Spring boot 梳理

1. Spring boot 对代码结构无特殊要求，但有个套最佳实践的推荐
   1. 不要使用没有包名的类。没有包名时，@ComponentScan, @EntityScan, or @SpringBootApplication 可能会有问题。
   2. Main类在包路径中的位置：强烈建议main类放在包的根路径上。We generally recommend that you locate your main application class in a root package above other classes. The @SpringBootApplication annotation is often placed on your main class, and it implicitly defines a base “search package” for certain items. For example, if you are writing a JPA application, the package of the @SpringBootApplication annotated class is used to search for @Entity items. Using a root package also allows component scan to apply only on your project.

      1. com
          +- example
              +- myapplication
                  +- Application.java
                  |
                  +- customer
                  |   +- Customer.java
                  |   +- CustomerController.java
                  |   +- CustomerService.java
                  |   +- CustomerRepository.java
                  |
                  +- order
                      +- Order.java
                      +- OrderController.java
                      +- OrderService.java
                      +- OrderRepository.java

   3. The Application.java file would declare the main method, along with the basic @SpringBootApplication, as follows:

      1. package com.example.myapplication;
         
         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);
             }
         
         }

   4. @RestController
      @EnableAutoConfiguration
      public class App 
      {
          @RequestMapping("/hello")
          public HashMap<String,String> hello(){
              HashMap<String,String> result=new HashMap<String,String>();
              result.put("name", "jt");
              return result;
              
          }
          public static void main( String[] args )
          {
              SpringApplication.run(App.class, args);
          }
      }