spring-boot 错误 This application has no explicit mapping for /error, so you are s

<dependency>

      <groupId>org.apache.tomcat.embed</groupId>

      <artifactId>tomcat-embed-jasper</artifactId>

      <scope>provided</scope>

    </dependency>



    <dependency>

      <groupId>javax.servlet</groupId>

      <artifactId>javax.servlet-api</artifactId>

      <!--   <scope>provided</scope> -->

    </dependency>



    <dependency>

      <groupId>javax.servlet</groupId>

      <artifactId>jstl</artifactId>

    </dependency>

@Controller

public class Sign {



    @RequestMapping("/")

    public String index(){

        System.out.println("HELLO world");

        return "index";

    }

}