详解mybatis三种分页方式

limit ${startPos},${pageSize}

<if test="startPos!=null and pageSize!=null">
    limit ${startPos},${pageSize}
</if>

<select id="getUserInfo1" parameterType="map" resultType="dayu">
    select * from user
    <if test="startPos!=null and pageSize!=null">
        limit ${startPos},${pageSize}
    </if>
</select>

List<User> getUserInfo1(Map<String,Object> map);

@Test
 public void selectUser() {
     SqlSession session = MybatisUtils.getSession();
     UserMapper mapper = session.getMapper(UserMapper.class);
     //这里塞值
      Map<String,Object> parms = new HashMap<>();
      parms.put("startPos","0");
      parms.put("pageSize","5");
     List<User> users = mapper.getUserInfo1(parms);
     for (User map: users){
         System.out.println(map);
    }
     session.close();
}

@Test
public void selectUserRowBounds() {
    SqlSession session = MybatisUtils.getSession();
    UserMapper mapper = session.getMapper(UserMapper.class);
    // List<User> users = session.selectList("com.dy.mapper.UserMapper.getUserInfoRowBounds",null,new RowBounds(0, 5));
    List<User> users = mapper.getUserInfoRowBounds(new RowBounds(0,5));
    for (User map: users){
        System.out.println(map);
    }
    session.close();
}

List<User> getUserInfoRowBounds(RowBounds rowBounds);

<select id="getUserInfoRowBounds" resultType="dayu">
   select * from user
</select>

<dependency>
   <groupId>com.github.pagehelper</groupId>
   <artifactId>pagehelper</artifactId>
   <version>5.1.7</version>
</dependency>

<plugins>
    <plugin interceptor="com.github.pagehelper.PageInterceptor" />
</plugins>

@Test
public void selectUserPageHelper() {
    SqlSession session = MybatisUtils.getSession();
    UserMapper mapper = session.getMapper(UserMapper.class);
    //第二种，Mapper接口方式的调用，推荐这种使用方式。
    PageHelper.startPage(1, 3);
    List<User> list = mapper.getUserInfo();
    //用PageInfo将包装起来
    PageInfo page = new PageInfo(list);
    for (User map: list){
        System.out.println(map);
    }
    System.out.println("page:---"+page);
    session.close();
}

//第一种，RowBounds方式的调用
List<User> list = sqlSession.selectList("x.y.selectIf", null, new RowBounds(0, 10));
 
//第二种，Mapper接口方式的调用，推荐这种使用方式。
PageHelper.startPage(1, 10);
List<User> list = userMapper.selectIf(1);
 
//第三种，Mapper接口方式的调用，推荐这种使用方式。
PageHelper.offsetPage(1, 10);
List<User> list = userMapper.selectIf(1);
 
//第四种，参数方法调用
//存在以下 Mapper 接口方法，你不需要在 xml 处理后两个参数
public interface CountryMapper {
    List<User> selectByPageNumSize(
            @Param("user") User user,
            @Param("pageNum") int pageNum, 
            @Param("pageSize") int pageSize);
}
//配置supportMethodsArguments=true
//在代码中直接调用：
List<User> list = userMapper.selectByPageNumSize(user, 1, 10);
 
//第五种，参数对象
//如果 pageNum 和 pageSize 存在于 User 对象中，只要参数有值，也会被分页
//有如下 User 对象
public class User {
    //其他fields
    //下面两个参数名和 params 配置的名字一致
    private Integer pageNum;
    private Integer pageSize;
}
//存在以下 Mapper 接口方法，你不需要在 xml 处理后两个参数
public interface CountryMapper {
    List<User> selectByPageNumSize(User user);
}
//当 user 中的 pageNum!= null && pageSize!= null 时，会自动分页
List<User> list = userMapper.selectByPageNumSize(user);
 
//第六种，ISelect 接口方式
//jdk6,7用法，创建接口
Page<User> page = PageHelper.startPage(1, 10).doSelectPage(new ISelect() {
    @Override
    public void doSelect() {
        userMapper.selectGroupBy();
    }
});
//jdk8 lambda用法
Page<User> page = PageHelper.startPage(1, 10).doSelectPage(()-> userMapper.selectGroupBy());
 
//也可以直接返回PageInfo，注意doSelectPageInfo方法和doSelectPage
pageInfo = PageHelper.startPage(1, 10).doSelectPageInfo(new ISelect() {
    @Override
    public void doSelect() {
        userMapper.selectGroupBy();
    }
});
//对应的lambda用法
pageInfo = PageHelper.startPage(1, 10).doSelectPageInfo(() -> userMapper.selectGroupBy());
 
//count查询，返回一个查询语句的count数
long total = PageHelper.count(new ISelect() {
    @Override
    public void doSelect() {
        userMapper.selectLike(user);
    }
});
//lambda
total = PageHelper.count(()->userMapper.selectLike(user));

//获取第1页，10条内容，默认查询总数count
PageHelper.startPage(1, 10);
List<User> list = userMapper.selectAll();
//用PageInfo对结果进行包装
PageInfo page = new PageInfo(list);
//测试PageInfo全部属性
//PageInfo包含了非常全面的分页属性
assertEquals(1, page.getPageNum());
assertEquals(10, page.getPageSize());
assertEquals(1, page.getStartRow());
assertEquals(10, page.getEndRow());
assertEquals(183, page.getTotal());
assertEquals(19, page.getPages());
assertEquals(1, page.getFirstPage());
assertEquals(8, page.getLastPage());
assertEquals(true, page.isFirstPage());
assertEquals(false, page.isLastPage());
assertEquals(false, page.isHasPreviousPage());
assertEquals(true, page.isHasNextPage());