【Mybatis 框架（自学）】Day05--2022/3/13

分页

为什么要分页

• 为了减少数据的处理量，所以采用分页功能

使用Limit分页

SELECT * FROM 表明 limit startIndex,pageSize;

//接口实现类定义分页查询方法
public interface StudentMapper{
    
    List<Student> selectStudentByLimit(Map<String,Object> map);
    
}

<!--Mapper映射-->
<select id="selectStudentByLimit" parameterType="map" resultType="Student">
	select * from tbstudent limit #{startIndex},#{pageSize}
</select>

//Junit测试
@Test
public void selectStudentByLimit(){
    SqlSession sqlSession = MybatisUtils.getConnection();
    StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
    
    try{
        Map<String,Object> map = new HashMap<>();
        map.put("startIndex",0);
        map.put("pageSize",3)
        List<Student> studentList = studentMapper.selectStudentByLimit(map);
        for(Student student:studentList){
            sout(student);
        }
    }catch(Exception e){
        e.prinStackTrace();
    }finally{
        closeSqlSession(sqlSession)
    }
}

RowBounds分页

select * from 表明 (因为此查询操作直接面向对象来生成，不再使用Sql实现分页)

//接口实现类
public interface StudentMapper{
    
    List<Student> selectStudentByRowBoudns();
    
}

<!--Mapper映射-->
<select id="selectStudentByRowBoudns" resultType="Student">
		select * from 表明
</select>

//Junit测试
public void selectStudentByRowBoudns(){
    //导入工具类
    MybatisUtils mybatisUtils = new MybatisUtils();
    //建立sqlSession
    SqlSession sqlSession = mybatisUtils.getConnection();
    //新建接口实现类对象
    StudentMapper studnetMapper = sqlSession.getMapper(StudentMapper.class);
    
    try{
        //重点：通过对象实现分页
        RowBoudns rowBoudns = new RowBounds(1,3)//从第一个开始到第三个结束
        
        List<Student> studentList = sqlSession.selectList("com.xxxx.方法					名",null,rowBoudns);
        /*
        	关于opensession自带sql语句的参数
			selectList("方法名",Object,RowBounds);        
        */
        studentList.for
            sout(student);
        
    }catch(Exception e){
        e.printStackTrace();
    }finally{
        closeSqlSession(sqlSession);
    }
     
}