SpringBoot中CommandLineRunner接口起什么作用呢？

SpringBoot中CommandLineRunner接口的简介

springboot中应用服务启动时
   会加载一些数据和运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
    此时这些操作就可以借助CommandLineRunner接口的功能

注意事项:
     1.SpringBoot提供CommandLineRunner接口
	   当有该接口多个实现类时,提供了@order注解实现自定义执行顺序
	   也可以实现Ordered接口来自定义顺序。
     2.Ordered的数字越小,优先级越高,
	   也就是@Order(1)注解的类会在@Order(2)注解的类之前执行

package com.java265.init;

import com.java265.service.MyMethorClassService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

@Component
@Order(value=1)
public class SpringDataInit implements CommandLineRunner {

    @Autowired
    private MyMethorClassService myMethorClassService;

    @Override
    public void run(String... strings) throws Exception {
        int result = myMethorClassService.add(99, 777);
        System.out.println("----------SpringDataInit1---------"+result);
    }
}

 
package com.java265.init;

import com.java265.service.MyMethorClassService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

@Component
@Order(value=2)
public class SpringDataInit2 implements CommandLineRunner {

    @Autowired
    private MyMethorClassService myMethorClassService;

    @Override
    public void run(String... strings) throws Exception {
        int result = myMethorClassService.add(99, 777);
        System.out.println("----------SpringDataInit2---------"+result);
    }
}

SpringBoot提供的ApplicationRunner接口也可以满足该业务场景。不同点：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

package com.java265.init;

import com.java265.service.MyMethorClassService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.ApplicationRunner;
import org.springframework.core.Ordered;
import org.springframework.stereotype.Component;

@Component
//@Order(value=3)
public class SpringDataInit3 implements ApplicationRunner,Ordered {

    @Autowired
    private MyMethorClassService myMethorClassService;

    @Override
    public void run(ApplicationArguments applicationArguments) throws Exception {
        int result = myMethorClassService.add(10, 82);
        System.out.println("----------SpringDataInit3---------"+result);
    }

    @Override
    public int getOrder() {
        return 3;
    }
}

在Spring框架中,使用Applicationlistener接口也可以满足该业务场景

package com.java265.init;
import com.java265.service.MyMethorClassService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationListener;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.event.ContextRefreshedEvent;

@Configuration
public class SpringDoneDataInit implements ApplicationListener<ContextRefreshedEvent> {

    @Autowired
    private MyMethorClassService    myMethorClassService;

    @Override
    public void onApplicationEvent(ContextRefreshedEvent contextRefreshedEvent) {
        int result = myMethorClassService.add(5, 10);
        System.out.println("----------SpringDoneDataInit---------"+result);
    }
}

spring内置的事件

ContextRefreshedEvent:ApplicationContext容器初始化或者刷新时触发该事件
ContextStartedEvent:当使用ConfigurableApplicationContext接口的start()方法启动ApplicationContext容器时触发该事件
ContextClosedEvent:当使用ConfigurableApplicationContext接口的close()方法关闭ApplicationContext容器时触发该事件
ContextStopedEvent:
      当使用ConfigurableApplicationContext接口的stop()方法停止ApplicationContext容器时触发该事件