启动报错：

[root@node05 nginx]# java -jar demo-1.0.0-SNAPSHOT.jar 

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.1.7.RELEASE)

2022-05-27 16:48:54.483  INFO 2184 --- [           main] com.example.demo.DemoApplication         : Starting DemoApplication v1.0.0-SNAPSHOT on node05 with PID 2184 (/opt/nginx/demo-1.0.0-SNAPSHOT.jar started by root in /opt/nginx)
2022-05-27 16:48:54.507  INFO 2184 --- [           main] com.example.demo.DemoApplication         : No active profile set, falling back to default profiles: default
2022-05-27 16:48:56.849  INFO 2184 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2022-05-27 16:48:56.907  INFO 2184 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2022-05-27 16:48:56.908  INFO 2184 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.22]
2022-05-27 16:48:57.428  INFO 2184 --- [           main] org.apache.jasper.servlet.TldScanner     : At least one JAR was scanned for TLDs yet contained no TLDs. Enable debug logging for this logger for a complete list of JARs that were scanned but no TLDs were found in them. Skipping unneeded JARs during scanning can improve startup time and JSP compilation time.
2022-05-27 16:48:57.925  INFO 2184 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2022-05-27 16:48:57.925  INFO 2184 --- [           main] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 3335 ms
2022-05-27 16:48:58.152  WARN 2184 --- [           main] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'testController': Unsatisfied dependency expressed through field 'userService'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userService': Injection of resource dependencies failed; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'userDao' defined in URL [jar:file:/opt/nginx/demo-1.0.0-SNAPSHOT.jar!/BOOT-INF/classes!/com/example/demo/dao/UserDao.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/DataSourceConfiguration$Hikari.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.zaxxer.hikari.HikariDataSource]: Factory method 'dataSource' threw exception; nested exception is org.springframework.boot.autoconfigure.jdbc.DataSourceProperties$DataSourceBeanCreationException: Failed to determine a suitable driver class
2022-05-27 16:48:58.154  INFO 2184 --- [           main] o.apache.catalina.core.StandardService   : Stopping service [Tomcat]
2022-05-27 16:48:58.211  INFO 2184 --- [           main] ConditionEvaluationReportLoggingListener : 

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2022-05-27 16:48:58.212 ERROR 2184 --- [           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).

解决办法：

1、如果不需要数据库，把数据源去掉：

//去掉数据源，只需要添加：exclude = DataSourceAutoConfiguration.class
@SpringBootApplication(exclude = DataSourceAutoConfiguration.class)
public class DemoApplication {

  public static void main(String[] args) {
    SpringApplication.run(DemoApplication.class, args);
  }

}

2、如果有数据库，看第二种：

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
            <!--这里写上main方法所在类的路径-->
            <configuration>
                <mainClass>com.example.demo.DemoApplication</mainClass>
            </configuration>
            <executions>
                <execution>
                    <goals>
                        <goal>repackage</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
    <resources>
        <resource>
            <directory>src/main/java</directory>
            <includes>
                <include>**/*.properties</include>
                <include>**/*.xml</include>
            </includes>
            <filtering>true</filtering>
        </resource>
        <resource>
            <directory>src/main/resources</directory>
            <includes>
                <include>*</include>
                <include>*/*</include>
            </includes>
            <filtering>true</filtering>
        </resource>
        <resource>
            <directory>src/main/webapp</directory>
            <targetPath>META-INF/resources</targetPath>
            <includes>
                <include>**/**</include>
            </includes>
        </resource>
    </resources>

</build>

一定要把配置文件编译进去：

没添加前执行打包的图：

 没有把配置文件打包进来，所以报错了

 添加了<build>标签打包后：