动态sql

foreach中list是对象时

直接： 对象.属性

<select id="selectStuForeach" resultMap="studentMap">
       select * from student where stu_id in
       <foreach collection="list" item="stu" open="(" close=")" separator=",">
           #{stu.id}
       </foreach>
</select>

PageHelper分页代替limit offset,size

pom.xml:

<!--PageHelper依赖-->
   <dependency>
     <groupId>com.github.pagehelper</groupId>
     <artifactId>pagehelper</artifactId>
     <version>5.2.0</version>
   </dependency>

mybatis.xml:

    <!--pageHelper插件-->
    <plugins>
        <plugin interceptor="com.github.pagehelper.PageInterceptor"></plugin>
    </plugins>

在查询之前分页说明：【startPage(int pageNum, int pageSize)】

 @Test
 public void selectStus() {
     SqlSession sqlSession = MyBatisUtils.getSqlSession();
     StudentDao dao = sqlSession.getMapper(StudentDao.class);
     PageHelper.startPage(1,4);
     List<Student> list = dao.selectStudents();
     sqlSession.close();
     list.forEach(System.out::println);
 }

预留问题：缓存，日志，插件AV21272940