configuration.xml里：

    1. <?xml version="1.0" encoding="UTF-8" ?>
    2. <!DOCTYPE configuration
    3.         PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
    4.         "http://mybatis.org/dtd/mybatis-3-config.dtd">
    5. <configuration>
    6.     <environments default="development">
    7.         <environment id="development">
    8.             <transactionManager type="JDBC"/>
    9.             <dataSource type="POOLED">
    10.                 <property name="driver" value="com.mysql.jdbc.Driver"/>
    11.                 <property name="url" value="jdbc:mysql://localhost:3306/testmybatis?useSSL=false"/>
    12.                 <property name="username" value="root"/>
    13.                 <property name="password" value="root"/>
    14.             </dataSource>
    15.         </environment>
    16.     </environments>
    17.     <mappers>
    18.         <mapper class="dao.StudentDao"/>
    19.     </mappers>
    20. </configuration>

    原来的标签下的mapper里是resource，

    1.     <mappers>
    2.         <mapper resource="studentMapper.xml"/>
    3.     </mappers>

    基于注解的话，标签就改成了class

    1.     <mappers>
    2.         <mapper class="dao.StudentDao"/>
    3.     </mappers>

    如果没改过来，会报错：
    image.png