springboot项目启动成功后执行一段代码的两种方式

springboot项目启动成功后执行一段代码的两种方式

实现ApplicationRunner接口

package com.lnjecit.lifecycle;

import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.ApplicationRunner;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

/**
 * @author lnj
 * createTime 2018-11-07 22:37
 **/
@Component
public class ApplicationRunnerImpl implements ApplicationRunner {
    @Override
    public void run(ApplicationArguments args) throws Exception {
        System.out.println("通过实现ApplicationRunner接口，在spring boot项目启动后打印参数");
        String[] sourceArgs = args.getSourceArgs();
        for (String arg : sourceArgs) {
            System.out.print(arg + " ");
        }
        System.out.println();
    }
}

项目启动后，会打印如下信息：

实现CommandLineRunner接口

package com.lnjecit.lifecycle;

import org.springframework.boot.CommandLineRunner;
import org.springframework.stereotype.Component;

/**
 * @author lnj
 * createTime 2018-11-07 22:25
 **/
@Component
public class CommandLineRunnerImpl implements CommandLineRunner {
    @Override
    public void run(String... args) throws Exception {
        System.out.println("通过实现CommandLineRunner接口，在spring boot项目启动后打印参数");
        for (String arg : args) {
            System.out.print(arg + " ");
        }
        System.out.println();
    }
}

两种实现方式的不同之处在于run方法中接收的参数类型不一样

指定执行顺序

当项目中同时实现了ApplicationRunner和CommondLineRunner接口时，可使用Order注解或实现Ordered接口来指定执行顺序，值越小越先执行

原理

通过调试可以发现都是在 org.springframework.boot.SpringApplication#run(java.lang.String...)方法内的afterRefresh（上下文刷新后处理）方法时，会执行callRunners方法。

afterRefresh方法具体实现如下：

protected void afterRefresh(ConfigurableApplicationContext context,
        ApplicationArguments args) {
    callRunners(context, args);
}

callRunners方法具体实现如下：

private void callRunners(ApplicationContext context, ApplicationArguments args) {
    List<Object> runners = new ArrayList<Object>();
    runners.addAll(context.getBeansOfType(ApplicationRunner.class).values());
    runners.addAll(context.getBeansOfType(CommandLineRunner.class).values());
    AnnotationAwareOrderComparator.sort(runners);
    for (Object runner : new LinkedHashSet<Object>(runners)) {
        if (runner instanceof ApplicationRunner) {
            callRunner((ApplicationRunner) runner, args);
        }
        if (runner instanceof CommandLineRunner) {
            callRunner((CommandLineRunner) runner, args);
        }
    }
}

可以看出上下文完成刷新后，依次调用注册的runners, runners的类型为 ApplicationRunner 或 CommandLineRunner

案例地址

https://github.com/linj6/springboot-learn/tree/master/springboot-runner

参考资料

https://blog.csdn.net/zknxx/article/details/52196427