在spring cloud服务中，有一个ms-code项目，只为所有的微服务提供核心依赖和工具类，没有业务意义，作为核心依赖使用。所以没有main方法，没有启动类。
在spring cloud整体打包的过程中报错：
[INFO] --- maven-jar-plugin:3.0.:jar (default-jar) @ springcloud-ms-core ---
[INFO] Building jar: D:\document\IdeaProjects\springcloud\springcloud-ms-core\target\springcloud-ms-core-0.0.-SNAPSHOT.jar
[INFO]
[INFO] --- spring-boot-maven-plugin:2.0..RELEASE:repackage (default) @ springcloud-ms-core ---
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 3.425 s
[INFO] Finished at: --07T11::+:
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.springframework.boot:spring-boot-maven-plugin:2.0..RELEASE:repackage (default) on project springcloud-ms-core: Execution default of goal org.springframework.boot:spring-boot-maven-plugin:2.0..RELEASE:repackage failed: Unable to find main class -> [Help ]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help ] http://cwiki.apache.org/confluence/display/MAVEN/PluginExecutionException
提示：
错误原因就是没有找到main方法，整个ms-core没有启动入口。
但是它作为核心依赖jar包，又没有参与业务，所以没有给它提供main方法的启动类。
解决方法：
添加一个spring boot的启动类，添加一个main方法作为程序入口。
@SpringBootApplication
public class SpringCloudMsCoreApp {
public static void main(String[] args) {
SpringApplication.run(SpringCloudMsCoreApp.class, args);
}
}
重新打包即可！！！