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