springboot - Runner

ApplicationRunner and CommandLineRunner

开发中可能会遇到这样的需求，需要在容器启动的时候执行一些内容，比如读取配置文件，数据库操作等等。SpringBoot给我们提供了两个接口来帮助我们定制这种需求，这两个接口分别为CommandLineRunner和ApplicationRunner，他们会在容器启动完成后执行。这两个接口中有一个run方法，我们只需要实现这个方法即可。这两个接口的不同之处在于：ApplicationRunner中run方法的参数为ApplicationArguments，而CommandLineRunner接口中run方法的参数为String数组。

public interface ApplicationRunner {
void run(ApplicationArguments var1) throws Exception;
}
public interface CommandLineRunner {
void run(String... var1) throws Exception;
}

1、 在SpringApplication的启动方法run中，完成上下文刷新后，会执行afterRefresh 方法

public ConfigurableApplicationContext run(String... args) {
...
try {
...
this.prepareContext(context, environment, listeners, ex, printedBanner);
this.refreshContext(context);
this.afterRefresh(context, ex);
...
}
return context;
} catch (Throwable var9) {
...
}
}

2、 在afterRefresh方法中，会调用两种Runners，主要就是查找上下文中所有实现了ApplicationRunner 和 CommandLineRunner接口的bean，然后执行其run方法，这样我们就有机会定制自己的代码。

protected void afterRefresh(ConfigurableApplicationContext context, ApplicationArguments args) {
this.callRunners(context, args);
}
private void callRunners(ApplicationContext context, ApplicationArguments args) {
ArrayList runners = new ArrayList();
runners.addAll(context.getBeansOfType(ApplicationRunner.class).values());
runners.addAll(context.getBeansOfType(CommandLineRunner.class).values());
AnnotationAwareOrderComparator.sort(runners);
Iterator var4 = (new LinkedHashSet(runners)).iterator();
while(var4.hasNext()) {
Object runner = var4.next();
if(runner instanceof ApplicationRunner) {
this.callRunner((ApplicationRunner)runner, args);
}
if(runner instanceof CommandLineRunner) {
this.callRunner((CommandLineRunner)runner, args);
}
}
}

3、 分别实现ApplicationRunner 和 CommandLineRunner如下：

public class MyApplicationRunner implements ApplicationRunner {
private final Logger logger = LoggerFactory.getLogger(MyApplicationRunner.class);
@Override
public void run(ApplicationArguments applicationArguments) throws Exception {
logger.info("MyApplicationRunner.run() is invoked! " + applicationArguments);
}
}

public class MyCommandLineRunner implements CommandLineRunner {
private final Logger logger
= LoggerFactory.getLogger(MyCommandLineRunner.class);
@Override
public void run(String... strings) throws Exception {
logger.info("MyCommandLineRunner.run() is invoked! " + strings);
}
}

4、将上述实现的类，配置为bean

@SpringBootApplication
public class Application {
@Bean
public MyCommandLineRunner startupRunner(){
return new MyCommandLineRunner();
}
@Bean
public MyApplicationRunner myApplicationRunner(){
return new MyApplicationRunner();
}
public static void main(String[] args) {
SpringApplication app = new SpringApplication(Application.class);
app.setBannerMode(Banner.Mode.OFF);
app.run(args);
}
}

5、执行main方法，可以看到输出如下内容：

...
2017-08-25 16:31:12.150
INFO 58583 --- [
main] c.s.boot.runner.MyApplicationRunner
: MyApplicationRunner.run() is invoked! org.springframework.boot.DefaultApplicationArguments@70925b45
2017-08-25 16:31:12.150
INFO 58583 --- [
main] c.s.boot.runner.MyCommandLineRunner
: MyCommandLineRunner.run() is invoked! [Ljava.lang.String;@1b9ea3e3
2017-08-25 16:31:12.152
INFO 58583 --- [
main] com.spring.boot.Application
: Started Application in 11.905 seconds (JVM running for 12.237)

最后

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