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

（3）注释掉自带的内部tomcat

在pom.xml里找到spring-boot-starter-web依赖节点，将<exclusions></exclusions>之间的内容删除

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
    <!-- 移除嵌入式tomcat插件 -->
    <exclusions>
        <exclusion>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
        </exclusion>
    </exclusions>
</dependency>

（4）在plugins中添加下面依赖

<plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-war-plugin</artifactId>
                <version>3.0.0</version>
                <configuration>
                    <failOnMissingwebxml>false</failOnMissingwebxml>
                </configuration>
            </plugin>

爆红不影响打包

2.重写启动类

@SpringBootApplication
public class DemoApplication  extends SpringBootServletInitializer {
    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }
    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
        return application.sources(DemoApplication.class);
    }
}

注释掉原来的，继承SpringBootServletInitializer类

此时就可以打包了