2024/1/18日 日志 关于Vue && Element 的后续---》综合案例（6）

功能4：分页查询

BrandMapper

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/**
 * 分页查询
 * @param begin
 * @param size
 * @return
 */
@Select("select * from tb_brand limit #{begin} , #{size}")
@ResultMap("brandResultMap")
List<Brand> selectByPage(@Param("begin") int begin,@Param("size") int size);

/**
 * 查询总记录数
 * @return
 */
@Select("select count(*) from tb_brand ")
int selectTotalCount();

BrandServiceImpl

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@Override
public PageBean<Brand> selectByPage(int currentPage, int pageSize) {
    //2. 获取SqlSession对象
    SqlSession sqlSession = factory.openSession();
    //3. 获取BrandMapper
    BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);

    //4. 计算开始索引
    int begin = (currentPage - 1) * pageSize;
    // 计算查询条目数
    int size = pageSize;

    //5. 查询当前页数据
    List<Brand> rows = mapper.selectByPage(begin, size);

    //6. 查询总记录数
    int totalCount = mapper.selectTotalCount();

    //7. 封装PageBean对象
    PageBean<Brand> pageBean = new PageBean<>();
    pageBean.setRows(rows);
    pageBean.setTotalCount(totalCount);

    //8. 释放资源
    sqlSession.close();

    return pageBean;
}

BrandServlet

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public void selectByPage(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    //1. 接收 当前页码 和 每页展示条数    url?currentPage=1&pageSize=5
    String _currentPage = request.getParameter("currentPage");
    String _pageSize = request.getParameter("pageSize");

    int currentPage = Integer.parseInt(_currentPage);
    int pageSize = Integer.parseInt(_pageSize);

    //2. 调用service查询
    PageBean<Brand> pageBean = brandService.selectByPage(currentPage, pageSize);

    //2. 转为JSON
    String jsonString = JSON.toJSONString(pageBean);
    //3. 写数据
    response.setContentType("text/json;charset=utf-8");
    response.getWriter().write(jsonString);
}