SpringBoot启动异常 Error starting ApplicationContext.

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2019-05-12 18:44:45.365 ERROR 13480 --- [           main] o.s.b.d.LoggingFailureAnalysisReporter   : 

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APPLICATION FAILED TO START
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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).

出现这个问题的原因是：

spring boot默认会加载org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration类，DataSourceAutoConfiguration类使用了@Configuration注解向spring注入了dataSource bean。因为工程中没有关于dataSource相关的配置信息，当spring创建dataSource bean因缺少相关的信息就会报错。

解决的方法：

加入红色框框的代码.