Spring boot CommandLineRunner接口使用例子

前言

Spring boot的CommandLineRunner接口主要用于实现在应用初始化后,去执行一段代码块逻辑,这段初始化代码在整个应用生命周期内只会执行一次。

如何使用CommandLineRunner接口

我们可以用以下三种方式去使用CommandLineRunner接口:

1)和@Component注解一起使用

这种使用方式相当简便,如下所示:

@Component
public class ApplicationStartupRunner implements CommandLineRunner {
    protected final Log logger = LogFactory.getLog(getClass());
 
    @Override
    public void run(String... args) throws Exception {
        logger.info("ApplicationStartupRunner run method Started !!");
    }
}

2)和@SpringBootApplication注解一起使用

这种使用方式也相当的简单,参考代码如下:

@SpringBootApplication
public class SpringBootWebApplication extends SpringBootServletInitializer implements CommandLineRunner {
 
    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
        return application.sources(SpringBootWebApplication.class);
    }
 
    public static void main(String[] args) throws Exception {
        SpringApplication.run(SpringBootWebApplication.class, args);
    }
 
 
    @Override
    public void run(String... args) throws Exception {
        logger.info("Application Started !!");
    }
}

3)声明一个实现了CommandLineRunner接口的Bean

这种方式其实也大同小异,就是在SpringBootApplication里定义一个Bean,改Bean实现了CommandLineRunner接口,参考代码如下:

ApplicationStartupRunner.java

public class ApplicationStartupRunner implements CommandLineRunner {
    protected final Log logger = LogFactory.getLog(getClass());
    @Override
    public void run(String... args) throws Exception {
        logger.info("Application Started !!");
    }
}

注册ApplicationStartupRunner bean

@SpringBootApplication
public class SpringBootWebApplication extends SpringBootServletInitializer {
 
    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
        return application.sources(SpringBootWebApplication.class);
    }
 
    public static void main(String[] args) throws Exception {
        SpringApplication.run(SpringBootWebApplication.class, args);
    }
 
    @Bean
    public ApplicationStartupRunner schedulerRunner() {
        return new ApplicationStartupRunner();
    }
}

注意:在实现CommandLineRunner接口时,run(String… args)方法内部如果抛异常的话,会直接导致应用启动失败,所以,一定要记得将危险的代码放在try-catch代码块里。

用@Order注解去设置多个CommandLineRunner实现类的执行顺序

一个应用可能存在多个 CommandLineRunner接口实现类,如果我们想设置它们的执行顺序,可以使用 @Order实现

@Order(value=3)
@Component
class ApplicationStartupRunnerOne implements CommandLineRunner {
    protected final Log logger = LogFactory.getLog(getClass());
 
    @Override
    public void run(String... args) throws Exception {
        logger.info("ApplicationStartupRunnerOne run method Started !!");
    }
}
 
@Order(value=2)
@Component
class ApplicationStartupRunnerTwo implements CommandLineRunner {
    protected final Log logger = LogFactory.getLog(getClass());
 
    @Override
    public void run(String... args) throws Exception {
        logger.info("ApplicationStartupRunnerTwo run method Started !!");
    }
}

输出日志:

2017-03-08 13:55:04 - ApplicationStartupRunnerTwo run method Started !!
2017-03-08 13:55:04 - ApplicationStartupRunnerOne run method Started !!

为什么要使用CommandLineRunner接口

  • 实现在应用启动后,去执行相关代码逻辑,且只会执行一次;
  • spring batch批量处理框架依赖这些执行器去触发执行任务;
  • 我们可以在run()方法里使用任何依赖,因为它们已经初始化好了;

原文文链

Site4J

posted @ 2018-09-24 19:30  风一样的码农  阅读(13800)  评论(0编辑  收藏