org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is org.apache.commons.dbcp.SQLNestedException: Cannot create PoolableConnectionFactory (Access denied for user ‘root ‘@‘localhost‘ (using password: YES))
### The error may exist in mapper/CustomerMapper.xml
### The error may involve com.zhexiang.mybatis_springmvc.model.selectCustomerByID
### The error occurred while executing a query
### Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is org.apache.commons.dbcp.SQLNestedException: Cannot create PoolableConnectionFactory (Access denied for user ‘root ‘@‘localhost‘ (using password: YES))
	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 com.zhexiang.mybatis_springmvc.dao.impl.CustomerDaoImpl.selectCustomerByID(CustomerDaoImpl.java:18)
	at com.zhexiang.mybatis_springmvc.dao.impl.CustomerDaoImplTest.testSelectCustomerByID(CustomerDaoImplTest.java:37)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at junit.framework.TestCase.runTest(TestCase.java:176)
	at junit.framework.TestCase.runBare(TestCase.java:141)
	at junit.framework.TestResult$1.protect(TestResult.java:122)
	at junit.framework.TestResult.runProtected(TestResult.java:142)
	at junit.framework.TestResult.run(TestResult.java:125)
	at junit.framework.TestCase.run(TestCase.java:129)
	at junit.framework.TestSuite.runTest(TestSuite.java:255)
	at junit.framework.TestSuite.run(TestSuite.java:250)
	at org.junit.internal.runners.JUnit38ClassRunner.run(JUnit38ClassRunner.java:84)
	at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
	at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
Caused by: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is org.apache.commons.dbcp.SQLNestedException: Cannot create PoolableConnectionFactory (Access denied for user ‘root ‘@‘localhost‘ (using password: YES))
	at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:80)
	at org.mybatis.spring.transaction.SpringManagedTransaction.openConnection(SpringManagedTransaction.java:81)
	at org.mybatis.spring.transaction.SpringManagedTransaction.getConnection(SpringManagedTransaction.java:67)
	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)
	... 23 more
Caused by: org.apache.commons.dbcp.SQLNestedException: Cannot create PoolableConnectionFactory (Access denied for user ‘root ‘@‘localhost‘ (using password: YES))
	at org.apache.commons.dbcp.BasicDataSource.createPoolableConnectionFactory(BasicDataSource.java:1549)
	at org.apache.commons.dbcp.BasicDataSource.createDataSource(BasicDataSource.java:1388)
	at org.apache.commons.dbcp.BasicDataSource.getConnection(BasicDataSource.java:1044)
	at org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(DataSourceUtils.java:111)
	at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:77)
	... 33 more
Caused by: java.sql.SQLException: Access denied for user ‘root ‘@‘localhost‘ (using password: YES)
	at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1074)
	at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4120)
	at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4052)
	at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:925)
	at com.mysql.jdbc.MysqlIO.proceedHandshakeWithPluggableAuthentication(MysqlIO.java:1704)
	at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1250)
	at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2465)
	at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2498)
	at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2283)
	at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:822)
	at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
	at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
	at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:404)
	at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:317)
	at org.apache.commons.dbcp.DriverConnectionFactory.createConnection(DriverConnectionFactory.java:38)
	at org.apache.commons.dbcp.PoolableConnectionFactory.makeObject(PoolableConnectionFactory.java:582)
	at org.apache.commons.dbcp.BasicDataSource.validateConnectionFactory(BasicDataSource.java:1556)
	at org.apache.commons.dbcp.BasicDataSource.createPoolableConnectionFactory(BasicDataSource.java:1545)
	... 37 more

出现以上错误原因是：数据源的错误配置：

错误的jdbc.properties

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis?useUnicode=true&characterEncoding=gbk
username=root
password=root

错误的spring配置文件：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

	<!--  config db property file location  -->
	<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
		<property name="locations" value=http://www.mamicode.com/"classpath:jdbc.properties"/>"font-family: Arial, Helvetica, sans-serif;">${username}" />
        <property name="password" value=http://www.mamicode.com/"${password}" />>

正确的jdbc.properties配置：
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mybatis?useUnicode=true&characterEncoding=gbk
jdbc.username=root
jdbc.password=root


Spring4.0.4 官方文档数据源配置：
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context-3.0.xsd">
    
    <!-- Scans within the base package of the application for @Components to configure as beans -->
    <context:component-scan base-package="org.springframework.docs.test" />
    
    <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
        <property name="driverClassName" value=http://www.mamicode.com/"${jdbc.driverClassName}"/>>