1、为避免程序运行报错 ，需要在Application.class添加注解@MapperScan(mapper包位置)

@SpringBootApplication(scanBasePackages={"com.example.api","zd.test.server","zd.test.entity","zd.test.dal"})
//@SpringBootApplication
//@ComponentScan({"com.example.api","zd.test.server","zd.test.entity","zd.test.dal"})
@MapperScan("zd.test.dal")
public class ApiApplication {

    public static void main(String[] args) {
        SpringApplication.run(ApiApplication.class, args);
        System.out.println("res1:"+1);
    }

}

需用到的包-pom.xml：

        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis-spring</artifactId>
            <version>2.0.0</version>
        </dependency>

      <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.1.1</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>5.3.3</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.6</version>
        </dependency>

2、以上修改避免了运行时异常，但是问题依旧。

解决方法在每个mapper类前加上@Repository注解

@Repository
@Mapper//@Mapper注解 springbboot能否自动扫描识别
public interface UserMapper {
}

3、其他并不靠谱的解决方法：

• 修改@Autowired 为@Autowired(required = false)

required=false 设置这个属性后，mapper对象就可以为null ,这样无形之中给自己挖了个坑