[Java知识库]记：Failed to obtain JDBC Connection； nested exception is java.sql.SQLException: Connections could not

数据库版本：8.0.x

搭建ssm项目时遇到的问题,使用的是Spring+Mybatis+c3po 学习搭建框架。

遇到：

org.mybatis.spring.MyBatisSystemException: nested exception is
org.apache.ibatis.exceptions.PersistenceException:

Error querying database. Cause:
org.springframework.jdbc.CannotGetJdbcConnectionException: Failed to
obtain JDBC Connection; nested exception is java.sql.SQLException:
Connections could not be acquired from the underlying database!

网上搜了终于找到了答案并成功解决，再次总结并希望能帮到遇到同样问题的朋友：

1.引用外部库 mysql-connector-java-8.0.26

<dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.26</version>
        </dependency>

2. 引入最新版的c3p0

<!-- https://mvnrepository.com/artifact/com.mchange/c3p0 -->
<dependency>
    <groupId>com.mchange</groupId>
    <artifactId>c3p0</artifactId>
    <version>0.9.5.5</version>
</dependency>

3.连接的驱动地址为"com.mysql.cj.jdbc.Driver"
Mysql和mysql-connector都为8.0以上的版本时，连接驱动就不要再用：com.mysql.jdbc.Driver了，要引用com.mysql.cj.jdbc.Driver

4.建立连接时url的一些参数

url加上：useJDBCCompliantTimezoneShift=true&serverTimezone=UTC

jdbc.url=jdbc:mysql://localhost:3306/ssmbuild?
useUnicode=true&useJDBCCompliantTimezoneShift=true&serverTimezone=UTC&characterEncoding=utf8

到此，我的问题已经解决。