JavaWeb开发：java.lang.ClassNotFoundException: com.mysql.jdbc.Driver

最新推荐文章于 2022-03-13 11:48:59 发布

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最新推荐文章于 2022-03-13 11:48:59 发布

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本文详细解析了在使用c3p0连接池时遇到的java.lang.ClassNotFoundException异常，即MySQL驱动未找到的问题。通过逐步排查，最终定位到未正确导入mysql-connector-java-5.0.8-bin.jar这一根本原因。

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报错信息：

 java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
	at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1309)
	at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1138)
	at java.lang.Class.forName0(Native Method)
	at java.lang.Class.forName(Class.java:264)
	at com.mchange.v2.c3p0.DriverManagerDataSource.ensureDriverLoaded(DriverManagerDataSource.java:100)
	at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:132)
	at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:182)
	at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:171)
	at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137)
	at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014)
	at com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32)
	at com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1810)
	at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)

首先观察到第一行：java.lang.ClassNotFoundException: com.mysql.jdbc.Driver，是MySQL的驱动没有找到
- 在断点调试之后发现Servlet、Service、Dao层都能正常运行，直到return qr.query(sql, new BeanHandler<>(User.class),username);
- 所以应该是数据库连接的问题，最后发现是因为没有导入MySql的jar包…mysql-connector-java-5.0.8-bin.jar.