情景
一个 Maven 单模块项目改造为多模块项目后，发现报错：
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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).
Process finished with exit code 1一种可行的解决方案
如果是 Maven 多模块项目，查看 IDEA 右上角 Edit Configurations -> Use classpath of module，此栏应为 包含程序入口的xxxApplication.java 和application.yml的 module：
如上图，博主的程序入口 xxxApplication.java 和application.yml放置于 server 这个 module，brother-takeaway-order是之前单体模块的名称。把此处的 module 切换为server，即可解决报错。