@EnableAutoConfiguration和@SpringbootApplication注解

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);
    }

}