在刚刚开始搭建Mybatis源码解析，一步一步从浅入深 简单示例的时候，我使用的是mysql 5.1.12版本的驱动包。运行时出现如下错误：
Cause: java.sql.SQLException: Error setting driver on UnpooledDataSource. Cause: java.lang.ClassNotFoundException: Cannot find class: com.mysql.jdbc.Driver
org.apache.ibatis.exceptions.PersistenceException: ### Error querying database. Cause: java.sql.SQLException: Error setting driver on UnpooledDataSource. Cause: java.lang.ClassNotFoundException: Cannot find class: com.mysql.jdbc.Driver ### The error may exist in mapper/userDao-mapping.xml ### The error may involve com.zcz.learnmybatis.dao.UserDao.findUserById ### The error occurred while executing a query ### Cause: java.sql.SQLException: Error setting driver on UnpooledDataSource. Cause: java.lang.ClassNotFoundException: Cannot find class: com.mysql.jdbc.Driver at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:26) at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:111) at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:102) at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:66) at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:68) at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:52) at com.sun.proxy.$Proxy2.findUserById(Unknown Source) at com.zcz.test.UserDaoTest.finUserById(UserDaoTest.java:20) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:497) at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44) at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50) at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236) at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229) at org.junit.runners.ParentRunner.run(ParentRunner.java:309) at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86) at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:538) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:760) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:460) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:206) Caused by: java.sql.SQLException: Error setting driver on UnpooledDataSource. Cause: java.lang.ClassNotFoundException: Cannot find class: com.mysql.jdbc.Driver at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.initializeDriver(UnpooledDataSource.java:215) at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.doGetConnection(UnpooledDataSource.java:194) at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.doGetConnection(UnpooledDataSource.java:190) at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.getConnection(UnpooledDataSource.java:92) at org.apache.ibatis.datasource.pooled.PooledDataSource.popConnection(PooledDataSource.java:375) at org.apache.ibatis.datasource.pooled.PooledDataSource.getConnection(PooledDataSource.java:84) at org.apache.ibatis.transaction.jdbc.JdbcTransaction.openConnection(JdbcTransaction.java:134) at org.apache.ibatis.transaction.jdbc.JdbcTransaction.getConnection(JdbcTransaction.java:61) at org.apache.ibatis.executor.BaseExecutor.getConnection(BaseExecutor.java:279) at org.apache.ibatis.executor.SimpleExecutor.prepareStatement(SimpleExecutor.java:72) at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:59) at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:267) at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:137) at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:96) at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:77) at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:108) ... 29 more
具体原因未知，我会继续跟踪，如果有看到的大神请留言指导。
解决办法，将5.1.12版本的mysql驱动包更换成5.1.44版本。问题解决；
原创不易，转载请声明出处：https://www.cnblogs.com/zhangchengzi/p/9672070.html