SpringBoot之HelloWorld
首先创建一个Spring Initializr的项目
给Group和Artifact起名，HelloWorld项目就直接默认即可。
选择Web —> Spring Web
给Project起名称，默认就好，接着Finish
接下来Import Changes，项目的结构如下图所示：
接着在建立一个新的控制器文件HelloController.java
在该文件中添加代码
package com.example.demo.controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class HelloController {
@GetMapping(value = "/hello")
public String hello()
{
return "Hello SpringBoot";
}
}
运行DemoApplication
"C:\Program Files\Java\jdk1.8.0_161\bin\java.exe" -XX:TieredStopAtLevel=1 -noverify -Dspring.output.ansi.enabled=always -Dcom.sun.management.jmxremote -Dspring.jmx.enabled=true -Dspring.liveBeansView.mbeanDomain -Dspring.application.admin.enabled=true "-javaagent:G:\IDEA\main\IntelliJ IDEA 2019.1.1\lib\idea_rt.jar=57145:G:\IDEA\main\IntelliJ IDEA 2019.1.1\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files\Java\jdk1.8.0_161\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.8.0_161\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.8.0_161\jre\lib\ext\access-bridge-64.jar;C:\Program Files\Java\jdk1.8.0_161\jre\lib\ext\cldrdata.jar;C:\Program Files\Java\jdk1.8.0_161\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.8.0_161\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.8.0_161\jre\lib\ext\jfxrt.jar;C:\Program Files\Java\jdk1.8.0_161\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.8.0_161\jre\lib\ext\nashorn.jar;C:\Program Files\Java\jdk1.8.0_161\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.8.0_161\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.8.0_161\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.8.0_161\jre\lib\ext\sunpkcs11.jar;C:\Program Files\Java\jdk1.8.0_161\jre\lib\ext\zipfs.jar;C:\Program Files\Java\jdk1.8.0_161\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.8.0_161\jre\lib\jce.jar;C:\Program Files\Java\jdk1.8.0_161\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.8.0_161\jre\lib\jfxswt.jar;C:\Program Files\Java\jdk1.8.0_161\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.8.0_161\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.8.0_161\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.8.0_161\jre\lib\resources.jar;C:\Program Files\Java\jdk1.8.0_161\jre\lib\rt.jar;G:\IDEA\demo\target\classes;F:\maven\Repository\org\springframework\boot\spring-boot-starter-web\2.1.9.RELEASE\spring-boot-starter-web-2.1.9.RELEASE.jar;F:\maven\Repository\org\springframework\boot\spring-boot-starter\2.1.9.RELEASE\spring-boot-starter-2.1.9.RELEASE.jar;F:\maven\Repository\org\springframework\boot\spring-boot\2.1.9.RELEASE\spring-boot-2.1.9.RELEASE.jar;F:\maven\Repository\org\springframework\boot\spring-boot-autoconfigure\2.1.9.RELEASE\spring-boot-autoconfigure-2.1.9.RELEASE.jar;F:\maven\Repository\org\springframework\boot\spring-boot-starter-logging\2.1.9.RELEASE\spring-boot-starter-logging-2.1.9.RELEASE.jar;F:\maven\Repository\ch\qos\logback\logback-classic\1.2.3\logback-classic-1.2.3.jar;F:\maven\Repository\ch\qos\logback\logback-core\1.2.3\logback-core-1.2.3.jar;F:\maven\Repository\org\apache\logging\log4j\log4j-to-slf4j\2.11.2\log4j-to-slf4j-2.11.2.jar;F:\maven\Repository\org\apache\logging\log4j\log4j-api\2.11.2\log4j-api-2.11.2.jar;F:\maven\Repository\org\slf4j\jul-to-slf4j\1.7.28\jul-to-slf4j-1.7.28.jar;F:\maven\Repository\javax\annotation\javax.annotation-api\1.3.2\javax.annotation-api-1.3.2.jar;F:\maven\Repository\org\yaml\snakeyaml\1.23\snakeyaml-1.23.jar;F:\maven\Repository\org\springframework\boot\spring-boot-starter-json\2.1.9.RELEASE\spring-boot-starter-json-2.1.9.RELEASE.jar;F:\maven\Repository\com\fasterxml\jackson\core\jackson-databind\2.9.9.3\jackson-databind-2.9.9.3.jar;F:\maven\Repository\com\fasterxml\jackson\core\jackson-annotations\2.9.0\jackson-annotations-2.9.0.jar;F:\maven\Repository\com\fasterxml\jackson\core\jackson-core\2.9.9\jackson-core-2.9.9.jar;F:\maven\Repository\com\fasterxml\jackson\datatype\jackson-datatype-jdk8\2.9.9\jackson-datatype-jdk8-2.9.9.jar;F:\maven\Repository\com\fasterxml\jackson\datatype\jackson-datatype-jsr310\2.9.9\jackson-datatype-jsr310-2.9.9.jar;F:\maven\Repository\com\fasterxml\jackson\module\jackson-module-parameter-names\2.9.9\jackson-module-parameter-names-2.9.9.jar;F:\maven\Repository\org\springframework\boot\spring-boot-starter-tomcat\2.1.9.RELEASE\spring-boot-starter-tomcat-2.1.9.RELEASE.jar;F:\maven\Repository\org\apache\tomcat\embed\tomcat-embed-core\9.0.26\tomcat-embed-core-9.0.26.jar;F:\maven\Repository\org\apache\tomcat\embed\tomcat-embed-el\9.0.26\tomcat-embed-el-9.0.26.jar;F:\maven\Repository\org\apache\tomcat\embed\tomcat-embed-websocket\9.0.26\tomcat-embed-websocket-9.0.26.jar;F:\maven\Repository\org\hibernate\validator\hibernate-validator\6.0.17.Final\hibernate-validator-6.0.17.Final.jar;F:\maven\Repository\javax\validation\validation-api\2.0.1.Final\validation-api-2.0.1.Final.jar;F:\maven\Repository\org\jboss\logging\jboss-logging\3.3.3.Final\jboss-logging-3.3.3.Final.jar;F:\maven\Repository\com\fasterxml\classmate\1.4.0\classmate-1.4.0.jar;F:\maven\Repository\org\springframework\spring-web\5.1.10.RELEASE\spring-web-5.1.10.RELEASE.jar;F:\maven\Repository\org\springframework\spring-beans\5.1.10.RELEASE\spring-beans-5.1.10.RELEASE.jar;F:\maven\Repository\org\springframework\spring-webmvc\5.1.10.RELEASE\spring-webmvc-5.1.10.RELEASE.jar;F:\maven\Repository\org\springframework\spring-aop\5.1.10.RELEASE\spring-aop-5.1.10.RELEASE.jar;F:\maven\Repository\org\springframework\spring-context\5.1.10.RELEASE\spring-context-5.1.10.RELEASE.jar;F:\maven\Repository\org\springframework\spring-expression\5.1.10.RELEASE\spring-expression-5.1.10.RELEASE.jar;F:\maven\Repository\org\slf4j\slf4j-api\1.7.28\slf4j-api-1.7.28.jar;F:\maven\Repository\org\springframework\spring-core\5.1.10.RELEASE\spring-core-5.1.10.RELEASE.jar;F:\maven\Repository\org\springframework\spring-jcl\5.1.10.RELEASE\spring-jcl-5.1.10.RELEASE.jar" com.example.demo.DemoApplication . ____ _ __ _ _ /\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \ ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \ \\/ ___)| |_)| | | | | || (_| | ) ) ) ) ' |____| .__|_| |_|_| |_\__, | / / / / =========|_|==============|___/=/_/_/_/ :: Spring Boot :: (v2.1.9.RELEASE) 2019-10-30 12:19:08.662 INFO 8128 --- [ main] com.example.demo.DemoApplication : Starting DemoApplication on DESKTOP-T849CU0 with PID 8128 (G:\IDEA\demo\target\classes started by wym in G:\IDEA\demo) 2019-10-30 12:19:08.690 INFO 8128 --- [ main] com.example.demo.DemoApplication : No active profile set, falling back to default profiles: default 2019-10-30 12:19:13.139 INFO 8128 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http) 2019-10-30 12:19:13.226 INFO 8128 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat] 2019-10-30 12:19:13.227 INFO 8128 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.26] 2019-10-30 12:19:13.242 INFO 8128 --- [ main] o.a.catalina.core.AprLifecycleListener : An older version [1.2.21] of the APR based Apache Tomcat Native library is installed, while Tomcat recommends a minimum version of [1.2.23] 2019-10-30 12:19:13.242 INFO 8128 --- [ main] o.a.catalina.core.AprLifecycleListener : Loaded APR based Apache Tomcat Native library [1.2.21] using APR version [1.6.5]. 2019-10-30 12:19:13.242 INFO 8128 --- [ main] o.a.catalina.core.AprLifecycleListener : APR capabilities: IPv6 [true], sendfile [true], accept filters [false], random [true]. 2019-10-30 12:19:13.243 INFO 8128 --- [ main] o.a.catalina.core.AprLifecycleListener : APR/OpenSSL configuration: useAprConnector [false], useOpenSSL [true] 2019-10-30 12:19:13.334 INFO 8128 --- [ main] o.a.catalina.core.AprLifecycleListener : OpenSSL successfully initialized [OpenSSL 1.1.1a 20 Nov 2018] 2019-10-30 12:19:13.594 INFO 8128 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext 2019-10-30 12:19:13.594 INFO 8128 --- [ main] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 4713 ms 2019-10-30 12:19:14.195 INFO 8128 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 'applicationTaskExecutor' 2019-10-30 12:19:14.594 INFO 8128 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path '' 2019-10-30 12:19:14.601 INFO 8128 --- [ main] com.example.demo.DemoApplication : Started DemoApplication in 8.051 seconds (JVM running for 14.462) 2019-10-30 12:20:53.101 INFO 8128 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring DispatcherServlet 'dispatcherServlet' 2019-10-30 12:20:53.101 INFO 8128 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : Initializing Servlet 'dispatcherServlet' 2019-10-30 12:20:53.116 INFO 8128 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : Completed initialization in 15 ms
运行成功后，浏览器中输入http://localhost:8080/hello
从上面的过程和SSM搭建HelloWorld项目的对比来看，SpringBoot不必配置任何xml文件，过程大大简化，使得程序员能够更加专注于程序的业务逻辑。Springboot甚至内置了tomcat，也不需要我们手动配置。
