春季：java.lang.ClassNotFoundException：找不到org.springframework.boot.SpringApplication

这是我的pom.xml文件：

<?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>SpringBootGame</groupId>
    <artifactId>SpringBootGame</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <version>2.0.3.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot</artifactId>
            <version>2.0.3.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.json</groupId>
            <artifactId>json</artifactId>
            <version>20090211</version>
        </dependency>

    </dependencies>

    <properties>
        <java.version>1.8</java.version>
    </properties>


    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <version>2.0.3.RELEASE</version>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-jar-plugin</artifactId>
                <version>3.0.2</version>
                <configuration>
                    <archive>
                        <manifest>
                            <mainClass>com.game.Main</mainClass>
                        </manifest>
                    </archive>
                </configuration>
            </plugin>
        </plugins>

    </build>

</project>

我通过“ mvn clean install”构建我的jar文件，然后运行“ java -jar target \ SpringBootGame-1.0-SNAPSHOT.jar”提取的jar文件。

然后，我得到一个错误：

线程“主”中的异常java.lang.NoClassDefFoundError：org / springframework / boot / SpringApplication在com.game.Main.main（Main.java:15）由以下原因引起：java.lang.ClassNotFoundException：org.springframework.boot.SpringApplication在java.net.URLClassLoader.findClass（未知源）在java.lang.ClassLoader.loadClass（未知源）在sun.misc.Launcher $ AppClassLoader.loadClass（未知源）在java.lang.ClassLoader.loadClass（未知源） ...还有1个

你知道是什么问题吗？