专车介绍
该趟专车是开往 SpringBoot 应用启动方式的实战专车，主要讲解通过多种方式来启动 SpringBoot 应用
专车问题
第一个问题：SpringBoot 可以通过哪些方式来启动应用
专车实战
本实战示例以 boot-example-web 模块为样例代码
方式一：通过 main 函数来启动 SpringBoot 应用
@SpringBootApplication
public class WebApplication {
public static void main(String[] args) {
SpringApplication.run(WebApplication.class, args);
}
}直接运行如上的 main 函数，就可以启动我们的应用，看到如下日志展示，说明应用启动成功
2019-10-22 09:52:40.425 INFO 7086 --- [ main] com.boot.example.WebApplication : No active profile set, falling back to default profiles: default
2019-10-22 09:52:41.561 INFO 7086 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http)
2019-10-22 09:52:41.587 INFO 7086 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
2019-10-22 09:52:41.588 INFO 7086 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.21]
2019-10-22 09:52:41.697 INFO 7086 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2019-10-22 09:52:41.697 INFO 7086 --- [ main] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 1224 ms
2019-10-22 09:52:41.950 INFO 7086 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 'applicationTaskExecutor'
2019-10-22 09:52:42.104 INFO 7086 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''
2019-10-22 09:52:42.107 INFO 7086 --- [ main] com.boot.example.WebApplication : Started WebApplication in 2.0 seconds (JVM running for 2.537)
2019-10-22 09:52:50.136 INFO 7086 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring DispatcherServlet 'dispatcherServlet'
2019-10-22 09:52:50.136 INFO 7086 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : Initializing Servlet 'dispatcherServlet'
2019-10-22 09:52:50.141 INFO 7086 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : Completed initialization in 5 ms如果启动失败，可以查看具体日志信息，看看是否端口被占用，端口占用错误信息
Caused by: java.net.BindException: Address already in use方式二：通过 maven 的方式来启动 SpringBoot 应用
首先需要添加 SpringBoot maven 插件
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>执行如下命令：
? boot-example git:(master) ? cd boot-example-web
? boot-example-web git:(master) ? mvn spring-boot:run如果启动成功可以看到如下日志信息：
[INFO] Scanning for projects...
[INFO]
[INFO] -----------------< com.boot.example:boot-example-web >------------------
[INFO] Building boot-example-web 1.0-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] >>> spring-boot-maven-plugin:2.1.6.RELEASE:run (default-cli) > test-compile @ boot-example-web >>>
[INFO]
[INFO] --- maven-resources-plugin:3.0.2:resources (default-resources) @ boot-example-web ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory /Users/pengli/software/idea/workspace/boot-example/boot-example-web/src/main/resources
[INFO]
[INFO] --- maven-compiler-plugin:3.2:compile (default-compile) @ boot-example-web ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 5 source files to /Users/pengli/software/idea/workspace/boot-example/boot-example-web/target/classes
[INFO]
[INFO] --- maven-resources-plugin:3.0.2:testResources (default-testResources) @ boot-example-web ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory /Users/pengli/software/idea/workspace/boot-example/boot-example-web/src/test/resources
[INFO]
[INFO] --- maven-compiler-plugin:3.2:testCompile (default-testCompile) @ boot-example-web ---
[INFO] No sources to compile
[INFO]
[INFO] <<< spring-boot-maven-plugin:2.1.6.RELEASE:run (default-cli) < test-compile @ boot-example-web <<<
[INFO]
[INFO]
[INFO] --- spring-boot-maven-plugin:2.1.6.RELEASE:run (default-cli) @ boot-example-web ---
. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v2.1.6.RELEASE)
2019-10-22 09:56:12.163 INFO 7249 --- [ main] com.boot.example.WebApplication : Starting WebApplication on pengdeMacBook-Pro.local with PID 7249 (....../workspace/boot-example/boot-example-web/target/classes started by pengli in ......./workspace/boot-example/boot-example-web)
