商品浏览系统之业务逻辑类的实现

一 业务逻辑类（DAO）

package dao;

import java.sql.Connection;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.util.ArrayList;

import util.DBHelper;

import entity.Items;

//商品的业务逻辑类

public class ItemsDAO {

    // 获得所有的商品信息

    public ArrayList<Items> getAllItems() {

        Connection conn = null;

        PreparedStatement stmt = null;

        ResultSet rs = null;

        ArrayList<Items> list = new ArrayList<Items>(); // 商品集合

        try {

            conn = DBHelper.getConnection();

            String sql = "select * from items;"; // SQL语句

            stmt = conn.prepareStatement(sql);

            rs = stmt.executeQuery();

            while (rs.next()) {

                Items item = new Items();

                item.setId(rs.getInt("id"));

                item.setName(rs.getString("name"));

                item.setCity(rs.getString("city"));

                item.setNumber(rs.getInt("number"));

                item.setPrice(rs.getInt("price"));

                item.setPicture(rs.getString("picture"));

                list.add(item);// 把一个商品加入集合

            }

            return list; // 返回集合。

        } catch (Exception ex) {

            ex.printStackTrace();

            return null;

        } finally {

            // 释放数据集对象

            if (rs != null) {

                try {

                    rs.close();

                    rs = null;

                } catch (Exception ex) {

                    ex.printStackTrace();

                }

            }

            // 释放语句对象

            if (stmt != null) {

                try {

                    stmt.close();

                    stmt = null;

                } catch (Exception ex) {

                    ex.printStackTrace();

                }

            }

        }

    }

    // 根据商品编号获得商品资料

    public Items getItemsById(int id) {

        Connection conn = null;

        PreparedStatement stmt = null;

        ResultSet rs = null;

        try {

            conn = DBHelper.getConnection();

            String sql = "select * from items where id=?;"; // SQL语句

            stmt = conn.prepareStatement(sql);

            stmt.setInt(1, id);

            rs = stmt.executeQuery();

            if (rs.next()) {

                Items item = new Items();

                item.setId(rs.getInt("id"));

                item.setName(rs.getString("name"));

                item.setCity(rs.getString("city"));

                item.setNumber(rs.getInt("number"));

                item.setPrice(rs.getInt("price"));

                item.setPicture(rs.getString("picture"));

                return item;

            } else {

                return null;

            }

        } catch (Exception ex) {

            ex.printStackTrace();

            return null;

        } finally {

            // 释放数据集对象

            if (rs != null) {

                try {

                    rs.close();

                    rs = null;

                } catch (Exception ex) {

                    ex.printStackTrace();

                }

            }

            // 释放语句对象

            if (stmt != null) {

                try {

                    stmt.close();

                    stmt = null;

                } catch (Exception ex) {

                    ex.printStackTrace();

                }

            }

        }

    }

    //获取最近浏览的前五条商品信息

    public ArrayList<Items> getViewList(String list)

    {

        System.out.println("list:"+list);

        ArrayList<Items> itemlist = new ArrayList<Items>();

        int iCount=5; //每次返回前五条记录

        if(list!=null&&list.length()>0)

        {

            String[] arr = list.split(",");

            System.out.println("arr.length="+arr.length);

            //如果商品记录大于等于5条

            if(arr.length>=5)

            {

               for(int i=arr.length-1;i>=arr.length-iCount;i--)

               {

                  itemlist.add(getItemsById(Integer.parseInt(arr[i])));  

               }

            }

            else

            {

                for(int i=arr.length-1;i>=0;i--)

                {

                    itemlist.add(getItemsById(Integer.parseInt(arr[i])));

                }

            }

            return itemlist;

        }

        else

        {

            return null;

        }

        

    }

 

}