背景：
maven版springboot web 项目，pom.xml 中设置了 <packaging>pom</packaging>
现象：
2021-01-14 19:59:53.752 WARN 18580 --- [ main] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'apiController': Unsatisfied dependency expressed through field 'userService'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'userService': Unsatisfied dependency expressed through field 'userMapper'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'userMapper' defined in file [C:\Users\xgz\Desktop\gitee\rest-server\target\classes\com\fu\dao\UserMapper.class]: Unsatisfied dependency expressed through bean property 'sqlSessionFactory'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'sqlSessionFactory' defined in class path resource [org/mybatis/spring/boot/autoconfigure/MybatisAutoConfiguration.class]: Unsatisfied dependency expressed through method 'sqlSessionFactory' parameter 0; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSource' defined in class path resource [org/springframework/boot/autoconfigure/jdbc/DataSourceConfigurationDataSourceBeanCreationException: Failed to determine a suitable driver class
2021-01-14 19:59:53.759 INFO 18580 --- [ main] o.apache.catalina.core.StandardService : Stopping service [Tomcat]
2021-01-14 19:59:53.784 INFO 18580 --- [ main] ConditionEvaluationReportLoggingListener :

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2021-01-14 19:59:53.797 ERROR 18580 --- [ main] o.s.b.d.LoggingFailureAnalysisReporter :

APPLICATION FAILED TO START

Description:

Failed to configure a DataSource: 'url' attribute is not specified and no embedded datasource could be configured.

Reason: Failed to determine a suitable driver class

Action:

Consider the following:
If you want an embedded database (H2, HSQL or Derby), please put it on the classpath.
If you have database settings to be loaded from a particular profile you may need to activate it (no profiles are currently active).

Process finished with exit code 1

解决办法：
<packaging>pom</packaging> 改为 <packaging>jar</packaging>