2019-10-22 09:56:12.166 INFO 7249 --- [ main] com.boot.example.WebApplication : No active profile set, falling back to default profiles: default
2019-10-22 09:56:13.296 INFO 7249 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http)
2019-10-22 09:56:13.332 INFO 7249 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
2019-10-22 09:56:13.332 INFO 7249 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.21]
2019-10-22 09:56:13.445 INFO 7249 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2019-10-22 09:56:13.446 INFO 7249 --- [ main] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 1232 ms
2019-10-22 09:56:13.689 INFO 7249 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 'applicationTaskExecutor'
2019-10-22 09:56:13.949 INFO 7249 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''
2019-10-22 09:56:13.953 INFO 7249 --- [ main] com.boot.example.WebApplication : Started WebApplication in 2.277 seconds (JVM running for 6.671)
2019-10-22 09:56:21.437 INFO 7249 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring DispatcherServlet 'dispatcherServlet'方式三：以 jar 包的方式启动
在控制台下执行如下面命令：
? boot-example-web git:(master) ? mvn clean package -X再依次执行如下命令：
? boot-example-web git:(master) ? cd target
? target git:(master) ? ls
boot-example-web-1.0-SNAPSHOT.jar generated-sources maven-status
classes maven-archiver
? target git:(master) ? java -jar boot-example-web-1.0-SNAPSHOT.jar理想的情况下，我们的 SpringBoot 应用应该可以启动起来，但是实际下回看到如下错误：
boot-example-web-1.0-SNAPSHOT.jar中没有主清单属性解决方法：在上面的插件中添加额外的配置信息
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<executions>
<execution>
<goals>
<goal>repackage</goal>
<goal>build-info</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>然后重新打包，重新运行
? target git:(master) ? java -jar boot-example-web-1.0-SNAPSHOT.jar
. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v2.1.6.RELEASE)
2019-10-22 10:04:56.007 INFO 7497 --- [ main] com.boot.example.WebApplication : Starting WebApplication on .... with PID 7497 (...../boot-example/boot-example-web/target/boot-example-web-1.0-SNAPSHOT.jar started by pengli in ...../boot-example/boot-example-web/target)
2019-10-22 10:04:56.010 INFO 7497 --- [ main] com.boot.example.WebApplication : No active profile set, falling back to default profiles: default
2019-10-22 10:04:57.143 INFO 7497 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http)
2019-10-22 10:04:57.170 INFO 7497 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
2019-10-22 10:04:57.170 INFO 7497 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.21]
2019-10-22 10:04:57.271 INFO 7497 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2019-10-22 10:04:57.271 INFO 7497 --- [ main] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 1221 ms
2019-10-22 10:04:57.508 INFO 7497 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 'applicationTaskExecutor'
2019-10-22 10:04:57.765 INFO 7497 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''
2019-10-22 10:04:57.769 INFO 7497 --- [ main] com.boot.example.WebApplication : Started WebApplication in 2.134 seconds (JVM running for 2.526)
2019-10-22 10:05:00.280 INFO 7497 --- [nio-8080-exec-2] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring DispatcherServlet 'dispatcherServlet'
2019-10-22 10:05:00.280 INFO 7497 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet : Initializing Servlet 'dispatcherServlet'
2019-10-22 10:05:00.285 INFO 7497 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet : Completed initialization in 5 ms可以看到添加配置之后，SpringBoot 应用就可以正常的启动了，接下来我们来看看官方针对新增配置的一个说明：
repackage: create a jar or war file that is auto-executable. It can replace the regular artifact or can be attached to the build lifecycle with a separate classifier.
官方的大致意思就是：repackage 命令可以创建一个可自动执行的 jar 或者 war。它可以替换常规工件，或者可以使用单独的分类器附加到构建生命周期。
专车总结
SpringBoot 应用可以通过 main 函数、mvn 插件、jar 包这三种方式进行启动。使用 jar 方式启动，一定要在插件中配置 repackage