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