To finish our application, we need to create a single Java file. By default, Maven compiles sources from src/main/java, so you need to create that folder structure and then add a file named src/main/java/Example.java to contain the following code: 为了完成应用程序， 需要创建一个Java文件。 默认情况下， Maven从src/main/java（目录）下编译源码， 因此需要创建那文件夹结构，然后添加一个名叫src/main/java/Example.java的文件， 文件内容包含如下代码：

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


@RestController
@EnableAutoConfiguration
public class Example {


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


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


}

Although there is not much code here, quite a lot is going on. We step through the important parts in the next few sections. 尽管这儿没有太多代码， 但是很多代码在进行中。 在接下来的几节中，我们将逐步了解重要的部分。