开始搭建Springboot

1创建maven工程，加入依赖

https://start.spring.io/ 可以生成依赖配置

Pom文件中加入：

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.2.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

2编写Controller和Application class

D:\springbootdemo\src\main\java\cn\greenleaf\controller\HelloController.java：

package controller;

import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.bind.annotation.RequestMapping;


@RestController
public class HelloController {
    @RequestMapping("/")
    public String Homepage(){
        return "hello";
    }
}

D:\springbootdemo\src\main\java\cn\greenleaf\Application.java：

package cn.greenleaf;

import java.util.Arrays;

import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.Bean;

@SpringBootApplication
public class Application {

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

    @Bean
    public CommandLineRunner commandLineRunner(ApplicationContext ctx) {
        return args -> {

            System.out.println("Let's inspect the beans provided by Spring Boot:");

            String[] beanNames = ctx.getBeanDefinitionNames();
            Arrays.sort(beanNames);
            for (String beanName : beanNames) {
                System.out.println(beanName);
            }

        };
    }

}

3运行

运行Application的main方法，或者在pom文件所在目录：

./mvnw spring-boot:run

或者 mvn spring-boot:run

常见问题

1. application.java 文件不能直接放在main/java文件夹下，必须要建一个包把他放进去
   否则会有如下报错：

** WARNING ** : Your ApplicationContext is unlikely to start due to a @ComponentScan of the default

2.IDEA启动用手机无法访问，命令行可以?

参考

https://spring.io/guides/gs/spring-boot/