SSM实现分页查询

墨蓝 2023-06-28 08:41 4阅读 0赞

## 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 ###

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2N4MjQzNjk4_size_16_color_FFFFFF_t_70][]

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