner) {
				callRunner((ApplicationRunner) runner, args);
			}
			 //如果是CommandLineRunner的实例
			if (runner instanceof CommandLineRunner) {
				callRunner((CommandLineRunner) runner, args);
			}
		}
	}

代码语言：javascript复制

private void callRunner(ApplicationRunner runner, ApplicationArguments args) {
		try {
			//调用各个实现类中的逻辑实现
			(runner).run(args);
		}
		catch (Exception ex) {
			throw new IllegalStateException("Failed to execute ApplicationRunner", ex);
		}
	}

OK， CLEAR

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扩展示例

ApplicationRunner

代码语言：javascript复制

package com.artisan.bootspringextend.testextends;

import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.ApplicationRunner;
import org.springframework.context.annotation.Configuration;

/**
 * @author 小工匠
 * @version 1.0
 * @description: TODO
 * @date 2022/12/7 11:49
 * @mark: show me the code , change the world
 */

@Slf4j
@Configuration
public class ExtendApplicationRunner implements ApplicationRunner {
    @Override
    public void run(ApplicationArguments args) throws Exception {
        log.info(">>>>>>>ExtendApplicationRunner#run called {}",args);

    }
}

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CommandLineRunner

代码语言：javascript复制

package com.artisan.bootspringextend.testextends;

import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.CommandLineRunner;
import org.springframework.context.annotation.Configuration;

/**
 * @author 小工匠
 * @version 1.0
 * @description: TODO
 * @date 2022/12/7 9:01
 * @mark: show me the code , change the world
 */

@Slf4j
@Configuration
public class ExtendCommandLineRunner  implements CommandLineRunner {
    @Override
    public void run(String... args) throws Exception {
        log.info(">>>>>>>ExtendCommandLineRunner#run called {}",args);
    }
}

spring

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