msgboarddao.java

java开发中的 数据分页

package com.jgxy.dao;


import java.sql.Connection;
import java.sql.Date;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

import com.jgxy.bean.Msgboard;
import com.jgxy.util.DBUtil;

public class MsgboardDAO {
	/**
	 * 查找记录
	 */
	public List<Msgboard> getScrollData(int firstindex,int maxresult){
		Connection conn=null;
		ResultSet rs=null;
		conn=DBUtil.getConnection();
		//记录列表
		List<Msgboard> list=new ArrayList<Msgboard>();
		
		//分页查询
		String sql="select * from msgboard limit ?,?";
		
		PreparedStatement pstmt=DBUtil.getPreparedStatement(conn, sql);

		try{
			pstmt.setInt(1, firstindex);
			pstmt.setInt(2, maxresult);
			rs=pstmt.executeQuery();
			while(rs.next()){
				//将rs中的结果取出来，存入QueryResult
				int vid=rs.getInt("id");
				String vsubject=rs.getString("subject");
				String vquestion=rs.getString("question");
				String vquestioner=rs.getString("questioner");
				Date vquestiondate=rs.getDate("questiondate");
				
				Msgboard m=new Msgboard();
				m.setId(vid);
				m.setSubject(vsubject);
				m.setQuestion(vquestion);
				m.setQuestioner(vquestioner);
				m.setQuestiondate(vquestiondate);
				//把留言列表加入list列表中
				list.add(m);
			}			
		}catch(SQLException e){
			e.printStackTrace();
		}finally{
			DBUtil.closeRs(rs);
			DBUtil.closeStm(pstmt);
			DBUtil.closeConn(conn);
		}
		return list;
	}
	/**
	 * 统计数据库中有多少条记录
	 * @return
	 */
	public int getCount(){
		int count=0;
		String sql="select count(*) from msgboard";
		Connection conn=DBUtil.getConnection();
		Statement stmt=DBUtil.getStatement(conn); 
		ResultSet rs=DBUtil.getResultSet(stmt, sql);
		try{
			if(rs.next()){
				count=rs.getInt(1);
			}
		}
		catch(SQLException e){
			e.printStackTrace();
		}finally{
			DBUtil.closeRs(rs);
			DBUtil.closeStm(stmt);
			DBUtil.closeConn(conn);
		}
		return count;
	}
	
	/**
	 * 保存记录
	 */
	public void save(Msgboard msgboard){
		Connection conn=null;
		PreparedStatement pstmt=null;
		String sql="insert msgboard (subject,questioner,question,questiondate) values(?,?,?,?)";
		conn=DBUtil.getConnection();
		pstmt=DBUtil.getPreparedStatement(conn, sql);
		
		try{
			pstmt.setString(1, msgboard.getSubject());
			pstmt.setString(2, msgboard.getQuestioner());
			pstmt.setString(3, msgboard.getQuestion());
			pstmt.setDate(4, new Date(System.currentTimeMillis()));
			
			pstmt.executeUpdate();
		}catch(SQLException e){
			e.printStackTrace();
		}
		
	}
		
}