1. Code implementation

1.1 Create Maven Project

Create Maven project using idea:
Insert picture description here
Enter GroupId and ArtifactId:

Next step

1.2 Add SpringBoot's starting dependency

Add start dependency in pom.xml

 	<parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.0.RELEASE</version>
    </parent>

Add springMVC dependency

1.3 Add Springboot boot class

package com.freedom;

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

@SpringBootApplication
public class MySpringBootApplication {
    public static void main(String[] args) {
        SpringApplication.run(MySpringBootApplication.class);
    }
}

1.4 Write Controller

package com.freedom.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
public class DemoController {
    
    @RequestMapping("/demo")
    @ResponseBody
    public String quick() {
        return "springboot-demo 访问成功!";
    }
}

1.5 Test

Start the test class, view the startup log


  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.2.0.RELEASE)

2019-11-07 21:53:21.790  INFO 16736 --- [           main] com.freedom.MySpringBootApplication      : Starting MySpringBootApplication on To-be-better with PID 16736 (E:\11_ideaworkspace\springboot-demo\target\classes started by wiljz in E:\11_ideaworkspace\springboot-demo)
2019-11-07 21:53:21.795  INFO 16736 --- [           main] com.freedom.MySpringBootApplication      : No active profile set, falling back to default profiles: default
2019-11-07 21:53:26.499  INFO 16736 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2019-11-07 21:53:26.536  INFO 16736 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2019-11-07 21:53:26.536  INFO 16736 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.27]
2019-11-07 21:53:26.791  INFO 16736 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2019-11-07 21:53:26.791  INFO 16736 --- [           main] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 4695 ms
2019-11-07 21:53:27.100  INFO 16736 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
2019-11-07 21:53:27.466  INFO 16736 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2019-11-07 21:53:27.469  INFO 16736 --- [           main] com.freedom.MySpringBootApplication      : Started MySpringBootApplication in 7.905 seconds (JVM running for 9.323)
2019-11-07 21:53:45.936  INFO 16736 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring DispatcherServlet 'dispatcherServlet'
2019-11-07 21:53:45.936  INFO 16736 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Initializing Servlet 'dispatcherServlet'
2019-11-07 21:53:45.941  INFO 16736 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Completed initialization in 5 ms

Input: http: // localhost: 8080 / demo
display
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2. Quick start analysis

@SpringBootApplication: Annotate the startup class of SpringBoot, the annotation has multiple functions (detailed analysis later)
SpringApplication.run (MySpringBootApplication.class) represents the startup class that runs SpringBoot, and the parameter is
the bytecode object of the SpringBoot startup class

3. Hot deployment

After the code is modified, it takes effect without restarting, which is called hot deployment. Add in pom.xml

<!--热部署配置-->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-devtools</artifactId>
    </dependency>