日常开发SpringBoot项目启动类都用@SpringBootApplication，实际上它是下面三个注解的组合：
@EnableAutoConfiguration: enable Spring Boot’s auto-configuration mechanism@ComponentScan: enable@Componentscan on the package where the application is located (see the best practices)@Configuration: allow to register extra beans in the context or import additional configuration classes
启动慢往往跟@ComponentScan和@EnableAutoConfiguration加载的内容太多有关，一种方法是不用这两个注解，通过@import注解精确指定要加载扫描的类，但要加载的类多时又很麻烦，
可以用@SpringBootApplication注解下面的属性：
- exclude: Exclude the list of classes from the auto configuration.
- excludeNames: Exclude the list of fully qualified class names from the auto configuration. This parameter added since spring boot 1.3.0.
- scanBasePackageClasses: Provide the list of classes that has to be applied for the @ComponentScan.
- scanBasePackages Provide the list of packages that has to be applied for the @ComponentScan. This parameter added since spring boot 1.3.0.
另外，如果SpringBoot项目启动很慢，可能意味着你要重新拆分微服务。