什么？Spring Boot CommandLineRunner 有坑！？
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作者 | 狮子头儿文章源自JAVA秀-https://www.javaxiu.com/27618.html
来源 | https://blog.csdn.net/zwq_zwq_zwq/article/details/81059017文章源自JAVA秀-https://www.javaxiu.com/27618.html
使用场景
在应用程序开发过程中，往往我们需要在容器启动的时候执行一些操作。文章源自JAVA秀-https://www.javaxiu.com/27618.html
Spring Boot中提供了CommandLineRunner和ApplicationRunner两个接口来实现这样的需求。文章源自JAVA秀-https://www.javaxiu.com/27618.html
两个接口的不同
参数不同，其他大体相同，可根据实际需求选择合适的接口使用。文章源自JAVA秀-https://www.javaxiu.com/27618.html
CommandLineRunner接口中run方法的参数为String数组，ApplicationRunner中run方法的参数为ApplicationArguments。文章源自JAVA秀-https://www.javaxiu.com/27618.html
特殊的场景
在启动项目时，有时候我们所做的操作可能不是一次性的操作，有可能循环查询数据库，根据结果来处理不同的业务，亦或是监听消息队列……文章源自JAVA秀-https://www.javaxiu.com/27618.html
遇到的坑
看下面一个例子，我们启动一个spring boot项目，正常启动情况下，项目启动后会打印启动时间。文章源自JAVA秀-https://www.javaxiu.com/27618.html
如下图所示：文章源自JAVA秀-https://www.javaxiu.com/27618.html
2018-07-16 01:48:22.378 INFO 9164 --- [ main] o.s.j.e.a.AnnotationMBeanExporter : Registering beans for JMX exposure on startup2018-07-16 01:48:22.386 INFO 9164 --- [ main] o.s.c.support.DefaultLifecycleProcessor : Starting beans in phase 21474836472018-07-16 01:48:22.386 INFO 9164 --- [ main] d.s.w.p.DocumentationPluginsBootstrapper : Context refreshed2018-07-16 01:48:22.396 INFO 9164 --- [ main] d.s.w.p.DocumentationPluginsBootstrapper : Found 1 custom documentation plugin(s)2018-07-16 01:48:22.417 INFO 9164 --- [ main] s.d.s.w.s.ApiListingReferenceScanner : Scanning for api listing references2018-07-16 01:48:22.546 INFO 9164 --- [ main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8088 (http)2018-07-16 01:48:22.555 INFO 9164 --- [ main] com.hello.word.WordParseApplication : Started WordParseApplication in 3.811 seconds (JVM running for 4.486)下面我们模拟一下启动项目时使用CommandLineRunner，有人说CommandLineRunner是项目启动完成后才调用的，我们看看现象。文章源自JAVA秀-https://www.javaxiu.com/27618.html
@Componentpublic class RunService implements CommandLineRunner { public void run(String... strings){ int i =0; while(true){ i++; try { Thread.sleep(10000); System.out.println("过去了10秒钟……,i的值为："+i); } catch (InterruptedException e) { e.printStackTrace(); } if(i==4){ //第40秒时抛出一个异常 throw new RuntimeException(); } continue; } }}再次启动spring boot 项目，看看日志，直接报错，启动异常了。文章源自JAVA秀-https://www.javaxiu.com/27618.html
2018-07-16 01:56:43.703 INFO 7424 --- [ main] o.s.c.support.DefaultLifecycleProcessor : Starting beans in phase 21474836472018-07-16 01:56:43.703 INFO 7424 --- [ main] d.s.w.p.DocumentationPluginsBootstrapper : Context refreshed2018-07-16 01:56:43.722 INFO 7424 --- [ main] d.s.w.p.DocumentationPluginsBootstrapper : Found 1 custom documentation plugin(s)2018-07-16 01:56:43.750 INFO 7424 --- [ main] s.d.s.w.s.ApiListingReferenceScanner : Scanning for api listing references2018-07-16 01:56:43.885 INFO 7424 --- [ main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8088 (http)过去了10秒钟……,i的值为：1过去了10秒钟……,i的值为：2过去了10秒钟……,i的值为：3过去了10秒钟……,i的值为：42018-07-16 01:57:23.939 INFO 7424 --- [ main] utoConfigurationReportLoggingInitializer : Error starting ApplicationContext. To display the auto-configuration report re-run your application with 'debug' enabled.2018-07-16 01:57:23.973 ERROR 7424 --- [ main] o.s.boot.SpringApplication : Application startup failed java.lang.IllegalStateException: Failed to execute CommandLineRunner at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:735) [spring-boot-1.5.9.RELEASE.jar:1.5.9.RELEASE] at org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:716) [spring-boot-1.5.9.RELEASE.jar:1.5.9.RELEASE] at org.springframework.boot.SpringApplication.afterRefresh(SpringApplication.java:703) [spring-boot-1.5.9.RELEASE.jar:1.5.9.