• 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

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  • 原文地址:https://www.cnblogs.com/zuidongfeng/p/9926471.html
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