MyBatis第一天配置文件

1. 在src文件夹下新建MyBatis.xml文件

<?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>
   <environments default="mysql">
       <environment id="mysql">
         <transactionManager type="JDBC"></transactionManager>
           <dataSource type="POOLED">
              <property name="driver" value="com.mysql.jdbc.Driver"/>
              <property name="url" value="jdbc:mysql://localhost:3306/test"/>
              <property name="username" value="root"/>
              <property name="password" value="root"/>
           </dataSource>
       </environment>
   </environments>
   <mappers>
      <mapper  resource="com/lhf/mapper/UserMapper.xml"/>
   </mappers>
</configuration>

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2. 新建以 mapper 结尾的包,在包下新建:实体类名+Mapper.xml
   2.1 文件作用:编写需要执行的 SQL 命令
   2.2 把 xml 文件理解成实现类.
   2.3xml 文件内容

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.lhf.mapper.UserMapper">
      <!-- id:方法名 parameterType:定义参数类型 resultType:返回值类型.
                               如果方法返回值是 list,在 resultType 中写 List 的泛型, 因为 mybatis 对 jdbc 封装,一行一行读取数据 --> 
    <select id="selectAll" resultType="com.lhf.pojo.User">
       select * from t_user
    </select>
    <select id="selectMap" resultType="com.lhf.pojo.User">
       select * from t_user
    </select>
</mapper>