A problem was found in the use of the latest version of SpringBoot 2.4.2 in the project of learning the grain mall in Silicon Valley
When importing Renren's open source renren -fast project, the connection to the database has been failed, showing that the connection timed out or the number of connections and other problems.
After trying to resolve the unsuccessful, I plan to reload the maven dependency.
maven-->clean-->After finding the warning message, change the pom.xml file of the renren-fast project
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.4.2</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>After changing to my own version, a new problem appeared that javax.validation.constraints did not exist
Finally through Baidu
https://blog.csdn.net/qq_43012792/article/details/108919426
After the above article found related problems.
Can be tested successfully