警告: com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@26b43cc8 -- Acquisition Attempt Failed!!! Clearing pending acquires. While trying to acquire a needed new resource, we failed to succeed more than the maximum number of allowed acquisition attempts (2). Last acquisition attempt exception:
java.sql.SQLException: Unknown system variable 'query_cache_size'
七月 31, 2019 10:56:47 下午 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask run
警告: com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@441cffbf -- Acquisition Attempt Failed!!! Clearing pending acquires. While trying to acquire a needed new resource, we failed to succeed more than the maximum number of allowed acquisition attempts (2). Last acquisition attempt exception:
java.sql.SQLException: Unknown system variable 'query_cache_size'
七月 31, 2019 10:56:47 下午 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask run
警告: com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@32a79625 -- Acquisition Attempt Failed!!! Clearing pending acquires. While trying to acquire a needed new resource, we failed to succeed more than the maximum number of allowed acquisition attempts (2). Last acquisition attempt exception:
java.sql.SQLException: Unknown system variable 'query_cache_size'
org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.PersistenceException:
### Error querying database. Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is java.sql.SQLException: Connections could not be acquired from the underlying database!
### The error may exist in file [code\o2o\target\classes\mapper\AreaDao.xml]
### The error may involve com.imooc.o2o.dao.AreaDao.queryArea
### The error occurred while executing a query
### Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is java.sql.SQLException: Connections could not be acquired from the underlying database!
Caused by: org.apache.ibatis.exceptions.PersistenceException:
### Error querying database. Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is java.sql.SQLException: Connections could not be acquired from the underlying database!
### The error may exist in file [code\o2o\target\classes\mapper\AreaDao.xml]
### The error may involve com.imooc.o2o.dao.AreaDao.queryArea
### The error occurred while executing a query
### Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is java.sql.SQLException: Connections could not be acquired from the underlying database!
今天遇到这个问题，昨天还能运行的今天就出错了，查了网上的资料，把
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.37 </version>
<scope>runtime</scope>
</dependency>改成
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.47 </version>
<scope>runtime</scope>
</dependency>也就是把对应的mysql-connector-java版本从5.1.37改成5.1.47就解决了
参考：https://blog.csdn.net/xx345385463/article/details/90696133