Demo Application

SpringBootApplication

The main class is specified by annotating it with @SpringBootApplication. Create a file named “DemoApplication.groovy” in the com.example.demo package, and put the following:

package com.example.demo

import org.springframework.boot.SpringApplication
import org.springframework.boot.autoconfigure.SpringBootApplication


@SpringBootApplication
class DemoApplication {
      static void main(String[] args) {
         SpringApplication.run DemoApplication, args //1
      }
      @Bean
      Service sampleServier() { new SampleService() } //2
}

1. The main method calls SpringApplication.run to start the application.
2. Beans can be created directly using the @Bean annotation on methods

The @SpringBootApplication annotation tells Spring a number of things:

1. To use auto-configuration.
2. To use component scanning. Scanning all packages for classes annotated with Spring annotations.
3. This class is a Java-based configuration class, so you can define beans here using the @Bean annotation on a method that returns a bean.

Alternatively, if you want to specify web-service mappings more directly, you can use the @Controller and @RequestMapping annotations like the following, hello/SampleController.java:

package hello;

import org.springframework.boot.*;
import org.springframework.boot.autoconfigure.*;
import org.springframework.stereotype.*;
import org.springframework.web.bind.annotation.*;

@Controller
@EnableAutoConfiguration
public class SampleController {

    @RequestMapping("/")
    @ResponseBody
    String home() {
     return "Hello World!";
    }

    public static void main(String[] args) throws Exception {
      SpringApplication.run(SampleController.class, args);
    }
}

Of course, this would be a much smaller application. For larger projects, you should use the @SpringBootApplication approach.