MyBatis 账号密码正确 连接数据库仍出现Access denied问题

问题描述及解决方案

在写一个MyBatis从数据库中读取数据的示例程序时，总是出现如下报错信息：

Exception in thread "main" org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: java.sql.SQLException: Access denied for user 'root'@'localhost' (using password: YES)
### The error may exist in org/example/dao/StudentDao.xml
### The error may involve org.example.dao.StudentDao.selectStudents
### The error occurred while executing a query
### Cause: java.sql.SQLException: Access denied for user 'root'@'localhost' (using password: YES)
	at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:153)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:145)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:140)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:135)
	at org.example.MyApp.main(MyApp.java:29)
Caused by: java.sql.SQLException: Access denied for user 'root'@'localhost' (using password: YES)
	at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1055)
	at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956)
	at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3558)
	at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3490)
	at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:919)
	at com.mysql.jdbc.MysqlIO.secureAuth411(MysqlIO.java:3996)
	at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1284)
	at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2137)
	at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:776)
	at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:46)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
	at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
	at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:352)
	at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:284)
	at java.sql.DriverManager.getConnection(DriverManager.java:664)
	at java.sql.DriverManager.getConnection(DriverManager.java:208)
	at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.doGetConnection(UnpooledDataSource.java:224)
	at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.doGetConnection(UnpooledDataSource.java:219)
	at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.getConnection(UnpooledDataSource.java:95)
	at org.apache.ibatis.datasource.pooled.PooledDataSource.popConnection(PooledDataSource.java:432)
	at org.apache.ibatis.datasource.pooled.PooledDataSource.getConnection(PooledDataSource.java:89)
	at org.apache.ibatis.transaction.jdbc.JdbcTransaction.openConnection(JdbcTransaction.java:139)
	at org.apache.ibatis.transaction.jdbc.JdbcTransaction.getConnection(JdbcTransaction.java:61)
	at org.apache.ibatis.executor.BaseExecutor.getConnection(BaseExecutor.java:337)
	at org.apache.ibatis.executor.SimpleExecutor.prepareStatement(SimpleExecutor.java:86)
	at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:62)
	at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:325)
	at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:156)
	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:109)
	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:89)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:151)
	... 4 more

Process finished with exit code 1

此时数据库的主配置文件中，dataSource 标签的内容如下：

<dataSource type="POOLED">
    <property name="driver" value="com.mysql.jdbc.Driver"/>
    <property name="url" value="jdbc:mysql://localhost:3307/mybatis_test"/>
    <property name="username" value="root"/>
    <property name="password" value="123"/>
</dataSource>

Access denied for user 'root'@'localhost'，也就是拒绝访问，但我在配置文件中写的username和password都是正确的，花了一两的小时试图找出问题所在，但无果。

我访问的数据库是MariaDB，而且我的电脑上装了两个数据库，一个是MySQL，在3306端口上，另一个则是MariaDB，在3307端口上。MySQL数据库的账号密码分别是root和password（没错，就是密码的英文），MariaDB的账号密码分别为root和123。

之前学JDBC时，写com.mysql.jdbc.Driver和jdbc:mysql://localhost:3307/数据库名是可以正常访问MariaDB中的数据的。因为之前知道MariaDB的底层其实和MySQL很相似，于是就以为MariaDB和MySQL的访问没什么区别。

但是现在这套用在MyBatis上却不行了。后来想到会不会是MariaDB和MySQL所要用的依赖不同？后来一查还真是，于是把依赖改成MariaDB的，如下：

<!--mariadb依赖-->
<dependency>
    <groupId>org.mariadb.jdbc</groupId>
    <artifactId>mariadb-java-client</artifactId>
    <version>2.7.3</version>
</dependency>

并且将dataSource标签中的driver标签和url标签改成MariaDB的：

<dataSource type="POOLED">
    <property name="driver" value="org.mariadb.jdbc.Driver"/>
    <property name="url" value="jdbc:mariadb://localhost:3307/mybatis_test"/>
    <property name="username" value="root"/>
    <property name="password" value="123"/>
</dataSource>

于是就可以正常访问MariaDB数据库了。

总结

所以为什么会报Access denied的错误呢？

是因为MyBatis以为我要访问的是MySQL数据库，但是MySQL的账号密码不对，于是出现拒绝访问的错误。于是修改配置，指定要访问MariaDB数据库，问题就解决了。