Plugin ‘org.apache.tomcat.maven:tomcat7-maven-plugin:‘ not found

   <build>
        <plugins>
            <plugin>
                <groupId>org.apache.tomcat.maven</groupId>
                <artifactId>tomcat7-maven-plugin</artifactId>
                <version>2.2</version>
                <configuration>
                    <!-- 指定端口 -->
                    <port>81</port>
                    <!-- 请求路径 -->
                    <path>/</path>
                </configuration>
            </plugin>
        </plugins>
    </build>

Add the version field to the original configuration. And the version number is set to the latest version 2.2 of the central warehouse