categorydao.java

一个简易的网上书店（jsp+sqlservler+struts）。

package com.webshop.db;
import java.sql.*;
import com.webshop.domain.Category;
import com.webshop.exception.ActionException;
/**
 * @author w
 *
 * To change this generated comment edit the template variable "typecomment":
 * Window>Preferences>Java>Templates.
 * To enable and disable the creation of type comments go to
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 */
public class CategoryDAO {

	Connection con;//数据库连接
	String selectAllCategory="select * from category";
	String selectCategoryById="select * from category where catid=?";
	
	/**
	 * Constructor for CategoryDAO.
	 */
	public CategoryDAO() {
		super();
	}
	
	/**
	 * 根据ID查找商品信息
	 */
	public Category getCategoryById(String id)
	{
		Category category=null;
		try
		{
			con=DatabaseConnection.getConnection();
		}
		catch(Exception e)
		{
			throw new ActionException("不能获得连接，"+e.getMessage());
		}
		try
		{
			PreparedStatement pstmt=con.prepareStatement(selectCategoryById);
			pstmt.setString(1,id);
			ResultSet rst=pstmt.executeQuery();
          
			if(rst.next())
			{
				category=new Category();
				category.setCategoryId(rst.getString("catid"));
				category.setName(rst.getString("name"));
				category.setDescription(rst.getString("descn"));
			}
				con.close();
		}
		catch(SQLException e)
		{
			 throw new ActionException("执行数据库操作发生错误，"+e.getMessage());
		}
		finally
		{
			try
			{
				if(con!=null)
				con.close();
			}
			catch(Exception e2)
			{
			}
		}
		return category;
	}			
	
	/**
	 * 获得所有的商品类别
	 * @return Collection 
	 */
	public java.util.Collection getAllCategory()
	{
		java.util.Collection categoryes=new java.util.ArrayList();
		try
		{
			con=DatabaseConnection.getConnection();
		}
		catch(Exception e)
		{
			throw new ActionException("不能获得连接，"+e.getMessage());
		}
		try
		{
			PreparedStatement pstmt=con.prepareStatement(selectAllCategory);
			ResultSet rst=pstmt.executeQuery();
            Category category;
			while(rst.next())
			{
				category=new Category();
				category.setCategoryId(rst.getString("catid"));
				category.setName(rst.getString("name"));
				category.setDescription(rst.getString("descn"));
				categoryes.add(category);
			}
				con.close();
		}
		catch(SQLException e)
		{
			 throw new ActionException("执行数据库操作发生错误，"+e.getMessage());
		}
		finally
		{
			try
			{
				if(con!=null)
				con.close();
			}
			catch(Exception e2)
			{
			}
		}
		return categoryes;
	}			

}