IDEA上面搭建一个SpringBoot的web-mvc项目遇到的问题

<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"      xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">   <modelVersion>4.0.0</modelVersion>   <groupId>com.example</groupId>   <artifactId>demo</artifactId>   <version>0.0.1-SNAPSHOT</version>   <packagingexample>jar</packagingexample>   <name>demo</name>   <description>Demo project for Spring Boot</description>   <parent>     <groupId>org.springframework.boot</groupId>     <artifactId>spring-boot-starter-parent</artifactId>     <version>1.4.0.RELEASE</version>     <relativePath/> <!-- lookup parent from repository -->   </parent>   <properties>     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>     <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>     <java.version>1.8</java.version>   </properties>   <dependencies>     <dependency>       <groupId>org.springframework.boot</groupId>       <artifactId>spring-boot-starter-web</artifactId>     </dependency>     <dependency>       <groupId>org.springframework.boot</groupId>       <artifactId>spring-boot-starter-test</artifactId>       <scope>test</scope>     </dependency>     <dependency>       <groupId>org.springframework.boot</groupId>       <artifactId>spring-boot-starter-thymeleaf</artifactId>     </dependency>   </dependencies>   <build>     <plugins>       <plugin>         <groupId>org.springframework.boot</groupId>         <artifactId>spring-boot-maven-plugin</artifactId>       </plugin>     </plugins>   </build> </project>