关于idea中SpringBoot启动失败的坑

很多时候你新建了Maven 或者SpringBoot 工程，激动的点了主启动类，你就发现了下面的错误

 Error starting Tomcat context. Exception: org.springframework.beans.factory.BeanCreationException. Message: 
Error creating bean with name 'servletEndpointRegistrar' defined in class path resource 
[org/springframework/boot/actuate/autoconfigure/endpoint/web/ServletEndpointManagementContextConfiguration$
WebMvcServletEndpointManagementContextConfiguration.class]: 
Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: 
Failed to instantiate [org.springframework.boot.actuate.endpoint.web.ServletEndpointRegistrar]: 
Factory method 'servletEndpointRegistrar' threw exception; 
nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: 
Error creating bean with name 'healthEndpoint' defined in class path resource 
[org/springframework/boot/actuate/autoconfigure/health/HealthEndpointConfiguration.class]: 
Unsatisfied dependency expressed through method 'healthEndpoint' parameter 0; 
nested exception is org.springframework.beans.factory.BeanCreationException: 
Error creating bean with name 'healthContributorRegistry' defined in class path resource 
[org/springframework/boot/actuate/autoconfigure/health/HealthEndpointConfiguration.class]: 
Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: 
Failed to instantiate [org.springframework.boot.actuate.health.HealthContributorRegistry]: 
Factory method 'healthContributorRegistry' threw exception; 
nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: 
Error creating bean with name 'org.springframework.boot.actuate.autoconfigure.jdbc.DataSourceHealthContributorAutoConfiguration': 
Unsatisfied dependency expressed through constructor parameter 0;
 nested exception is org.springframework.beans.factory.BeanCreationException: 
Error creating bean with name 'dataSource' defined in class path resource [org/springframework/boot/autoconfigure/jdbc/DataSourceConfiguration$Hikari.class]: 
Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.zaxxer.hikari.HikariDataSource]: 
Factory method 'dataSource' threw exception; nested exception is org.springframework.boot.autoconfigure.jdbc.DataSourceProperties$DataSourceBeanCreationException: 
Failed to determine a suitable driver class
[  restartedMain] o.apache.catalina.core.StandardService   : Stopping service [Tomcat]
 --- [  restartedMain] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: 
org.springframework.context.ApplicationContextException: Unable to start web server; nested exception is org.springframework.boot.web.server.WebServerException: 
Unable to start embedded Tomcat
 --- [  restartedMain] ConditionEvaluationReportLoggingListener : 

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2020-09-03 13:12:04.338 ERROR 24572 --- [  restartedMain] o.s.b.d.LoggingFailureAnalysisReporter   : 

***************************
APPLICATION FAILED TO START
***************************

Description:

Failed to configure a DataSource: 'url' attribute is not specified and no embedded datasource could be configured.

Reason: Failed to determine a suitable driver class

Action:

Consider the following:
	If you want an embedded database (H2, HSQL or Derby), please put it on the classpath.
	If you have database settings to be loaded from a particular profile you may need to activate it (no profiles are currently active).

　　这里说的是啥意思呢，你没有数据库相关的链接，数据库相关的链接在哪里配置呢，就是在你的Resource文件目录下的properties 或者yml文件中

但是这里你可能会说，我**不用数据库，我干啥配这个b玩意，我想说这句话的时候，你已经点了很多遍的主启动都报这个错误，

今天你算来对了，我敢肯定80%的人都遇到过这个问题。但是不知道为啥，今天我给你分析一下昂：

①：在IDEA 中用SpringInitial  点点点生成的SpringBoot/cloud项目
②：跟视频操作，一顿操作后发现不能启动，
③：DonwLoad下的代码   复制进去的POM依赖

还有很多昂，不墨迹了说重点吧。
解决方法：

首先着重看自己的POM依赖（是自己的POM，不是父工程，也不是其他工程，是自己的）中有无以下依赖

<dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>${mysql.version}</version>
</dependency>

　　

<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>

　　经过鄙人的测试，就是第一个依赖捣的鬼，这就是为啥你加了这个依赖你不配置相关的mysql链接，Spring就给你报错的原因。

最后提醒：按需注入POM才是正道，老铁们，我做的对么？