Google分页的经典案例

1 、创建 Page 类，

 

 

package cn.csdn.domain; import java.util.List; public class Page { private int nowpage;// 当前页 private int countrecord;// 总记录数 private int countpage;// 总页数 private int pageindex;// 当前页记录开始的位置 (nowpage-1)*PAGESIZE public static final int PAGESIZE = 5;// 每页显示的记录数 private int sumindex = 6;// 索引的sum值 代表的是 google页面中最大显示页数 private int startindex;// 开始的索引值 private int endindex;// 结束的索引值 private List allentities; public Page() { } public Page(int countrecord, int nowpage) { // 可变 // 计算当前页 this.nowpage = nowpage; // 计算出当前页开始的位置 this.pageindex = (nowpage - 1) * PAGESIZE; // 计算总页数 this.countrecord = countrecord; if (this.countrecord % this.PAGESIZE == 0) { this.countpage = this.countrecord / this.PAGESIZE; } else { this.countpage = this.countrecord / this.PAGESIZE + 1; } // 计算索引位置 //==============第一种方法======== /*if (this.nowpage <= 4) { this.startindex = 1; this.endindex = this.nowpage + 2; if(this.endindex>this.countpage){ this.endindex=this.countpage; } }else if(this.nowpage>4){ this.startindex=this.nowpage-3; this.endindex=this.nowpage+2;  if(this.endindex>this.countpage){ this.endindex=this.countpage; this.startindex=this.countpage-5; } }*/ // ============第二种方法========== if(nowpage<(lastpage-2)){  if(nowpage>=5){  //如果大于6的话，startindex要变大 startindex=nowpage-3; }else{ startindex=1; } //endindex要变大 endindex=nowpage+2; // 如果总页数小于6 if(endindex>lastpage){ endindex=lastpage; } }else{  endindex=lastpage; startindex=endindex-5; } // ====================== } //get、set方法 public int getNowpage() { return nowpage; } public void setNowpage(int nowpage) { this.nowpage = nowpage; } public int getCountrecord() { return countrecord; } public void setCountrecord(int countrecord) { this.countrecord = countrecord; } public int getCountpage() { return countpage; } public void setCountpage(int countpage) { this.countpage = countpage; } public int getPageindex() { return pageindex; } public void setPageindex(int pageindex) { this.pageindex = pageindex; } public int getSumindex() { return sumindex; } public void setSumindex(int sumindex) { this.sumindex = sumindex; } public int getStartindex() { return startindex; } public void setStartindex(int startindex) { this.startindex = startindex; } public int getEndindex() { return endindex; } public void setEndindex(int endindex) { this.endindex = endindex; } public List getAllentities() { return allentities; } public void setAllentities(List allentities) { this.allentities = allentities; } } 

 

2 、 dao 方法中的代码：

public int getCountRecord() { // 1、定义返回结果 int countrecord = 0; // 2、获取数据库连接对象 conn = DBConn.getConn(); // 3、创建预处理的sql语句 String sql = "select count(*) from student"; try { // 4、根据预处理的sql语句创建预处理的操作对象 pstmt = conn.prepareStatement(sql); // 5、查询的时候 直接执行 rs = pstmt.executeQuery();  // 6、判断 if (rs.next()) { countrecord = rs.getInt(1); } } catch (SQLException e) { e.printStackTrace(); } finally { DBConn.close(rs, pstmt); } return countrecord; } // 获取当前页信息 public List<Student> getNowPageInfo(int pageindex,int pagesize) { //1、定义返回结果变量 List<Student> allentities = new ArrayList<Student>(); //2、获取连接对象 conn = DBConn.getConn();  try { //3、根据预处理的sql语句创建预处理的操作对象 pstmt = conn.prepareStatement("select id,name,age,email from student limit ?,?"); //4、定义下标变量 并赋值 int index = 1; pstmt.setInt(index++, pageindex); pstmt.setInt(index++, pagesize); //5、查询的时候 直接执行 rs = pstmt.executeQuery(); //判断 while(rs.next()){ //创建实体bean对象 Student entity = new Student(); entity.setId(rs.getInt("id")); entity.setName(rs.getString("name")); entity.setAge(rs.getInt("age")); entity.setEmail(rs.getString("email")); //添加到集合中 allentities.add(entity); }  } catch (SQLException e) { e.printStackTrace(); }finally{ DBConn.close(rs, pstmt); } return allentities; } 

 

3 、在 servlet 中的代码：

protected void doPost(HttpServletRequest req, HttpServletResponse resp)  throws ServletException, IOException { //1.设置编码 req.setCharacterEncoding("utf8"); //2.获取当前页 int nowpage=1; String npage = req.getParameter("nowpage"); if(npage!=null){ nowpage = Integer.valueOf(npage); } //3、创建sevice服务操作对象 StudentServiceImpl ssi = new StudentServiceImpl(); //计算总记录数 int countrecord = ssi.getCountRecord(); //创建page对象 Page stupage = new Page(countrecord, nowpage); //获取当前页信息         List<Student> allentities = ssi.getNowPageInfo(stupage.getPageindex(),stupage.PAGESIZE); //把当前页信息赋值给page对象的list集合 stupage.setAllentities(allentities); //存入到reqeust中 req.setAttribute("stupage", stupage); req.getRequestDispatcher("liststudents.jsp").forward(req, resp); } 

 4 、在 jsp 中的代码 ：

<div id="pg">            <c:if test="${stupage.nowpage!=1}">            <span>              <a href="${pageContext.request.contextPath}/liststudents.do?nowpage=${stupage.nowpage-1>0?stupage.nowpage-1:1}">上一页</a>            </span>            </c:if>         <c:forEach begin="${stupage.startindex}" end="${stupage.endindex}" var="indexnum">            <span>              [<a href="${pageContext.request.contextPath}/liststudents.do?nowpage=${indexnum}">${indexnum}</a>]            </span>          </c:forEach>              <c:if test="${stupage.nowpage!=stupage.countpage}">            <span>            <a href="${pageContext.request.contextPath}/liststudents.do?nowpage=${stupage.nowpage+1>stupage.countpage?stupage.countpage:stupage.nowpage+1}">下一页</a>            </span>            </c:if> </div>