title: Intellij Springboot problems on startup
body: <p>I am really new with spring boot, so I started with some tutorials to create a simple Rest example (my final goal is to integrate it with mongodb, but I need to start!). 
  I created a new project on IntelliJ with Spring Initializr and choosed Web and Mongodb as features. 
  Then I added only a class, </p>
  
  <pre><code>import org.springframework.web.bind.annotation.RequestMapping;
  import org.springframework.web.bind.annotation.RestController;
  
  @RestController
  public class HelloController {
  
  @RequestMapping("/")
  public String index() {
      return "Greetings from Spring Boot!";
  }
  
  }
  </code></pre>
  
  <p>When I run the project, the console is </p>
  
  <pre><code> 2018-09-03 20:08:33.139  INFO 1363 --- [           main] 
   test.test.TestApplication                : Starting TestApplication on 
   MacBook-Pro-di-Stefano.local with PID 1363 
   (/Users/stefanomiceli/IdeaProjects/test/target/classes started by 
   stefanomiceli in /Users/stefanomiceli/IdeaProjects/test)
   2018-09-03 20:08:33.141  INFO 1363 --- [           main] 
   test.test.TestApplication                : No active profile set, 
   falling back to default profiles: default
   2018-09-03 20:08:33.173  INFO 1363 --- [           main] 
   ConfigServletWebServerApplicationContext : Refreshing 
  
  org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@15713d56: startup date [Mon Sep 03 20:08:33 PDT 2018]; root of context hierarchy
  
   WARNING: An illegal reflective access operation has occurred
   WARNING: Illegal reflective access by 
   org.springframework.cglib.core.ReflectUtils$1 
   (file:/Users/stefanomiceli/.m2/repository/org/springframework/spring- 
   core/5.0.8.RELEASE/spring-core-5.0.8.RELEASE.jar) to method 
  
  
  java.lang.ClassLoader.defineClass(java.lang.String,byte[],int,int,java.security.ProtectionDomain)
  
   WARNING: Please consider reporting this to the maintainers of 
   org.springframework.cglib.core.ReflectUtils$1
   WARNING: Use --illegal-access=warn to enable warnings of further 
   illegal reflective access operations
   WARNING: All illegal access operations will be denied in a future 
   release
   2018-09-03 20:08:33.950  INFO 1363 --- [           main] 
   o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with 
   port(s): 8080 (http)
   2018-09-03 20:08:33.969  INFO 1363 --- [           main] 
   o.apache.catalina.core.StandardService   : Starting service [Tomcat]
   2018-09-03 20:08:33.969  INFO 1363 --- [           main] 
   org.apache.catalina.core.StandardEngine  : Starting Servlet Engine: 
   Apache Tomcat/8.5.32
   2018-09-03 20:08:33.972  INFO 1363 --- [ost-startStop-1] 
   o.a.catalina.core.AprLifecycleListener   : The APR based Apache Tomcat 
   Native library which allows optimal performance in production 
   environments was not found on the java.library.path: 
  
  
   [/Users/stefanomiceli/Library/Java/Extensions:/Library/Java/Extensions:/Network/Library/Java/Extensions:/System/Library/Java/Extensions:/usr/lib/java:.]
  
   2018-09-03 20:08:34.021  INFO 1363 --- [ost-startStop-1] o.a.c.c.C. 
   [Tomcat].[localhost].[/]       : Initializing Spring embedded 
   WebApplicationContext
   2018-09-03 20:08:34.021  INFO 1363 --- [ost-startStop-1] 
   o.s.web.context.ContextLoader            : Root WebApplicationContext: 
   initialization completed in 852 ms
   2018-09-03 20:08:34.059  INFO 1363 --- [ost-startStop-1] 
   o.s.b.w.servlet.ServletRegistrationBean  : Servlet dispatcherServlet 
   mapped to [/]
   2018-09-03 20:08:34.061  INFO 1363 --- [ost-startStop-1] 
   o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 
   'characterEncodingFilter' to: [/*]
   2018-09-03 20:08:34.062  INFO 1363 --- [ost-startStop-1] 
   o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 
   'hiddenHttpMethodFilter' to: [/*]
   2018-09-03 20:08:34.062  INFO 1363 --- [ost-startStop-1] 
   o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 
   'httpPutFormContentFilter' to: [/*]
   2018-09-03 20:08:34.062  INFO 1363 --- [ost-startStop-1] 
   o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 
   'requestContextFilter' to: [/*]
   2018-09-03 20:08:34.143  INFO 1363 --- [           main] 
   o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path 
   [/**/favicon.ico] onto handler of type [class 
   org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
   2018-09-03 20:08:34.310  INFO 1363 --- [           main] 
   s.w.s.m.m.a.RequestMappingHandlerAdapter : Looking for 
   @ControllerAdvice: 
  
  
  
  org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@15713d56: startup date [Mon Sep 03 20:08:33 PDT 2018]; root of context hierarchy
  
   2018-09-03 20:08:34.344  INFO 1363 --- [           main] 
   s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error]}" onto 
   public 
      org.springframework.http.ResponseEntity&lt;java.util.Map&lt;java.lang.String, java.lang.Object&gt;&gt; 
    org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController.error(javax.servlet.http.HttpServletRequest)
  
   2018-09-03 20:08:34.345  INFO 1363 --- [           main] 
   s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error],produces=      [text/html]}" onto public org.springframework.web.servlet.ModelAndView 
  
  
  org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController.errorHtml(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse)
  
   2018-09-03 20:08:34.362  INFO 1363 --- [           main] 
   o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path 
   [/webjars/**] onto handler of type [class 
   org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
   2018-09-03 20:08:34.362  INFO 1363 --- [           main] 
   o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**] onto 
   handler of type [class 
   org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
   2018-09-03 20:08:34.550  INFO 1363 --- [           main] 
   org.mongodb.driver.cluster               : Cluster created with 
   settings {hosts=[localhost:27017], mode=SINGLE, 
   requiredClusterType=UNKNOWN, serverSelectionTimeout='30000 ms', 
   maxWaitQueueSize=500}
   2018-09-03 20:08:34.582  INFO 1363 --- [localhost:27017] 
   org.mongodb.driver.connection            : Opened connection 
   [connectionId{localValue:1, serverValue:55}] to localhost:27017
   2018-09-03 20:08:34.585  INFO 1363 --- [localhost:27017] 
   org.mongodb.driver.cluster               : Monitor thread successfully 
   connected to server with description 
   ServerDescription{address=localhost:27017, type=STANDALONE, 
   state=CONNECTED, ok=true, version=ServerVersion{versionList=[4, 0, 
   1]}, minWireVersion=0, maxWireVersion=7, maxDocumentSize=16777216, 
   logicalSessionTimeoutMinutes=30, roundTripTimeNanos=1582641}
   2018-09-03 20:08:34.739  INFO 1363 --- [           main] 
   o.s.j.e.a.AnnotationMBeanExporter        : Registering beans for JMX 
   exposure on startup
   2018-09-03 20:08:34.768  INFO 1363 --- [           main] 
   o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 
   8080 (http) with context path ''
   2018-09-03 20:08:34.772  INFO 1363 --- [           main] 
   test.test.TestApplication                : Started TestApplication in 
   1.834 seconds (JVM running for 7.413)
  </code></pre>
  
  <p>But when I go on <code>localhost:8080/</code> I get <code>404</code> error. What did I do wrong in my <em>helloworld</em>? Is there anything that should I make before running the application? </p>