spring-boot服务启动报: Unable to start embedded container

初次接触spring-boot + spring-cloud构建微服务项目,配置好项目后并选择启动类启动时报如下错误：
[main] ERROR org.springframework.boot.SpringApplication - Application startup failed
org.springframework.context.ApplicationContextException: Unable to start embedded container; nested exception is org.springframework.context.ApplicationContextException: Unable to start EmbeddedWebApplicationContext due to missing EmbeddedServletContainerFactory bean.
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.onRefresh(EmbeddedWebApplicationContext.java:137)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:536)
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:737)
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:370)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:314)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1162)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1151)
    at com.dispatchCenter.main.DispatchCenterApplication.main(DispatchCenterApplication.java:9)
Caused by: org.springframework.context.ApplicationContextException: Unable to start EmbeddedWebApplicationContext due to missing EmbeddedServletContainerFactory bean.
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.getEmbeddedServletContainerFactory(EmbeddedWebApplicationContext.java:189)
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.createEmbeddedServletContainer(EmbeddedWebApplicationContext.java:162)
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.onRefresh(EmbeddedWebApplicationContext.java:134)

    ... 8 common frames omitted

1、根据报错信息发现是在刷新容器的方法onRefresh中抛出的，为什么是刷新容器的方法呢？相信大家都知道spring-boot是基于spring的扩展，是简化spring配置的一个工具，
    至于spring是怎么初始化的在本篇不做概述。我们在这只需要知道EmbeddedWebApplicationContext extends org.springframework.web.context.support.GenericWebApplicationContext。

    下面点进去查看EmbeddedWebApplicationContext此类中刷新容器的方法的源码如下:

	protected void onRefresh() {
        super.onRefresh();  --这里就是刷新spring容器的入口

        try {
            this.createEmbeddedServletContainer();   --捕获的是这个方法中的异常
        } catch (Throwable var2) {
            throw new ApplicationContextException("Unable to start embedded container", var2); --这里捕获异常后抛出
        }
    }

2、接着被捕获异常的方法源码：

private void createEmbeddedServletContainer() {
        EmbeddedServletContainer localContainer = this.embeddedServletContainer;
        ServletContext localServletContext = this.getServletContext();
        if (localContainer == null && localServletContext == null) {
            EmbeddedServletContainerFactory containerFactory = this.getEmbeddedServletContainerFactory();  --根据报错信息这里抛出的异常
            this.embeddedServletContainer = containerFactory.getEmbeddedServletContainer(new ServletContextInitializer[]{this.getSelfInitializer()});
        } else if (localServletContext != null) {
            try {
                this.getSelfInitializer().onStartup(localServletContext);
            } catch (ServletException var4) {
                throw new ApplicationContextException("Cannot initialize servlet context", var4);
            }
        }

        this.initPropertySources();
    }

3、再接着就是抛出异常的根源所在的源码,通过查看源码得出是启动时从beanFactory中找不到所需bean的存在,也就是bean根本没有注册：

protected EmbeddedServletContainerFactory getEmbeddedServletContainerFactory() {
        String[] beanNames = this.getBeanFactory().getBeanNamesForType(EmbeddedServletContainerFactory.class); --这里通过类型去查询bean，结果发现一个都没有就抛出异常了，当然如果超过一个也会抛出异常
        if (beanNames.length == 0) {
            throw new ApplicationContextException("Unable to start EmbeddedWebApplicationContext due to missing EmbeddedServletContainerFactory bean.");
        } else if (beanNames.length > 1) {
            throw new ApplicationContextException("Unable to start EmbeddedWebApplicationContext due to multiple EmbeddedServletContainerFactory beans : " + StringUtils.arrayToCommaDelimitedString(beanNames));
        } else {
            return (EmbeddedServletContainerFactory)this.getBeanFactory().getBean(beanNames[0], EmbeddedServletContainerFactory.class);
        }
    }

4、知道原因了反过去查看代码发现启动类中少写了注解,太粗心大意了

    @EnableEurekaServer
    @SpringBootApplication
    
 5、还有一种情况需要注意，我们使用注解标注了这个启动类，但是还是提示Cannot resolve symbol *等问题，一定要去检查引包是否正确