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java操作数据库:分页查询
直接上。。。。
还是用之前的goods表,增加了一些数据
1、实体类Goods
// 封装数据 public class Goods { private int gid; private String gname; private String gprice; private String gdate; public int getGid() { return gid; } public void setGid(int gid) { this.gid = gid; } public String getGname() { return gname; } public void setGname(String gname) { this.gname = gname; } public String getGprice() { return gprice; } public void setGprice(String gprice) { this.gprice = gprice; } public String getGdate() { return gdate; } public void setGdate(String gdate) { this.gdate = gdate; } public Goods(int gid, String gname, String gprice, String gdate) { super(); this.gid = gid; this.gname = gname; this.gprice = gprice; this.gdate = gdate; } public Goods() { super(); } }
2、DBHelper类
import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.Statement; /** * 获取数据库操作的连接对象 * 关闭数据库操作的各种资源 * @author 晏先政 * */ public class DBHelper { private static final String className = "com.mysql.jdbc.Driver"; private static final String url = "jdbc:mysql://localhost:3306/test?characterEncoding=utf8&useSSL=true"; private static final String uname = "root"; private static final String upass = ""; /** * 获取数据库连接对象的方法 */ public static Connection getConn(){ Connection conn = null; try{ Class.forName(className); conn = DriverManager.getConnection(url,uname, upass); } catch(Exception e){ e.printStackTrace(); } return conn; } /** * 关闭数据库连接对象 */ public static void closeConn(Connection conn){ try{ if(conn!=null){ conn.close(); } } catch(Exception e){ e.printStackTrace(); } } /** * 关闭数据库操作对象 */ public static void closeStmt(Statement stmt){ try{ if(stmt!=null){ stmt.close(); } } catch(Exception e){ e.printStackTrace(); } } /** * 关闭数据库操作对象 */ public static void closePstmt(PreparedStatement pstmt){ try{ if(pstmt!=null){ pstmt.close(); } } catch(Exception e){ e.printStackTrace(); } } /** * 关闭数据库操作对象 */ public static void closeRs(ResultSet rs){ try{ if(rs!=null){ rs.close(); } } catch(Exception e){ e.printStackTrace(); } } }
3、实现类GoodsDao:操作数据库进行查询
import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.util.ArrayList; import java.util.List; public class GoodsDao { private Connection conn = null; private PreparedStatement pstmt = null; private ResultSet rs = null; // 查询当前页的数据 public List<Goods> getListByCurPage(int curPage){ List<Goods> list = new ArrayList<Goods>(); try{ conn = DBHelper.getConn(); int num = (curPage-1)*5; String sql = "select * from goods limit "+num+",5"; pstmt = conn.prepareStatement(sql); rs = pstmt.executeQuery(); while(rs.next()){ Goods ba = new Goods(rs.getInt("gid"),rs.getString("gname"),rs.getString("gprice"),rs.getString("gdate")); ba.setGid(rs.getInt("gid")); list.add(ba); } } catch(Exception e){ e.printStackTrace(); } finally{ DBHelper.closeRs(rs); DBHelper.closePstmt(pstmt); DBHelper.closeConn(conn); } return list; } // 查询所有记录的总条数 public int getCount(){ int i = 0; try{ conn = DBHelper.getConn(); String sql = "select count(*) cnt from goods"; pstmt = conn.prepareStatement(sql); rs = pstmt.executeQuery(); if(rs.next()){ i = rs.getInt("cnt"); } } catch(Exception e){ e.printStackTrace(); } finally{ DBHelper.closeRs(rs); DBHelper.closePstmt(pstmt); DBHelper.closeConn(conn); } return i; } }
4、展示类GoodsShow
import java.util.List; import java.util.Scanner; public class GoodsShow { public static void main(String[] args) { GoodsShow bs = new GoodsShow(); bs.show(); } private Scanner input = new Scanner(System.in); private GoodsDao dao = new GoodsDao(); int curPage = 1; List<Goods> list = null; public void show(){ int rowCount = dao.getCount(); int pageCount = rowCount%5==0?rowCount/5:rowCount/5+1; list = dao.getListByCurPage(curPage); print(list); System.out.println("首页【F】上一页【P】下一页【N】尾页【L】请选择:"); char choose = input.next().toUpperCase().charAt(0); switch(choose){ case ‘F‘: curPage = 1; break; case ‘P‘: curPage = curPage -1; if(curPage<1){ curPage = 1; } break; case ‘N‘: curPage = curPage +1; if(curPage>pageCount){ curPage = pageCount; } break; case ‘L‘: curPage = pageCount; break; } show(); } public void print(List<Goods> list){ System.out.println("编号\t商品\t价格\t时间"); for(int i=0;i<list.size();i++){ System.out.println(list.get(i).getGid()+"\t"+list.get(i).getGname()+"\t"+list.get(i).getGprice()+"\t"+list.get(i).getGdate()); } } }
then。。。。
java操作数据库:分页查询
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