springboot系列一 第一個restful接口 main方法啓動 jar包啓動 mvn啓動(2.1.0.RELEASE版本)

springboot官方文檔

https://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#_working_with_spring_boot

maven依賴

spring-boot-starter-parent

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>

	<groupId>com.example</groupId>
	<artifactId>myproject</artifactId>
	<version>0.0.1-SNAPSHOT</version>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.1.0.RELEASE</version>
	</parent>

	<!-- Additional lines to be added here... -->

</project>

web依賴

<dependencies>
	<dependency>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-web</artifactId>
	</dependency>
</dependencies>

啓動類和接口

@RestController
@EnableAutoConfiguration
public class HelloWorldApp {

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

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

註解解釋

@RestController

@RestController = @Controller + @ResponseBody

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Controller //springmvc的註解
@ResponseBody //springmvc的註解
public @interface RestController {
    @AliasFor(
        annotation = Controller.class
    )
    String value() default "";
}

官方文檔解釋

The @RestController and @RequestMapping annotations are Spring MVC annotations. (They are not specific to Spring Boot.)
解釋： @RestController 和 @RequestMapping 是springmvc的註解，沒什麼特殊性

@EnableAutoConfiguration

This annotation tells Spring Boot to 「guess」 how you want to configure Spring, based on the jar dependencies that you have added. Since spring-boot-starter-web added Tomcat and Spring MVC, the auto-configuration assumes that you are developing a web application and sets up Spring accordingly.
@EnableAutoConfiguration 猜想地給開發者配置好有關springmvc、tomcat、spring方面的配置。也就是會自動配置好springmvc、tomcat、spring的一些配置

啓動服務和訪問接口

啓動main方法，控制檯打印：

.   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.1.0.RELEASE)

2018-11-21 15:03:33.622  INFO 75693 --- [           main] com.yimingkeji.helloworld.HelloWorldApp  : Starting HelloWorldApp on yangzhenlongdeMacBook-Pro.local with PID 75693 (/Users/yangzhenlong/projs/my/yimingkeji/springboot/helloword/target/classes started by yangzhenlong in /Users/yangzhenlong/projs/my/yimingkeji/springboot)
2018-11-21 15:03:33.626  INFO 75693 --- [           main] com.yimingkeji.helloworld.HelloWorldApp  : No active profile set, falling back to default profiles: default
2018-11-21 15:03:34.499  INFO 75693 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2018-11-21 15:03:34.516  INFO 75693 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2018-11-21 15:03:34.516  INFO 75693 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet Engine: Apache Tomcat/9.0.12
2018-11-21 15:03:34.522  INFO 75693 --- [           main] o.a.catalina.core.AprLifecycleListener   : The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path: [/Users/yangzhenlong/Library/Java/Extensions:/Library/Java/Extensions:/Network/Library/Java/Extensions:/System/Library/Java/Extensions:/usr/lib/java:.]
2018-11-21 15:03:34.581  INFO 75693 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2018-11-21 15:03:34.582  INFO 75693 --- [           main] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 917 ms
2018-11-21 15:03:34.604  INFO 75693 --- [           main] o.s.b.w.servlet.ServletRegistrationBean  : Servlet dispatcherServlet mapped to [/]
2018-11-21 15:03:34.607  INFO 75693 --- [           main] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'characterEncodingFilter' to: [/*]
2018-11-21 15:03:34.608  INFO 75693 --- [           main] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
2018-11-21 15:03:34.608  INFO 75693 --- [           main] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'formContentFilter' to: [/*]
2018-11-21 15:03:34.608  INFO 75693 --- [           main] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'requestContextFilter' to: [/*]
2018-11-21 15:03:34.763  INFO 75693 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
2018-11-21 15:03:34.933  INFO 75693 --- [           main]
o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2018-11-21 15:03:34.936  INFO 75693 --- [           main] com.yimingkeji.helloworld.HelloWorldApp  : Started HelloWorldApp in 1.727 seconds (JVM running for 2.849)

日誌中看到 項目啓動端口(prot)爲8080，啓動根路徑(path)爲' '

瀏覽器或者http客戶端（如postman）訪問 localhost:8080

Hello World!

使用jar包啓動

在pom.xml依賴中添加spring-boot-maven-plugin插件

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

在終端shell或者Terminal中執行命令：

$ mvn package

在項目target目錄下會生成jar包：

啓動jar包

$ java -jar target/helloword-1.0.0-SNAPSHOT.jar 
2018-11-21 15:12:35.077  INFO 75841 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
2018-11-21 15:12:35.355  INFO 75841 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2018-11-21 15:12:35.359  INFO 75841 --- [           main] com.yimingkeji.helloworld.HelloWorldApp  : Started HelloWorldApp in 2.382 seconds (JVM running for 2.838)

訪問 localhost:8080

Hello World!

按 Ctrl + C 結束服務。

使用mvn啓動

$ mvn spring-boot:run

項目地址

https://gitee.com/yimingkeji/springboot