前台dao 接口与实现 ProductsClassifyDao

package cn.client.dao;

import java.util.List;
import cn.entity.ProductsClassify;
/*
 * 商品类型表 DAO 接口
 * */
public interface ProductsClassifyDao {
	//商品类型表列表
	public List<ProductsClassify> productsClassifyList();
	
	//根据名称获得对应的值
	public int selectKey(String productsClassifyContent);
	
	//根据值找到name
	public String selectName(int productsClassifyId);
}

 

package cn.client.dao.impl;

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

import cn.client.dao.BaseDao;
import cn.client.dao.ProductsClassifyDao;
import cn.entity.ProductsClassify;
/*
 * 商品类型表 DAO 实现
 * */
public class ProductsClassifyDaoImpl extends BaseDao implements
ProductsClassifyDao {
	Connection conn = null;//数据库连接  
	PreparedStatement pstmt = null;//数据库操作  
	ResultSet rs = null;//保存查询结果  
	public List<ProductsClassify> productsClassifyList() {
		List<ProductsClassify> productsClassifyList = new ArrayList<ProductsClassify>();
		ProductsClassify item = null;
		String sql = "select products_classify_id, products_classify_content from products_classify order by products_classify_id asc";
		conn=this.getConnection();
		try {
			pstmt = conn.prepareStatement(sql);
			rs = pstmt.executeQuery();
			while(rs.next()){
				item = new ProductsClassify(
						rs.getInt(1),
						rs.getString(2)
						);
				productsClassifyList.add(item);
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			this.closeAll(conn, pstmt, rs);
		}
		return productsClassifyList;
	}

	//根据名称获得对应的值
	public int selectKey(String productsClassifyContent){
		String sql = "select products_classify_id from " +
				"products_classify where products_classify_content=?";
		int key = 0;
		conn=this.getConnection();
		try {
			pstmt = conn.prepareStatement(sql);
			pstmt.setString(1, productsClassifyContent);
			rs = pstmt.executeQuery();
			if(rs.next()){
				key = rs.getInt(1);
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			this.closeAll(conn, pstmt, rs);
		}
		return key;
	}

	//根据值找到name
	public String selectName(int productsClassifyId){
		String sql = "select products_classify_content from products_classify" +
				" where products_classify_id = ?";
		String name = null;
		conn=this.getConnection();
		try {
			pstmt = conn.prepareStatement(sql);
			pstmt.setInt(1, productsClassifyId);
			rs = pstmt.executeQuery();
			if(rs.next()){
				name = rs.getString(1);
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			this.closeAll(conn, pstmt, rs);
		}
		return name;
	}
}