Springboot startup error failed to configure a datasource

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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

This error is always reported when springboot starts
my solution:
1. Check whether the Resources folder is configured. Mine was gray before, and it is equipped with



2. Use Maven clean

and start successfully.

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