SSM实现分页查询

前言

分页基本上是我们项目中所必须的功能，当数据量过大时，可能会导致各种各样的问题发生，例如：服务器资源被耗尽，因数据传输量过大而使处理超时，等等。最终都会导致查询无法完成。解决这个问题的一个策略就是“分页查询”，也就是说不要一次性查询所有的数据，每次只查询一“页“的数据。这样分批次地进行处理，可以呈现出很好的用户体验，对服务器资源的消耗也不大。本文主要是使用limit来实现分页的查询。

 实现

1、分页工具类

package com.inchlifc.util;

import java.util.List;

/**
 * @author 小小渔夫
 * @description 分页实体类
 */
public class PageBean<T> {

    private int currPage;//当前页数
    private int pageSize;//每页显示的记录数
    private int totalCount;//总记录数
    private int totalPage;//总页数
    private List<T> lists;//每页的显示的数据

    public PageBean() {
        super();
    }

    public int getCurrPage() {
        return currPage;
    }

    public void setCurrPage(int currPage) {
        this.currPage = currPage;
    }

    public int getPageSize() {
        return pageSize;
    }

    public void setPageSize(int pageSize) {
        this.pageSize = pageSize;
    }

    public int getTotalCount() {
        return totalCount;
    }

    public void setTotalCount(int totalCount) {
        this.totalCount = totalCount;
    }

    public int getTotalPage() {
        return totalPage;
    }

    public void setTotalPage(int totalPage) {
        this.totalPage = totalPage;
    }

    public List<T> getLists() {
        return lists;
    }

    public void setLists(List<T> lists) {
        this.lists = lists;
    }

}

2、mapper层

 <select id="selectInStockList" resultType="com.inchlifc.entity.InStock">
      SELECT * FROM in_stock ORDER BY createTime desc
      <if test="pageStart!=null and pageSize!=null">
          limit #{pageStart},#{pageSize}
      </if>
</select>

3、Dao层

/**
* 分页查询所有信息
*
* @param pageStart 页数
* @param pageSize  每页显示条数
* @return
*/
List<InStock> selectInStockList(@Param("pageStart") int pageStart, @Param("pageSize") int pageSize);

4、service层

/**
* 分页查询所有信息
*
* @return
*/
public PageBean<InStock> findAllInStock(int pageStart) {
    PageBean<InStock> pageBean = new PageBean<InStock>();
    pageBean.setCurrPage(pageStart);

    pageBean.setPageSize(10);

    //封装总记录数
    int totalCount = inStockDao.inStockCountAll();
    pageBean.setTotalCount(totalCount);

    //封装总页数
    double tc = totalCount;
    Double num = Math.ceil(tc / 10);//向上取整
    pageBean.setTotalPage(num.intValue());

    //封装每页显示的数据
    List<InStock> lists = inStockDao.selectInStockList((pageStart - 1) * 10, 10);
    pageBean.setLists(lists);
    return pageBean;
}

5、controller层

/**
* 分页查询所有信息
* @param currentPage 当前页数
* @param model model
* @param session 会话
* @return
*/
@RequestMapping(value = "/list", method = RequestMethod.GET)
@ResponseBody
private ModelAndView getInStockList(@RequestParam(value = "currentPage", defaultValue = "1", required = false) int currentPage, Model model, HttpSession session) {
    ModelAndView mv = new ModelAndView();
    //获取当前登录用户名
    String currentUserName = (String) session.getAttribute("userName");
    if (!currentUserName.equals("engine")) {
        mv.setViewName("permission");
        return mv;
    }
    mv.addObject("stockList", inStockService.findAllInStock(currentPage));
    mv.setViewName("inStockList");
    return mv;
}

6、显示页面

<ul style="font-size: large;text-align: center">
        <span>第${requestScope.stockList.currPage }/ ${requestScope.stockList.totalPage}页</span>
        <span>总记录数：${requestScope.stockList.totalCount }  每页显示:${requestScope.stockList.pageSize}</span>
        <span>
            <c:if test="${requestScope.stockList.currPage != 1}">
                <a href="<%=basePath%>inStock/list?currentPage=1">[首页]</a>
                <a href="<%=basePath%>inStock/list?currentPage=${requestScope.stockList.currPage-1}">[上一页]</a>
            </c:if>

            <c:if test="${requestScope.stockList.currPage != requestScope.stockList.totalPage}">
                <a href="<%=basePath%>inStock/list?currentPage=${requestScope.stockList.currPage+1}">[下一页]</a>
                <a href="<%=basePath%>inStock/list?currentPage=${requestScope.stockList.totalPage}">[尾页]</a>
            </c:if>
        </span>
</ul>

7、结果显示