javaBean实现分页显示

import java.sql.*;
import javax.servlet.http.*;
import database.GetConnection;

public class PageQuery {

  int offset; // 记录偏移量

  int total; // 记录总数


  int maxline; // 记录每页显示记录数

  ResultSet rs; // 读出的结果


  int tpages; // 总页数

  int cpages; // 当前页数

  String pagequery; // 分页显示要传递的参数

  String query; // query 语句

  String querypart; // " from " 以后的 query 部分

  String str= "";
  String str1= "";
  String filepath;

  Connection conn; // object of dbclass


  //constructer do nothing

  public PageQuery() throws Exception{
    // 每页显示十行

    maxline = 10;
    conn=(Connection)new GetConnection().getConnection();
  }

  //********读取记录***************

  //　主要工作函数，根据所给的条件从表中读取相应的记录


  public ResultSet myquery(String category,String name,HttpServletRequest req) throws SQLException {

    String query_part, os;
    int begin;
    String query = "select * from " + name + " where category='" + category + "' order by id desc";
    // 截取 " from " 以后的 query 语句

    begin = query.indexOf("from");
    query_part = query.substring(begin, query.length()).trim();

    // 计算偏移量

    os = req.getParameter("offset");
    if (os == null) offset = 0;
    else offset = Integer.parseInt(os);

    // 获取文件名

    filepath = req.getRequestURI();

    querypart = query_part;

    // 计算总的记录条数

    String sql = "select count(*) as total " + this.querypart;
    PreparedStatement psmt=conn.prepareStatement(sql);

    rs = psmt.executeQuery(sql);
    if (rs.next())
    total = rs.getInt(1);

    // 设置当前页数和总页数

    tpages = (int)Math.ceil((double)this.total/this.maxline);
    cpages = (int)Math.floor((double)offset/this.maxline+1);

    // 根据条件判断，取出所需记录

    if (total > 0) {
      sql = query + " limit " + offset + " , " + maxline;
      psmt=conn.prepareStatement(sql);
      rs = psmt.executeQuery(sql);
    }
    return rs;
  }

  // 显示总页数

  public int gettotalpages() {
    return tpages;
  }

  //显示当前所在页数

  public int getcurrenpages() {
    return cpages;
  }
  public ResultSet myqueryEM(HttpServletRequest req) throws SQLException {

     String query_part, os;
     int begin;
     String query = "select * from employee order by id desc";
     // 截取 " from " 以后的 query 语句

     begin = query.indexOf("from");
     query_part = query.substring(begin, query.length()).trim();

     // 计算偏移量

     os = req.getParameter("offset");
     if (os == null) offset = 0;
     else offset = Integer.parseInt(os);

     // 获取文件名

     filepath = req.getRequestURI();

     querypart = query_part;

     // 计算总的记录条数

     String sql = "select count(*) as total " + this.querypart;
     PreparedStatement psmt=conn.prepareStatement(sql);

     rs = psmt.executeQuery(sql);
     if (rs.next())
     total = rs.getInt(1);

     // 设置当前页数和总页数

     tpages = (int)Math.ceil((double)this.total/this.maxline);
     cpages = (int)Math.floor((double)offset/this.maxline+1);

     // 根据条件判断，取出所需记录

     if (total > 0) {
     sql = query + " limit " + offset + " , " + maxline;
     psmt=conn.prepareStatement(sql);
     rs = psmt.executeQuery(sql);
     }
     return rs;
     }

  //**********显示翻页提示栏*************

  // 显示首页、下页、上页、尾页

  // 你可以改成你喜欢的样式

  public String pagelegend() {


     int first, next, prev, last;
     first = 0;
     next = offset + maxline;


     prev = offset - maxline;
     last = (this.tpages - 1) * maxline;

     if(offset >= maxline)
     str += " + filepath + "?offset=" + first + ">首页 ";
     else str += " 首页 ";
     if(prev >= 0)
     str += " + filepath + "?offset=" + prev + ">前页 ";
     else str += " 前页 ";
     if(next < total)
     str += " + filepath + "?offset=" + next + ">后页 ";
     else str += " 后页 ";
     if(tpages != 0 && cpages < tpages)
     str += " + filepath + "?offset=" + last + ">尾页";
     else str += " 尾页 ";

     str += " 页次：" + getcurrenpages() + "/" + gettotalpages() + "页 ";
     str += maxline + "条/页 " + "共" + total + "条";
     return str;
     }
}