Could not get JDBC Connection

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 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)  

jdbc.properties如下：

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

配置文件：

当出现上面的Exception，而且spring的配置文件如上面两个文件所示时，无法连接数据库的原因在于

这一行因为此时${username}的值并不是jdbc.properties文件中的username值，而是JVM系统环境变量的username。spring容器在管理PropertySource时，不光读取自己写的properties文件，spring也会把JVM system properties和JVM system env properties都读取到容器中，所以请不要使用和JVM properties相同的key。