1、在用Mybatis时要先导入jar包

<dependency>
  <groupId>org.mybatis</groupId>
  <artifactId>mybatis</artifactId>
  <version>x.x.x</version>
</dependency>

2、学习会了配置Mybatis的核心配置文件

在Mybatis的核心配置文件中可以配置一些? 日志??、mapper.xml 、类型别名（typeAliases） 、缓存等

?

?3、用注解简化一些简单的CURD

public interface TeacherMapper{

  @select("select * from teacher" wahere id = #{tid})
  Teacher getTacher(@param("tid")int id);


}

?相对的就要在核心配置文件中绑定

<mappers>
    
   <mapper class = "com.peng.dao.TeacherMapper"/>

</mappers>

4、动态 SQL

动态SQL的功能标签：if、trim (where, set)、foreach

? if标签：如果name不等于空就会拼接里面的SQL

<select>
   select * from teacher
   <if test = "name != null">
    where name = #{name}
   </if>
</select>

? where：它可以很智能的把一些多余的and去掉

<select>
   select * from teacher
   <where>
      <if test = "id != null">
         id = #{id}
      </if>
      <if test = "name != null">
         and name = #{name}
      </if>
   </where>
</select>

set标签:它可以把你多加的，去除

<update>
   update teacher 
   <set>
      <if test = "password != null">
         password = #{password},
      </if>
      <if test = "name != null">
         name = #{name}
      </if>
   </set>
   where id = #{id}
</update>

foreach标签:它可以遍历一些合集比如拼接这样的SQL：select * from 表名 where (id=? or id=?)

public interface StudentMapper {
     //用动态SQL查询id=（1，2）的学生
    List<Student> queryStudent(Map map);
}

     <!--         调用的方法             传入的参数            返回的参数类型             -->
     <select id="queryStudent" parameterType="map" resultType="com.peng.pojo.Student">
         select * from student
         <where>
             <!--   要遍历的集合名    遍历后每个参数的名字  开始     分割符        结束-->
             <foreach collection="ids" item="id" open=" (" separator="or" close=")">
                 id=#{id}
             </foreach>
         </where>
     </select>

 @Test
    public void w2(){

        SqlSession sqlSession = MybatisUtil.getSqlSession();
        StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);

        ArrayList<Integer> list = new ArrayList<>();
        HashMap hashMap = new HashMap();
        list.add(1);
        list.add(2);
        hashMap.put("ids",list);


        List<Student> students = mapper.queryStudent(hashMap);
        for (Student student : students) {
            System.out.println(student);
        }

        sqlSession.close();

    }