Servlet实现后台分页查询
相信大家在搭建后台的时候，经常会使用到分页功能，当然，目前有不少框架（如esayUI）都自带分页的实现，为了更好的理解分页原理，近期本人自己摸索了关于分页查询的一些心得。
归根结底，分页的核心还是在封装PageBean，并通过一定的算法对其进行判断，赋值
public class PageBean<T> implements Serializable{ /** * */ private static final long serialVersionUID = 1L; private int currentPage; //当前第几页 ，请求传过来 private int pageCount; // 每页显示多少条数据 private int totalCount; //总记录数，查询数据获得 private int totalPage; //总页数， 通过 totalCount 和 pageCount计算获得 private int startIndex; //开始索引，与pageCount 组成 limit 条件 private List<T> pageData; //分页显示的页数，如 1,2,3,4 private int start; private int end; public PageBean(int currentPage,int pageCount,int totalCount){ this.currentPage=currentPage; this.pageCount=pageCount; this.totalCount=totalCount; if(totalCount % pageCount==0){ this.totalPage = totalCount/ pageCount; }else{ this.totalPage= totalCount/pageCount+1; } this.startIndex = (currentPage-1)*pageCount; this.start=1; this.end=5; if(pageCount<=5){ this.end= this.totalPage; }else{ this.start=currentPage-2; this.end = currentPage+2; if(start<=0){ this.start=1; this.end=5; } if(this.end > this.totalPage){ this.end=totalPage; this.start=end-4; } } } public int getCurrentPage() { return currentPage; } public void setCurrentPage(int currentPage) { this.currentPage = currentPage; } public int getPageCount() { return pageCount; } public void setPageCount(int pageCount) { this.pageCount = pageCount; } 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 int getStartIndex() { return startIndex; } public void setStartIndex(int startIndex) { this.startIndex = startIndex; } public List<T> getPageData() { return pageData; } public void setPageData(List<T> pageData) { this.pageData = pageData; } public int getStart() { return start; } public void setStart(int start) { this.start = start; } public int getEnd() { return end; } public void setEnd(int end) { this.end = end; } public static long getSerialversionuid() { return serialVersionUID; } }
Controller层
1 int currentPage = Integer.valueOf(request.getParameter("currentPage")); 2 3 int pageCount=7; 4 5 BlogTypeService blogType = new BlogTypeServiceImpl(); 6 7 PageBean<BlogType> page = blogType.page(currentPage, pageCount); 8 request.setAttribute("page", page); 9 request.getRequestDispatcher("/jsp/blogType.jsp").forward(request, response);
service层
public PageBean<BlogType> page(int currentPage,int pageCount) { int totalCount=blogType.getTotal(); PageBean<BlogType> pageBean = new PageBean<>(currentPage, pageCount, totalCount); int startIndex = pageBean.getStartIndex(); pageBean.setPageData(blogType.page(startIndex, pageCount)); return pageBean; }
dao层
public List<BlogType> page(int currentPage,int pageCount){ String sql = "select * from t_blogtype limit ?,?"; PageBean<BlogType> pageBean =null; Connection conn =null; PreparedStatement ps =null; ResultSet rs =null; BlogType blogType =null; try { conn =DBDao.connection(); ps=conn.prepareStatement(sql); ps.setInt(1, currentPage); ps.setInt(2, pageCount); rs=ps.executeQuery(); List<BlogType> list =new ArrayList<BlogType>(); while(rs.next()){ blogType = new BlogType(); blogType.setId(rs.getInt("id")); blogType.setTypeName(rs.getString("typeName")); blogType.setOrderNum(pageCount); list.add(blogType); } return list; } catch (Exception e) { e.printStackTrace(); } return null; } public int getTotal() { String sql ="select count(id) from t_blogtype"; Connection conn =null; PreparedStatement ps=null; ResultSet rs=null; int count=0; try{ conn= DBDao.connection(); ps=conn.prepareStatement(sql); rs=ps.executeQuery(); rs.next(); count=rs.getInt(1); }catch(Exception e){ e.printStackTrace(); } return count; }
因为本文主要在说分页查询，所以关于 数据库的连接就一并放到dao里了！
（其实本人是不知道将数据库的连接放在哪里。。。。嘻嘻）
jsp
1 <body> 2 共有${page.totalCount }个分类,共有${page.pageCount }页，当前为第${page.currentPage }页，每页显示${page.pageCount }条 3 <table align="center" width="100%"> 4 <thead> 5 <th>选择</th> 6 <th>序号</th> 7 <th>博客类别</th> 8 <th>博客排序</th> 9 <th>操作</th> 10 </thead> 11 <tbody align="center" border="1"> 12 <c:forEach items="${page.pageData }" var="page"> 13 <tr> 14 <td><input type="checkbox" name="id"/></td> 15 <td>${page.id }</td> 16 <td>${page.typeName }</td> 17 <td>${page.orderNum }</td> 18 <td><a>修改</a>|<a>删除</a></td> 19 <td></td> 20 </tr> 21 </c:forEach> 22 </tbody> 23 24 </table> 25 <!-- 分页 --> 26 <div style="text-align:center;"> 27 <a href="${pageContext.request.contextPath }/blogType?currentPage=1">首页</a> 28 <!-- 如果当前页为第一页，就没有上一页这个标签 --> 29 <c:if test="${page.currentPage==1 }"> 30 <c:forEach begin="${page.start }" end="${page.end }" step="1" var="i"> 31 <c:if test="${page.currentPage == i}"> 32 ${i} 33 </c:if> 34 <c:if test="${page.currentPage != i}"> 35 <a href="${pageContext.request.contextPath}/blogType?currentPage=${i}">${i}</a> 36 </c:if> 37 </c:forEach> 38 <a href="${pageContext.request.contextPath }/blogType?currentPage=${page.currentPage+1}">下一页</a> 39 </c:if> 40 <!-- 如果不是首页也不是尾页，就与上一页和下一页 --> 41 <c:if test="${page.currentPage>1 && page.currentPage<page.totalPage }"> 42 <a href="${pageContext.request.contextPath }/blogType?currentPage=${page.currentPage-1}">上一页</a> 43 <c:forEach begin="${page.start }" end="${page.end }" step="1" var="i"> 44 <c:if test="${page.currentPage == i}"> 45 ${i} 46 </c:if> 47 <c:if test="${page.currentPage != i}"> 48 <a href="${pageContext.request.contextPath}/blogType?currentPage=${i}">${i}</a> 49 </c:if> 50 </c:forEach> 51 <a href="${pageContext.request.contextPath }/blogType?currentPage=${page.currentPage+1}">下一页</a> 52 </c:if> 53 <!-- 如果是最后一页，则没有下一页 --> 54 <c:if test="${page.currentPage==page.totalPage }"> 55 <a href="${pageContext.request.contextPath }/blogType?currentPage=${page.currentPage-1}">上一页</a> 56 <c:forEach begin="${page.start }" end="${page.end }" step="1" var="i"> 57 <c:if test="${page.currentPage == i}"> 58 ${i} 59 </c:if> 60 <c:if test="${page.currentPage != i}"> 61 <a href="${pageContext.request.contextPath}/blogType?currentPage=${i}">${i}</a> 62 </c:if> 63 </c:forEach> 64 65 </c:if> 66 <a href="${pageContext.request.contextPath }/blogType?currentPage=${page.totalPage}">尾页</a> 67 </div> 68 69 </body>
