springboot开发环境低引起的依赖冲突问题
在我初学springboot的时候，碰到了一个深坑，记录下过程。
开发环境:eclipse4.6
刚在springboot官网上下载并导入一个springboot项目，就发现pom.xml文件报错，为了解决后续隐藏的麻烦（主观上看着也不爽），于是查到了原因：初步确定是Eclipse中自带的Maven插件版本太低的原因（我用的Eclipse是Eclipse Neon (4.6)版本，自带Maven插件），需要更新Maven插件。
解决办法:https://www.cnblogs.com/wanggangblog/p/8901516.html
终于不报错了，于是试试能否启动成功，结果又出现，SpringBoot应用部署到Tomcat中无法启动问题：
解决办法:https://www.cnblogs.com/a8457013/p/7687764.html
这里我只修改了tomcat版本，后续依赖并没有添加，于是又出现了:
org.springframework.context.ApplicationContextException: Unable to start web server; nested exception is org.springframework.context.ApplicationContextException: Unable to start ServletWebServerApplicationContext due to missing ServletWebServerFactory bean.
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.onRefresh(ServletWebServerApplicationContext.java:157) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:543) ~[spring-context-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:142) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:775) [spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) [spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:316) [spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1260) [spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1248) [spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
at cn.tedu.springboot.DemoApplication.main(DemoApplication.java:12) [classes/:na]
Caused by: org.springframework.context.ApplicationContextException: Unable to start ServletWebServerApplicationContext due to missing ServletWebServerFactory bean.
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.getWebServerFactory(ServletWebServerApplicationContext.java:206) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.createWebServer(ServletWebServerApplicationContext.java:180) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.onRefresh(ServletWebServerApplicationContext.java:154) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
... 8 common frames omitted
后来把后面的