一、@EnableAutoConfiguration
The second class-level annotation is @EnableAutoConfiguration. This annotation tells Spring Boot to “guess” how you
will want to configure Spring, based on the jar dependencies that you have added. Since spring-boot-starter-web added Tomcat and Spring MVC,
the auto-configuration will assume that you are developing a web application and setup Spring accordingly.
Starters and Auto-Configuration Auto-configuration is designed to work well with “Starters”, but the two concepts are not directly tied.
You are free to pick-and-choose jar dependencies outside of the starters and Spring Boot will still do
its best to auto-configure your application.
这个注释告诉SpringBoot“猜”你将如何想配置Spring,基于你已经添加jar依赖项。如果spring-boot-starter-web已经添加Tomcat和Spring MVC,这个注释自动将假设您正在开发一个web应用程序并添加相应的spring设置。
自动配置被设计用来和“Starters”一起更好的工作,但这两个概念并不直接相关。您可以自由挑选starter依赖项以外的jar包，springboot仍将尽力自动配置您的应用程序。
spring通常建议我们将main方法所在的类放到一个root包下，@EnableAutoConfiguration（开启自动配置）注解通常都放到main所在类的上面，下面是一个典型的结构布局：
com
+- example
+- myproject
+- Application.java
|
+- domain
| +- Customer.java
| +- CustomerRepository.java
|
+- service
| +- CustomerService.java
|
+- web
+- CustomerController.java
这样@EnableAutoConfiguration可以从逐层的往下搜索各个加注解的类，例如，你正在编写一个JPA程序（如果你的pom里进行了配置的话），spring会自动去搜索加了@Entity注解的类，并进行调用
二、@SpringbootApplication
使用@SpringbootApplication注解 可以解决根类或者配置类（我自己的说法，就是main所在类）头上注解过多的问题，一个@SpringbootApplication相当于@Configuration,@EnableAutoConfiguration和 @ComponentScan 并具有他们的默认属性值
package com.example.myproject;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}