Spring project error using thymeleaf, Compilation failure. How can I fix this? - spring

Question

I'm pretty new at Spring framework, and I try to start a project for practice.
But I have an error and I have no idea how to fix this.
I've created a new Spring project in IntelliJ Idea, with Spring Initializr option (In Intellij, not with start.spring.io ). I added only 2 dependedncies for start (Web and Thymeleaf), but it throws error for Thymeleaf dependency if i run it with
'mvn spring-boot:run' command.
My spring project is "empty" , I have no controllers, beans, jpa entites, etc.. but it i think it shound run in this way too. I just wanted to make sure if it works if I run it.
If I create a same project, without Thymeleaf dependency (only Web dependency), it starts correctly on localhost.
I'm using Java 9.0.4 and Apache Maven 3.5.3
My error log
pom.xml:
<?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_thymeleaf</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>demo_thymeleaf</name>
<description>Demo project for Spring Boot</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.0.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>9</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>
<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>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>

Answer 1

I solved it with deleting the whole C\Users\user.m2 directory.
After then with 'mvn spring-boot:run' it started successfully on localhost.
But I've got one more question:
When I run it, at terminal there are a couple of Warning messages.
Spring application runs anyway, but is there something to do with these messages?
Warning messages during Spring application run.