Mapper动态代理4大原则

1：mapper.xml的namespace是接口的全包名
2：接口的方法名是mapper下的sql语句的id名
3：接口的参数是mapper下sql语句的paramentType一致
4：接口的返回值与mapper下的sql语句的resultType一致

定义一个mapper.xml

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<?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.mybatis.mapper.userTest">
 <!-- 根据id查询得到一个user对象-->
    <select id="getUser" parameterType="int" 
        resultType="user">
        select * from userinfo where userid=#{id}
    </select>
</mapper>

创建一个接口

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public interface userTest {
//根据id获取用户信息
   public user getUser(int id);
}

在conf.xml中注册mapper

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<mapper resource="com/mybatis/mapping/userTest.xml" />

测试

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@Test
  public void Test1() 
  {
  SqlSession sqlsession=MybatisUtil.getSqlSession();
  userTest mapper= (userTest)sqlsession.getMapper(userTest.class);
  user user= mapper.getUser(1);
  System.out.println(user);
  }