如何使用Spring(Tomcat服务器)和Maven创建Web应用程序

Question

运行应用程序时，我会收到下面的控制台消息，但每次导航到http://localhost:8080/?我收到一条错误消息，上面写着：

"白标签错误页此应用程序没有/error的显式映射，因此您将其视为回退。

2021年1月12日星期二美国东部时间22:04:40出现意外错误(类型=未找到，状态=404("；

控制台输出：

2021-01-12 22:03:17.212  INFO 21710 --- [           main] com.crd.carrental.CarRentalApplication   : No active profile set, falling back to default profiles: default
2021-01-12 22:03:18.343  INFO 21710 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2021-01-12 22:03:18.350  INFO 21710 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2021-01-12 22:03:18.350  INFO 21710 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.39]
2021-01-12 22:03:18.424  INFO 21710 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2021-01-12 22:03:18.424  INFO 21710 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 1073 ms
2021-01-12 22:03:18.539  INFO 21710 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'clientInboundChannelExecutor'
2021-01-12 22:03:18.542  INFO 21710 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'clientOutboundChannelExecutor'
2021-01-12 22:03:18.548  INFO 21710 --- [           main] o.s.s.c.ThreadPoolTaskScheduler          : Initializing ExecutorService 'messageBrokerTaskScheduler'
2021-01-12 22:03:18.613  INFO 21710 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'brokerChannelExecutor'
2021-01-12 22:03:19.539  INFO 21710 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2021-01-12 22:03:19.541  INFO 21710 --- [           main] o.s.m.s.b.SimpleBrokerMessageHandler     : Starting...
2021-01-12 22:03:19.541  INFO 21710 --- [           main] o.s.m.s.b.SimpleBrokerMessageHandler     : BrokerAvailabilityEvent[available=true, SimpleBrokerMessageHandler [DefaultSubscriptionRegistry[cache[0 destination(s)], registry[0 sessions]]]]
2021-01-12 22:03:19.541  INFO 21710 --- [           main] o.s.m.s.b.SimpleBrokerMessageHandler     : Started.
2021-01-12 22:03:19.551  INFO 21710 --- [           main] com.crd.carrental.CarRentalApplication   : Started CarRentalApplication in 2.977 seconds (JVM running for 5.797)
2021-01-12 22:04:18.616  INFO 21710 --- [MessageBroker-1] o.s.w.s.c.WebSocketMessageBrokerStats    : WebSocketSession[0 current WS(0)-HttpStream(0)-HttpPoll(0), 0 total, 0 closed abnormally (0 connect failure, 0 send limit, 0 transport error)], stompSubProtocol[processed CONNECT(0)-CONNECTED(0)-DISCONNECT(0)], stompBrokerRelay[null], inboundChannel[pool size = 0, active threads = 0, queued tasks = 0, completed tasks = 0], outboundChannel[pool size = 0, active threads = 0, queued tasks = 0, completed tasks = 0], sockJsScheduler[pool size = 1, active threads = 1, queued tasks = 0, completed tasks = 0]
2021-01-12 22:04:23.920  INFO 21710 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring DispatcherServlet 'dispatcherServlet'
2021-01-12 22:04:23.920  INFO 21710 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Initializing Servlet 'dispatcherServlet'
2021-01-12 22:04:23.929  INFO 21710 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Completed initialization in 9 ms```

Answer 1

确保已为请求的url"/"定义了Controller，如下所示：

@RequestMapping("/")
public String homePage() {
... <your code>
return "home";
}

并且，您的home页面必须存储在以下路径中：

|--resources
|--templates
|--home.html

Answer 2

当您正在搜索的URL没有页面时，就会出现白标签错误。所以在你的控制器中查看是否存在"0"的映射/&"；。

Answer 3

白色错误标签是没有任何控制器路径的空Spring应用程序的预期行为。除非您没有配置任何REST路径或端点，否则会显示此错误。

如果错误仍然存在，请确保您的主应用程序类扩展了SpringBootServletInitializer，并且您正在编写适当的端点路径。