springboot项目如何打war包流程的方法

<!--添加servlet-api的依赖,用来打war包 -->
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <scope>provided</scope>
    </dependency>

<!--最终打成war包，排除内置的tomcat-->
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
      <exclusions>
        <exclusion>
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-starter-tomcat</artifactId>
        </exclusion>
      </exclusions>
    </dependency>

 <dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-tomcat</artifactId>
   <scope>provided</scope>
</dependency>

@SpringBootApplication
public class MainApp {

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

@SpringBootApplication
public class MainApp extends SpringBootServletInitializer {

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

  @Override
  protected SpringApplicationBuilder configure(SpringApplicationBuilder builder) {
    return builder.sources(MainApp.class);
  }
}

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