mybatis 使用jdbc.properties文件设置不起作用的解决方法

<?xml version="1.0" encoding="UTF-8" ?> 
<!DOCTYPE configuration 
 PUBLIC "-//mybatis.org//DTD Config 3.0//EN" 
 "http://mybatis.org/dtd/mybatis-3-config.dtd"> 
<configuration> 
 <typeAliases> 
  <typeAlias type="com.hc.entity.UserInfo" alias="UserInfo"/> 
 </typeAliases> 
 <environments default="development"> 
  <environment id="mysql"> 
   <transactionManager type="JDBC"/> 
   <dataSource type="POOLED"> 
    <property name="driver" value="com.mysql.jdbc.Driver"/> 
    <property name="url" value="jdbc:mysql://localhost:3306/db_mybatis"/> 
    <property name="username" value="hhc"/> 
    <property name="password" value="******"/> 
   </dataSource> 
  </environment> 
 </environments> 
 <mappers> 
  <mapper resource="com/hc/mapper/UserInfo.xml"/> 
 </mappers> 
</configuration> 

jdbc.driverClass=com.mysql.jdbc.Driver 
jdbc.url=jdbc:mysql://localhost:3306/db_mybatis 
jdbc.username=hc 
jdbc.password=123456 

<?xml version="1.0" encoding="UTF-8" ?> 
<!DOCTYPE configuration 
 PUBLIC "-//mybatis.org//DTD Config 3.0//EN" 
 "http://mybatis.org/dtd/mybatis-3-config.dtd"> 
<configuration> 
 <properties resource="jdbc.properties"/> 
 <typeAliases> 
  <typeAlias type="com.hc.entity.UserInfo" alias="UserInfo"/> 
 </typeAliases> 
 <environments default="development"> 
  <environment id="mysql"> 
   <transactionManager type="JDBC"></transactionManager> 
   <dataSource type="POOLED"> 
    <property name="driver" value="${jdbc.driverClass}"/> 
    <property name="url" value="${jdbc.url}"/> 
    <property name="username" value="${jdbc.username}"/> 
    <property name="password" value="${jdbc.password}"/> 
   </dataSource> 
  </environment> 
 </environments> 
 <mappers> 
  <mapper resource="com/hc/mapper/userinfo.xml"/> 
 </mappers> 
</configuration>