Spring Boot: Building a RESTful Web Service

1、@RestController：
which marks the class as a controller where every method returns a domain object instead of a view. It’s shorthand for @Controller and @ResponseBody rolled together.

2、在springBoot的controller中返回一个对象，不需要手动转换为json，因为会自动转换：
Because Jackson 2 is on the classpath, Spring’s MappingJackson2HttpMessageConverter is automatically chosen to convert the Greeting instance to JSON.

3、@SpringBootApplication注解综合了如下几个注解的功能
@Configuration tags the class as a source of bean definitions for the application context.
@EnableAutoConfiguration tells Spring Boot to start adding beans based on classpath settings, other beans, and various property settings.
Normally you would add @EnableWebMvc for a Spring MVC app, but Spring Boot adds it automatically when it sees spring-webmvc on the classpath. This flags the application as a web application and activates key behaviors such as setting up a DispatcherServlet.
@ComponentScan tells Spring to look for other components, configurations, and services in the hello package, allowing it to find the controllers.（注意：这里的英文注释中hello这个包，是springBoot的main方法中使用@SpringBootApplication注解类所在的包，也就是说，会自动扫描，但是只会扫描此包下以及子包下的类，所有会报错）

4、Build an executable JAR

1. 如何将项目打包为一个jar文件：If you are using Maven, you can run the application using mvn spring-boot:run. Or you can build the JAR file with mvn clean package，Then you can run the JAR file:
   java -jar target/gs-rest-service-0.1.0.jar