c3p0连接池连接mysql因版本异常 com.mchange.v2.resourcepool.TimeoutException

最近复习数据库连接池遇到mysql版本导致连接异常问题记录如下

环境：mysql版本：mysql8.0.25

        jar包版本：

        mysql驱动包：mysql-connector-java-8.0.11.jar

        c3p0连接池jar包：mchange-commons-java-0.2.12.jar  mysql-connector-java-8.0.11.jar

出现异常：

Exception in thread "main" java.sql.SQLException: An attempt by a client to checkout a Connection has timed out.
    at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:118)
    at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:77)
    at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:690)
    at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:140)
    at myStudy_jdbc.com.xiaoqiang.JDBCConnectionPool.c3p0DempMethod(JDBCConnectionPool.java:52)
    at myStudy_jdbc.com.xiaoqiang.JDBCConnectionPool.main(JDBCConnectionPool.java:45)
Caused by: com.mchange.v2.resourcepool.TimeoutException: A client timed out while waiting to acquire a resource from com.mchange.v2.resourcepool.BasicResourcePool@18e8568 -- timeout at awaitAvailable()
    at com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable(BasicResourcePool.java:1467)
    at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:644)
    at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:554)
    at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutAndMarkConnectionInUse(C3P0PooledConnectionPool.java:758)
    at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:685)
    ... 3 more

解决方案：

        修改连接配置，8.0驱动之前驱动类的位置是 com.mysql.jdbc.Driver，8.0版本之后驱动类的位置是com.mysql.cj.jdbc.Driver，8.0版本的url连接需要加上使用的时区。

配置修改如下：

<c3p0-config>
  <!-- 使用默认的配置读取连接池对象 -->
  <default-config>
  	<!--  连接参数 -->
  	<!-- mysql 8.0版本配置 -->
    <property name="driverClass">com.mysql.cj.jdbc.Driver</property>
    <property name="jdbcUrl">jdbc:mysql://127.0.0.1:3306/db1?serverTimezone=UTC</property>
    <!-- mysql 8.0版本之前配置 -->
    <!--  
    	<property name="driverClass">com.mysql.jdbc.Driver</property>
    	<property name="jdbcUrl">jdbc:mysql://127.0.0.1:3306/db1</property> 
    -->
    
    <property name="user">root</property>
    <property name="password">Xiaoqiang1006</property>
    
    <!-- 连接池参数 -->
    <!--初始化的申请的连接数量-->
    <property name="initialPoolSize">5</property>
    <!--最大的连接数量-->
    <property name="maxPoolSize">10</property>
    <!--连接超时时间-->
    <property name="checkoutTimeout">3000</property>
  </default-config>

  <named-config name="otherc3p0"> 
    <!--  连接参数 -->
    	<!-- mysql 8.0版本配置 -->
    <property name="driverClass">com.mysql.cj.jdbc.Driver</property>
    <property name="jdbcUrl">jdbc:mysql://127.0.0.1:3306/db1?serverTimezone=UTC</property>
    <!-- mysql 8.0版本之前配置 -->
    <!--  
    	<property name="driverClass">com.mysql.jdbc.Driver</property>
    	<property name="jdbcUrl">jdbc:mysql://127.0.0.1:3306/db1</property> 
    -->

    <property name="user">root</property>
    <property name="password">Xiaoqiang1006</property>
    
    <!-- 连接池参数 -->
    <property name="initialPoolSize">5</property>
    <property name="maxPoolSize">8</property>
    <property name="checkoutTimeout">1000</property>
  </named-config>
</c3p0-config>