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.
這個注釋告訴SpringBoot“猜”你將如何想配置Spring,基於你已經添加jar依賴項。如果spring-boot-starter-web已經添加Tomcat和Spring MVC,這個注釋自動將假設您正在開發一個web應用程序並添加相應的spring設置。
自動配置被設計用來和“Starters”一起更好的工作,但這兩個概念並不直接相關。您可以自由挑選starter依賴項以外的jar包，springboot仍將盡力自動配置您的應用程序。
spring通常建議我們將main方法所在的類放到一個root包下，@EnableAutoConfiguration（開啟自動配置）注解通常都放到main所在類的上面，下面是一個典型的結構布局：
com
+- example
+- myproject
+- Application.java
|
+- domain
| +- Customer.java
| +- CustomerRepository.java
|
+- service
| +- CustomerService.java
|
+- web
+- CustomerController.java
這樣@EnableAutoConfiguration可以從逐層的往下搜索各個加注解的類，例如，你正在編寫一個JPA程序（如果你的pom里進行了配置的話），spring會自動去搜索加了@Entity注解的類，並進行調用
二、@SpringbootApplication
使用@SpringbootApplication注解 可以解決根類或者配置類（我自己的說法，就是main所在類）頭上注解過多的問題，一個@SpringbootApplication相當於@Configuration,@EnableAutoConfiguration和 @ComponentScan 並具有他們的默認屬性值
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);
}
}