Spring boot中用于预加载&启动时执行的CommandLineRunner和ApplicationRunner

前言

CommandLineRunner和ApplicationRunner可以让任务在Spring boot程序启动时执行，这常用来做一些初始化的操作，如果有多个初始化操作，可以用@Order注解来排序，如果同时定义了CommandLineRunner和ApplicationRunner，排序时是并列的关系，@Order对他们同时起效。除了以类的形式出现，我们还可以定义返回值为CommandLineRunner和ApplicationRunner的方法，并且给方法上加上@Bean的注解。以方法定义的CommandLineRunner和ApplicationRunner会优先执行ApplicationRunner，并且@Bean注解的方法运行在之前提到的类执行之后。实现CommandLineRunner的类的run方法传参是可变String数组，实现ApplicationRunner的类的run方法传参是ApplicationArguments，而注解为@Bean的commandLineRunner和applicationRunner传参为ApplicationContext。

代码

package com.example.demo;

import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.ApplicationRunner;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

import java.util.Arrays;
import java.util.stream.Collectors;

@SpringBootApplication
public class DemoApplication {

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

	@Bean
	public CommandLineRunner commandLineRunner(ApplicationContext ctx) {
		return args -> {

			System.out.println("commandLineRunner方法检查一下Spring Boot提供的bean:");
			String[] beanNames = ctx.getBeanDefinitionNames();
			Arrays.sort(beanNames);
			for (String beanName : beanNames) {
				//System.out.println(beanName);
			}

		};
	}

	@Bean
	public ApplicationRunner applicationRunner(ApplicationContext ctx){
		return args -> {
			System.out.println("applicationRunner方法检查一下Spring Boot提供的bean:");
			String[] beanNames = ctx.getBeanDefinitionNames();
			Arrays.sort(beanNames);
			for (String beanName : beanNames) {
				//System.out.println(beanName);
			}
		};
	}

	@Component
	@Order(value = 1)
	public class MyStartupRunner1 implements CommandLineRunner{
		@Override
		public void run(String... strings) throws Exception {
			System.out.println(">>>>>>>>>>>>>>>服务启动执行，执行加载数据等操作 CommandLineRunner1 order 1 <<<<<<<<<<<<<");
		}
	}

	@Component
	@Order(value = 2)
	public class MyStartupRunner2 implements CommandLineRunner {
		@Override
		public void run(String... strings) throws Exception {
			String strArgs = Arrays.stream(strings).collect(Collectors.joining("|"));
			System.out.println(">>>>>>>>>>>>>>>服务启动执行，执行加载数据等操作 CommandLineRunner2 order 2 <<<<<<<<<<<<<"+strArgs);
		}
	}

	@Component  //此类一定要交给spring管理
	@Order(value=4) //首先执行
	public class ConsumerRunnerA implements ApplicationRunner {

		@Override
		public void run(ApplicationArguments args) throws Exception {
			System.out.println("需要在springBoot项目启动时执行的代码 ApplicationRunner order 4---");
		}
	}

	@Component  //此类一定要交给spring管理
	@Order(value=3) //其次执行
	public class ConsumerRunnerB implements ApplicationRunner{
		@Override
		public void run(ApplicationArguments args) throws Exception{

			//代码
			System.out.println("需要在springBoot项目启动时执行的代码 ApplicationRunner order 3---");
		}
	}
}

执行结果