SpringBoot之CommandLineRunner接口

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。

注意：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。

[code]package com.example.studySpringBoot.init;

import com.example.studySpringBoot.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(8, 56);
System.out.println("----------SpringDataInit1---------"+result);
}
}

[code]
package com.example.studySpringBoot.init;

import com.example.studySpringB
4000
oot.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(10, 82);
System.out.println("----------SpringDataInit2---------"+result);
}
}

2、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

[code]package com.example.studySpringBoot.init;

import com.example.studySpringBoot.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;
}
}

3、如果使用了Spring框架，则使用ApplicationListener接口也可以满足该业务场景。

[code]package com.example.studySpringBoot.init;

import com.example.studySpringBoot.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

1. 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。
2. ContextClosedEvent：当使用ConfigurableApplicationContext接口的close()方法关闭ApplicationContext容器时触发该事件。
3. ContextStopedEvent: 
   当使用ConfigurableApplicationContext接口的stop()方法停止ApplicationContext容器时触发该事件。