springboot项目启动成功后执行一段代码的两种方式

旧城等待， 2022-10-14 12:56 208阅读 0赞

实现ApplicationRunner接口
    复制代码
    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();
        }
    }
    复制代码
     
    
    项目启动后，会打印如下信息：
    
    
    
     
    
     
    
    实现CommandLineRunner接口
    复制代码
    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();
        }
    }
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     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： 
    
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    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);
            }
        }
    }
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     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