嘗試了所有評論中的方法，依然連接不上?。?！

1.修改jdbc.properties

jdbc.driver=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/seckill?useUnicode=true&characterEncoding=uft8&serverTimezone=UTC&useSSL=false
jdbc.user=root
jdbc.password=***

同時修改spring-dao.xml；另將超時時間改為0，無限等待

<bean?id="dataSource"?class="com.mchange.v2.c3p0.ComboPooledDataSource">
????<property?name="driverClass"?value="${jdbc.driver}"/>
????<property?name="jdbcUrl"?value="${jdbc.url}"/>
????<property?name="user"?value="${jdbc.user}"/>
????<property?name="password"?value="${jdbc.password}"/>

????<!--?c3p0連接池的私有屬性?-->
????<!--?數(shù)據(jù)庫最大連接對象?默認:15?-->
????<property?name="maxPoolSize"?value="30"/>
????<!--?數(shù)據(jù)庫最小連接對象?默認:3?-->
????<property?name="minPoolSize"?value="10"/>
????<!--?關(guān)閉連接后不自動commit?默認:false?-->
????<property?name="autoCommitOnClose"?value="false"/>
????<!--?獲取連接超時時間?默認:0,表示無限等待-->
????<property?name="checkoutTimeout"?value="0"/>
????<!--?當獲取連接失敗時重試次數(shù)?-->
????<property?name="acquireRetryAttempts"?value="2"/>
</bean>

3.修改pom.xml中各項配置版本

<dependency>
??<groupId>mysql</groupId>
??<artifactId>mysql-connector-java</artifactId>
??<version>8.0.11</version>
??<scope>runtime</scope>
</dependency>
<dependency>
??<groupId>com.mchange</groupId>
??<artifactId>c3p0</artifactId>
??<version>0.9.5.2</version>
</dependency>

依然報錯

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!

### The error may exist in file [F:\seckill\target\classes\mapper\SeckillDao.xml]

### The error may involve org.seckill.dao.SeckillDao.queryById

### The error occurred while executing a query

### 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!

已經(jīng)無力了，求大神解決！?。?/p>