Maven unable to resolve dependencies for Spring Boot and JUnit

I'm trying to learn Spring Boot hands-on and importing the boilerplate for basic spring boot application through Spring Starter using my IntelliJ IDE, but Maven is unable to resolve all dependencies and my project is missing out on important dependencies. I can't figure out the reason for this.

First I thought the problem was using JDK8 for newer versions of the SpringFramework, then I installed JDK11 but the same problem persists and as far as I can understand POM.xml has all the dependencies listed in it.

Screenshot of IDE to get an idea

    <?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.6.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.selfspring</groupId>
    <artifactId>conference-demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>conference-demo</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>11</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>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

    </project>```

here is all the dependencies it is unable to resolve:

Cannot resolve org.hibernate.validator:hibernate-validator:6.0.18.Final
Cannot resolve org.hamcrest:hamcrest:2.1
Cannot resolve org.ow2.asm:asm:5.0.4
Cannot resolve org.springframework:spring-expression:5.2.5.RELEASE
Cannot resolve org.junit.platform:junit-platform-engine:1.5.2
Cannot resolve net.minidev:accessors-smart:1.2
Cannot resolve net.bytebuddy:byte-buddy:1.10.8
Cannot resolve jakarta.xml.bind:jakarta.xml.bind-api:2.3.3
Cannot resolve org.springframework:spring-aop:5.2.5.RELEASE
Cannot resolve com.fasterxml:classmate:1.5.1
Cannot resolve org.junit.jupiter:junit-jupiter-api:5.5.2
Cannot resolve org.mockito:mockito-junit-jupiter:3.1.0
Cannot resolve org.opentest4j:opentest4j:1.2.0
Cannot resolve org.objenesis:objenesis:2.6
Cannot resolve org.springframework:spring-webmvc:5.2.5.RELEASE
Cannot resolve org.springframework.boot:spring-boot-test-autoconfigure:2.2.6.RELEASE
Cannot resolve net.bytebuddy:byte-buddy-agent:1.10.8
Cannot resolve org.junit.jupiter:junit-jupiter:5.5.2
Cannot resolve org.springframework.boot:spring-boot-test:2.2.6.RELEASE
Cannot resolve jakarta.validation:jakarta.validation-api:2.0.2
Cannot resolve org.jboss.logging:jboss-logging:3.4.1.Final
Cannot resolve net.minidev:json-smart:2.3
Cannot resolve org.springframework:spring-test:5.2.5.RELEASE
Cannot resolve org.assertj:assertj-core:3.13.2
Cannot resolve jakarta.activation:jakarta.activation-api:1.2.2
Cannot resolve org.skyscreamer:jsonassert:1.5.0
Cannot resolve org.springframework.boot:spring-boot-starter-test:2.2.6.RELEASE
Cannot resolve org.mockito:mockito-core:3.1.0
Cannot resolve com.vaadin.external.google:android-json:0.0.20131108.vaadin1
Cannot resolve com.jayway.jsonpath:json-path:2.4.0
Cannot resolve org.junit.jupiter:junit-jupiter-params:5.5.2
Cannot resolve org.xmlunit:xmlunit-core:2.6.4
Cannot resolve org.springframework:spring-jcl:5.2.5.RELEASE
Cannot resolve org.apiguardian:apiguardian-api:1.1.0
Cannot resolve org.springframework:spring-beans:5.2.5.RELEASE
Cannot resolve org.junit.jupiter:junit-jupiter-engine:5.5.2
Cannot resolve org.junit.platform:junit-platform-commons:1.5.2


</details>


# 答案1
**得分**: 5

尝试删除你的 .m2 文件夹，然后再次拉取依赖。我通常是这样做的：
从 .m/repo 中删除所有内容，然后我进入 IntelliJ，在 pom.xml 中加入空格并删除它，这样它会提示我拉取在 pom.xml 中进行的更改。

编辑：
如果这没有帮助，你始终可以运行以下命令：

    mvn clean - 清除依赖，使你获得类似于全新状态的干净环境

    mvn install - 初始化重新拉取依赖

<details>
<summary>英文:</summary>

Try nuking your .m2 folder, and then pull dependencies again. I usually do it like this:
delete everything from .m/repo, I go to intellij and add space in pom.xml and delete it so it offers me to pull changes that were made in pom.xml

EDIT:
If that does not help, you can always run

    mvn clean - clear dependencies so you get something like a clean slate

    mvn install - initiates the pulling of dependencies again

</details>