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:304) [spring-boot-1.5.9.RELEASE.jar:1.5.9.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:1118) [spring-boot-1.5.9.RELEASE.jar:1.5.9.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:1107) [spring-boot-1.5.9.RELEASE.jar:1.5.9.RELEASE] at com.hello.word.WordParseApplication.main(WordParseApplication.java:15) [classes/:na]Caused by: java.lang.RuntimeException: null at com.zhangwq.service.RunService.run(RunService.java:24) ~[classes/:na] at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:732) [spring-boot-1.5.9.RELEASE.jar:1.5.9.RELEASE] ... 6 common frames omitted 2018-07-16 01:57:23.975 INFO 7424 --- [ main] ationConfigEmbeddedWebApplicationContext : Closing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@14a4e18: startup date [Mon Jul 16 01:56:39 CST 2018]; root of context hierarchy2018-07-16 01:57:23.975 INFO 7424 --- [ main] o.s.c.support.DefaultLifecycleProcessor : Stopping beans in phase 21474836472018-07-16 01:57:23.975 INFO 7424 --- [ main] o.s.j.e.a.AnnotationMBeanExporter : Unregistering JMX-exposed beans on shutdown Process finished with exit code 1说明启动CommandLineRunner的执行其实是整个应用启动的一部分，没有打印最后的启动时间，说明项目是在CommandLineRunner执行完成之后才启动完成的。文章源自JAVA秀-https://www.javaxiu.com/27618.html
此时CommandLineRunner的run方法执行的是一个循环，循环到第四次的时候，抛出异常，直接影响主程序的启动。文章源自JAVA秀-https://www.javaxiu.com/27618.html
填坑
这样的问题该如何解决呢？文章源自JAVA秀-https://www.javaxiu.com/27618.html
这个操作影响了主线程，那么我们是否可以重新开启一个线程，让他单独去做我们想要做的操作呢。文章源自JAVA秀-https://www.javaxiu.com/27618.html
@Componentpublic class RunService implements CommandLineRunner { public void run(String... strings){ new Thread(){ public void run() { int i = 0; while (true) { i++; try { Thread.sleep(10000); System.out.println("过去了10秒钟……,i的值为：" + i); } catch (InterruptedException e) { e.printStackTrace(); } if (i == 4) { //第40秒时抛出一个异常 throw new RuntimeException(); } continue; } } }.start(); }}我们再看看这次的日志是什么样的：文章源自JAVA秀-https://www.javaxiu.com/27618.html
2018-07-16 02:05:52.680 INFO 7148 --- [ main] o.s.c.support.DefaultLifecycleProcessor : Starting beans in phase 21474836472018-07-16 02:05:52.680 INFO 7148 --- [ main] d.s.w.p.DocumentationPluginsBootstrapper : Context refreshed2018-07-16 02:05:52.695 INFO 7148 --- [ main] d.s.w.p.DocumentationPluginsBootstrapper : Found 1 custom documentation plugin(s)2018-07-16 02:05:52.717 INFO 7148 --- [ main] s.d.s.w.s.ApiListingReferenceScanner : Scanning for api listing references2018-07-16 02:05:52.815 INFO 7148 --- [ main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8088 (http)2018-07-16 02:05:52.819 INFO 7148 --- [ main] com.hello.word.WordParseApplication : Started WordParseApplication in 3.406 seconds (JVM running for 4.063)过去了10秒钟……,i的值为：1过去了10秒钟……,i的值为：2过去了10秒钟……,i的值为：3过去了10秒钟……,i的值为：4Exception in thread "Thread-10" java.lang.RuntimeException at com.zhangwq.service.RunService$1.run(RunService.java:26)此时CommandLineRunner执行的操作和主线程是相互独立的，抛出异常并不会影响到主线程。文章源自JAVA秀-https://www.javaxiu.com/27618.html
程序打印了启动时间，并且CommandLineRunner中run方法报错后，应用程序并没有因为异常而终止。填坑成功。文章源自JAVA秀-https://www.javaxiu.com/27618.html
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