SpringBoot基础启动加载器

实现CommandLineRunner 接口

&＃64;Order(1)
&＃64;Component
public class FirstCommandlineRunner implements CommandLineRunner {&＃64;Overridepublic void run(String... args) throws Exception {System.out.println("&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;FirstCommandlineRunner&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;");}
}


实现ApplicationRunner 接口

&＃64;Order(1)
&＃64;Component
public class SecondApplicationRunner implements ApplicationRunner {&＃64;Overridepublic void run(ApplicationArguments args) throws Exception {System.out.println("&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;SecondApplicationRunner&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;");}
}


两种实现方式比较

相同点

• 调用点一样
  都是在callRunners中调用

• 实现方法名一样
  都是通过实现接口来重写run方法

• 通过Order来决定实现顺序

差异点

• 执行优先级差异&＃xff0c;第二种 > 第一种
• run方法入参不一致
  CommandLineRunner 实现run传入String… args
  ApplicationRunner 实现run传入ApplicationArguments args

执行结果

有执行结果可以看出&＃xff0c;两种实现方式的Order一样&＃xff0c;但是第二种的执行顺序早于第一种执行顺序&＃xff0c;为什么会是这样的执行顺序&＃xff0c;继续往下看

run()方法中调用&＃xff1a;callRunners

private void callRunners(ApplicationContext context, ApplicationArguments args) {List<Object> runners &＃61; new ArrayList<>();runners.addAll(context.getBeansOfType(ApplicationRunner.class).values());runners.addAll(context.getBeansOfType(CommandLineRunner.class).values());AnnotationAwareOrderComparator.sort(runners);for (Object runner : new LinkedHashSet<>(runners)) {if (runner instanceof ApplicationRunner) {callRunner((ApplicationRunner) runner, args);}if (runner instanceof CommandLineRunner) {callRunner((CommandLineRunner) runner, args);}}
}


• 在方法中首先获得ApplicationRunner和CommandLineRunner接口的实现类&＃xff0c;然后对runners进行排序&＃xff0c;排序后遍历调用执行callRunner方法
• List runners &＃61; new ArrayList<>(); 用的是object来装所有的Runner&＃xff0c;在排序的时候对两种实现都采用Order注解排序&＃xff0c;所以会对两种实现方式基于Order来排序
• 上面的两种实现方式&＃xff0c;由于Order值一样都是1&＃xff0c;但是runners.addAll()是添加ApplicationRunner接口实现对象&＃xff0c;runners是个有序集合&＃xff0c;所以第二种的执行顺序早于第一种

private void callRunner(ApplicationRunner runner, ApplicationArguments args) {try {(runner).run(args);}catch (Exception ex) {throw new IllegalStateException("Failed to execute ApplicationRunner", ex);}
}private void callRunner(CommandLineRunner runner, ApplicationArguments args) {try {(runner).run(args.getSourceArgs());}catch (Exception ex) {throw new IllegalStateException("Failed to execute CommandLineRunner", ex);}
}